Article

Paternity analysis in a litter of whale shark embryos

Authors:
  • Shark Research Institute
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Abstract

A 10.6 m female whale shark Rhincodon typus caught off the coast of eastern Taiwan in 1995 carried 304 embryos that ranged in developmental stage from individuals still in egg cases to hatched and free-swimming near-term animals. This litter established that whale sharks develop by aplacental yolk-sac viviparity, with embryos hatching from eggs within the female. The range of developmental stages in this litter suggested ongoing fertilization over an extended period of time, with embryos of different ages possibly sired by different males. A series of 9 microsatellite markers for R. typus have now been used to investigate paternity in a subset of these embryos. We determined the paternity of 29 embryos representing 10% of the original litter, and spanning most of the range of size and developmental stage of the 304 embryos. All were full siblings sired by the same male, suggesting that this male may have sired the entire litter. Probability analysis indicates that a second male could go undetected if it sired less than 10% of the litter. The range of developmental stages of embryos from this single sire further suggests that female whale sharks may have the ability to store sperm for later fertilization. In the absence of any tissue to determine parental genotypes, maternal mitochondrial sequence was obtained from the embryos, identifying a novel haplotype linked to those from the western Indian Ocean. This finding adds further support for the global population structure emerging for R. typus.

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... One theory suggests that MP increases the effective population size (due to the increase in males that can mate successfully) and thereby reduces the loss of allelic diversity. The more the male engages in polyandrous behaviour, the more offspring it will sire and the greater its reproductive fitness will be (Daly-Engel et al., 2006Schmidt et al., 2010). Furthermore, increased genetic variation within the offspring would increase the likelihood of more offspring being able to survive in fluctuating environmental conditions. ...
... Furthermore, increased genetic variation within the offspring would increase the likelihood of more offspring being able to survive in fluctuating environmental conditions. Multiple paternities could therefore buffer against the loss of genetic diversity brought on by the slow molecular evolution rate and k-selected life-history traits in sharks (Schmidt et al., 2010). Contradictory to this, the second theory states that although MP might increase genetic variability within single litters, effective population size is reduced within populations due to an increase of variable male reproductive success (Daly-Engel et al., 2010;Schmidt et al., 2010). ...
... Multiple paternities could therefore buffer against the loss of genetic diversity brought on by the slow molecular evolution rate and k-selected life-history traits in sharks (Schmidt et al., 2010). Contradictory to this, the second theory states that although MP might increase genetic variability within single litters, effective population size is reduced within populations due to an increase of variable male reproductive success (Daly-Engel et al., 2010;Schmidt et al., 2010). This is due to males siring fewer offspring during multiple matings than would have been possible with monandry (Daly-Engel et al., 2010;Schmidt et al., 2010). ...
Article
In this study, multiple paternity (MP) was investigated in three commercially important shark species, common smoothhound Mustelus mustelus, dusky shark Carcharhinus obscurus and scalloped hammerhead Sphyrna lewini occurring in southern Africa. Reduced marker panels of between five and six microsatellite loci were constructed for each species and used to genotype and assess the presence of MP in a total of 60 M. mustelus individuals from six litters, 90 C. obscurus individuals from 14 litters and 54 S. lewini individuals from 13 litters. Analysis in GERUD and COLONY revealed the presence of MP in all three species. Multiple paternities were observed in 67, 35 and 46% of the litters of M. mustelus, C. obscurus and S. lewini, with corresponding average sire size of 1·6, 1·4 and 2·0, respectively. The variation in the rate of MP among the three species is in accordance with previous studies whilst the comparatively high frequency of MP observed for M. mustelus, matches what has previously been reported for shark species demonstrating aggregation behaviour.
... Whale sharks are known to segregate by sex and size [3][4][5][6][7][8] and in recent decades several seasonal aggregations have been identified, providing opportunities for a number of studies focused on this species [8][9][10][11][12]. Rowat and Brooks [3] described an aggregation as a site with more than 10 individuals in less than 1 km 2 . ...
... Most of these aggregations comprised immature males (6-8 m Total Length (TL)) and they appear to exist mostly for feeding purposes. Therefore certain aspects of whale shark's biology and ecology remain poorly understood, especially those related to reproduction [3,5,6,13]. Adult female ($9 m TL) [1] and neonate (,1 m TL) published records are scarce, and apparently pregnant females have been only reported consistently in the Gulf of California [7,[14][15][16], Galapagos Islands [17] and Philippines [3]. ...
... To date, most information regarding R. typus population structure comes from coastal aggregations at different locations in the Caribbean Sea, Indian Ocean and the Gulf of California, and these aggregations are dominated by immature males [7,9,10,12,51,52]. In contrast, Galapagos and the southern of the Gulf of California, both in the Tropical Eastern Pacific, are to date the only known locations where consistent sightings of large apparently pregnant individuals have been confirmed [6,7,[14][15][16][17]. However, the presence of possibly pregnant individuals at both locations does not coincide in time nor oceanographic conditions. ...
Article
Full-text available
The life history of the whale shark (Rhincodon typus), including its reproductive ecology, still remains largely unknown. Here, we present results from the first whale shark population study around Darwin Island, Galapagos Marine Reserve. Following a diversified approach we characterized seasonal occurrence, population structure and size, and described habitat use of whale sharks based on fine scale movements around the island. Whale shark presence at Darwin Island was negatively correlated with Sea Surface Temperature (SST), with highest abundance corresponding to a cool season between July and December over six years of monitoring. From 2011 to 2013 we photo-identified 82 whale sharks ranging from 4 to 13.1 m Total Length (TL). Size distribution was bimodal, with a great majority (91.5%) of adult female individuals averaging 11.35 m±0.12 m (TL±SE), all but one showing signs of a potential pregnancy. Population dynamics models for apparently pregnant sharks estimated the presence of 3.76±0.90 (mean ± SE) sharks in the study area per day with an individual residence time of 2.09±0.51 (mean ± SE) days. Movement patterns analysis of four apparently pregnant individuals tracked with acoustic tags at Darwin Island revealed an intense use of Darwin's Arch, where no feeding or specific behavior has been recorded, together with periodic excursions around the island's vicinity. Sharks showed a preference for intermediate depths (20-30 m) with occasional dives mostly to mid-water, remaining the majority of their time at water temperatures between 24-25°C. All of our results point to Darwin Island as an important stopover in a migration, possibly with reproductive purposes, rather than an aggregation site. Current studies carried out in this area to investigate regional scale movement patterns may provide essential information about possible pupping grounds for this enigmatic species.
... Whale sharks are known to segregate by sex and size [3][4][5][6][7][8] and in recent decades several seasonal aggregations have been identified, providing opportunities for a number of studies focused on this species [8][9][10][11][12]. Rowat and Brooks [3] described an aggregation as a site with more than 10 individuals in less than 1 km 2 . ...
... Most of these aggregations comprised immature males (6-8 m Total Length (TL)) and they appear to exist mostly for feeding purposes. Therefore certain aspects of whale shark's biology and ecology remain poorly understood, especially those related to reproduction [3,5,6,13]. Adult female ($9 m TL) [1] and neonate (,1 m TL) published records are scarce, and apparently pregnant females have been only reported consistently in the Gulf of California [7,[14][15][16], Galapagos Islands [17] and Philippines [3]. ...
... To date, most information regarding R. typus population structure comes from coastal aggregations at different locations in the Caribbean Sea, Indian Ocean and the Gulf of California, and these aggregations are dominated by immature males [7,9,10,12,51,52]. In contrast, Galapagos and the southern of the Gulf of California, both in the Tropical Eastern Pacific, are to date the only known locations where consistent sightings of large apparently pregnant individuals have been confirmed [6,7,[14][15][16][17]. However, the presence of possibly pregnant individuals at both locations does not coincide in time nor oceanographic conditions. ...
Conference Paper
Background The Galapagos Whale Shark Project is a multi-institutional effort initiated in 2011 with the aim to characterize the presence, population structure and movement patterns of whale sharks within and around the Galapagos Marine Reserve. This specific study aimed to understand their occurrence, residency and habitat use around Darwin Island, located at the northern tip of the Galapagos Archipelago, where large individuals had been reported to be seasonally abundant. Approach This study followed a diversified methodology approach that included: analysis of a local underwater visual census database of pelagic species (2007–2013) to establish seasonality in their occurrence; specific whale shark surveys (2011–2013) to collect information about shark's size (laser photogrammetry), sex, behavior and signs of potential pregnancy; photo-ID records (2011–2013) obtained during these surveys to determine residency and abundance; and the deployment of acoustic tags for continuous tracking around Darwin Island to assess habitat use at the study site. Results Whale shark presence at Darwin Island follows a seasonal pattern. During the cool season (July–December), a strongly female-biased whale shark population, composed mostly (91.8%) by large individuals (11.35 m ± 0.12 m (TL ± SE)), pass through the study site. The great majority of these individuals show clear distended bellies, which could be a sign of a potential pregnancy. Population dynamics models for these apparently pregnant sharks estimated the presence of 3.76 ± 0.90 (mean±SE) sharks in the study area per day with an individual residence time of 2.09 ± 0.51 (mean±SE) days. Assuming constancy in these rates for the entire cool season, we can estimate a net abundance of 695 ± 166 (SE; 95%CI 442–1110) apparently pregnant whale sharks per season. Movement patterns analysis of four apparently pregnant individuals revealed an intense use of Darwin's Arch, where no feeding or specific behavior has been recorded or could be inferred from their dive profiles, together with periodic excursions around the island's vicinity. Sharks showed a preference for intermediate depths (20–30 m) with occasional dives mostly to mid-water, remaining the majority of their time at water temperatures between 24–25°C. Conclusions The lack of evidence of specific behavior observed at Darwin Island, together with the short residence time and strong intra-seasonal abundance and high turnover rate, indicate that this location is not an aggregation site but an important stopover in a migration. In the case of adult R. typus individuals observed, this migration might involve reproductive purposes, as all but one were apparently gravid.
... It was first described to science in 1828 (Smith, 1828) but despite its status as the largest fish in the sea, by 1985, over 150 years later, there were only 320 records of this species (Wolfson, 1986). Similarly, while specimens had been dissected, much of its biology and habits remained uncertain, including its method of reproduction (Colman, 1997a;Stevens, 2007) prompting its description as enigmatic ('mysterious or difficult to understand' Oxford dictionary) by some researchers (Norman & Catlin, 2007;Schmidt et al., 2010). In certain locations R. typus are known to occur on a predictable, seasonal basis (Anderson & Ahmed, 1993;Alava et al., 1997a;Eckert & Stewart, 2001;Eckert et al., 2002) and in some †Author to whom correspondence should be addressed. ...
... A total of 237 embryos from the Taiwanese litter were sexed, 114 were male and 123 were female indicating a normal 50:50 sex ratio at birth (Joung et al., 1996;Leu et al., 1997). Recent genetic analysis of 29 of the pups of various sizes, found that all had the same father (Schmidt et al., 2010). This provides strong evidence that a single male sired the entire litter (monoandry), although probability analysis suggested it was feasible that another male might have sired <10% of these 300 pups. ...
... They concluded that, although the sample size was small, it was likely that there was significant gene flow and thus segregated breeding populations were unlikely. In a further genetic study of a sample of the embryos from the Taiwanese female, Schmidt et al. (2010) also identified another haplotype from the mitochondrial control region bringing the current total identified for R. typus to 45. ...
Article
Although the whale shark Rhincodon typus is the largest extant fish, it was not described until 1828 and by 1986 there were only 320 records of this species. Since then, growth in tourism and marine recreation globally has lead to a significant increase in the number of sightings and several areas with annual occurrences have been identified, spurring a surge of research on the species. Simultaneously, there was a great expansion in targeted R. typus fisheries to supply the Asian restaurant trade, as well as a largely un-quantified by-catch of the species in purse-seine tuna fisheries. Currently R. typus is listed by the IUCN as vulnerable, due mainly to the effects of targeted fishing in two areas. Photo-identification has shown that R. typus form seasonal size and sex segregated feeding aggregations and that a large proportion of fish in these aggregations are philopatric in the broadest sense, tending to return to, or remain near, a particular site. Somewhat conversely, satellite tracking studies have shown that fish from these aggregations can migrate at ocean-basin scales and genetic studies have, to date, found little graphic differentiation globally. Conservation approaches are now informed by observational and environmental studies that have provided insight into the feeding habits of the species and its preferred habitats. Notwithstanding these advances, there remain notable gaps in the knowledge of this species particularly with respect to the life history of neonates and adults who are not found in the feeding aggregations.
... Interestingly, records of whale shark neonates are limited, and pupping and nursery areas remain unidentified (Rowat and Brooks 2012). It has to be noted, however, that some species of shark do not use geographically restricted nurseries, and pupping may occur over large geographic areas (Heupel et al. 2007), especially for whale sharks given the way the young appear to develop (see Schmidt et al. 2010 Within each of the 20 global hotspots, the percentage of individually identified sharks that were observed in 2 or more years was calculated (table 1). Belize exhibited the greatest percentage of returning individuals (76.6% of the 47 individual sharks identified), followed by the Maldives (60.4% of 101 sharks) and South Africa (60.0% of 45 sharks), whereas whale sharks from the Galapagos Islands showed the least evidence for site fidelity, with only 1 of 141 identified sharks resighted in any year subsequent to initial identification (table 1). ...
... shark-doing-in-a-maldives-swimmingpool), combined with the capture of the pregnant individual off Taiwan (Joung et al. 1996), may indicate a pupping area close to these locations. However, staggered (see Schmidt et al. 2010) and potentially long gestation strongly argues against specific pupping grounds, as does the fact that any neonates found have been singles and perhaps doubles at most. Hueter and colleagues (2013), colleagues (2007, 2012a), Ketchum and colleagues (2013), and Hsu and colleagues (2014b) have suggested that offshore habitats may provide pupping and nursery areas for whale sharks. ...
Article
Full-text available
The whale shark is an ideal flagship species for citizen science projects because of its charismatic nature, its size, and the associated ecotourism ventures focusing on the species at numerous coastal aggregation sites. An online database of whale shark encounters, identifying individuals on the basis of their unique skin patterning, captured almost 30,000 whale shark encounter reports from 1992 to 2014, with more than 6000 individuals identified from 54 countries. During this time, the number of known whale shark aggregation sites (hotspots) increased from 13 to 20. Examination of photo-identification data at a global scale revealed a skewed sex-ratio bias toward males (overall, more than 66%) and high site fidelity among individuals, with limited movements of sharks between neighboring countries but no records confirming large, ocean basin-scale migrations. Citizen science has been vital in amassing large spatial and temporal data sets to elucidate key aspects of whale shark life history and demographics and will continue to provide substantial long-term value.
... The world's largest fish, the whale shark, Rhincodon typus (Smith, 1828), has routinely been described as enigmatic [1,2], as aspects of its biology and habitat use remain poorly understood. For example, knowledge of the species' reproduction is lacking [2,3] and encounters with neonates are a rare occurrence [3,4]. ...
... The world's largest fish, the whale shark, Rhincodon typus (Smith, 1828), has routinely been described as enigmatic [1,2], as aspects of its biology and habitat use remain poorly understood. For example, knowledge of the species' reproduction is lacking [2,3] and encounters with neonates are a rare occurrence [3,4]. Whale sharks routinely move across international boundaries and political jurisdictions [5][6][7][8][9]. ...
Article
Full-text available
The Arabian Gulf is the warmest sea in the world and is host to a globally significant population of the whale shark Rhincodon typus. To investigate regional whale shark behaviour and movements, 59 satellite-linked tags were deployed on whale sharks in the Al Shaheen area off Qatar from 2011-14. Four different models of tag were used throughout the study, each model able to collect differing data or quantities of data. Retention varied from one to 227 days. While all tagged sharks crossed international maritime boundaries, they typically stayed within the Arabian Gulf. Only nine sharks dispersed through the narrow Strait of Hormuz into the Gulf of Oman. Most sharks stayed close to known or suspected feeding aggregation sites over summer months, but dispersed throughout the Arabian Gulf in winter. Sharks rarely ventured into shallow areas (
... All rights reserved network option (Bandelt, Forster & Rohl, 1999). To compare the haplotype frequencies detected in this study to global frequencies, we used the previously published Qatar tissue haplotype frequencies, as well as the global DL1 reference list compiled by Sigsgaard et al. (2016) using the literature (Alam, Petit, Read & Dove, 2014;Castro et al., 2007;Schmidt et al., 2010). To investigate the relationship between the number of sampled sharks and the haplotype diversity recovered, we generated an accumulation curve with extrapolation using the iNEXT package (Hsieh, Ma & Chao, 2016). ...
... Interestingly, when direct comparisons were possible, we found similar frequencies of the two dominant haplotypes (DL1-A and DL1-B), which contrasted the clear dominance of DL1-A that has been widely reported elsewhere (Alam, Petit, Read & Dove, 2014;Castro et al., 2007;Schmidt et al., 2010;Sigsgaard et al., 2016). Such differences in allele frequencies would generally imply significant genetic differentiation of the Ningaloo population, however results from other population genetic studies based on both microsatellites and mtDNA data suggest panmixia of shark populations across ocean basins (Castro et al., 2007;Schmidt et al., 2009;Vignaud et al., 2014). ...
Article
Population genetic data can provide valuable information on the demography of a species. For rare and elusive marine megafauna, samples for generating the data are traditionally obtained from tissue biopsies, which can be logistically difficult and expensive to collect and require invasive sampling techniques. Analysis of environmental DNA (eDNA) offers an alternative, minimally invasive approach to provide important genetic information. Although eDNA approaches have been studied extensively for species detection and biodiversity monitoring in metabarcoding studies, the potential for the technique to address population‐level questions remains largely unexplored. Here, we applied “eDNA haplotyping” to obtain estimates of the intraspecific genetic diversity of a whale shark (Rhincodon typus) aggregation at Ningaloo reef, Australia. Over two weeks, we collected seawater samples directly behind individual sharks prior to taking a tissue biopsy sample from the same animal. Our data showed a 100% match between mtDNA sequences recovered in the eDNA and tissue sample for all 28 individuals sampled. In the seawater samples, >97% of all reads were assigned to six dominant haplotypes, and a clear dominant signal (~99% of sample reads) was recovered in each sample. Our study demonstrates accurate individual‐level haplotyping from seawater eDNA. When DNA from one individual clearly dominates each eDNA sample, it provides many of the same opportunities for population genetic analyses as a tissue sample, potentially removing the need for tissue sampling. Our results show that eDNA approaches for population‐level analyses have the potential to supply critical demographic data for the conservation and management of marine megafauna.
... The mitochondrial control regions of whale sharks generated using iDNA were combined with 613 sequences published by previous studies of whale shark populations (Castro et al., 2007;Ramírez-Macías et al., 2007;Schmidt et al., 2010;Vignaud et al., 2014). Identical iDNA sequences from the same whale shark host were removed prior to genetic analysis, to eliminate the chance of biasing estimates of population genetic differentiation (Supplementary Table 1). ...
... Haplotype clustering confirmed a 100% sequence match for DNA sequences amplified from copepods collected from the same whale shark host (Supplementary Data 1). An initial alignment of the 31 newly-generated iDNA control region sequences with the 613 sequences provided by previous studies (Castro et al., 2007;Schmidt et al., 2010;Vignaud et al., 2014;Walter and Boxshall, 2017) yielded a 1,910 bp product (Supplementary Data 2). Trimming using 5 ′and 3 ′ -ends produced a final alignment length of 750 bp (Supplementary Data 3), from which a total of 163 unique haplotypes were evident (Supplementary Data 4). ...
Article
Full-text available
The whale shark (Rhincodon typus) is an iconic and endangered species with a broad distribution spanning warm-temperate and tropical oceans. Effective conservation management of the species requires an understanding of the degree of genetic connectivity among populations, which is hampered by the need for sampling that involves invasive techniques. Here, the feasibility of minimally-invasive sampling was explored by isolating and sequencing whale shark DNA from a commensal or possibly parasitic copepod, Pandarus rhincodonicus that occurs on the skin of the host. We successfully recovered mitochondrial control region DNA sequences (~1,000 bp) of the host via DNA extraction and polymerase chain reaction from whole copepod specimens. DNA sequences obtained from multiple copepods collected from the same shark exhibited 100% sequence similarity, suggesting a persistent association of copepods with individual hosts. Newly-generated mitochondrial haplotypes of whale shark hosts derived from the copepods were included in an analysis of the genetic structure of the global population of whale sharks (644 sequences; 136 haplotypes). Our results supported those of previous studies and suggested limited genetic structuring across most of the species range, but the presence of a genetically unique and potentially isolated population in the Atlantic Ocean. Furthermore, we recovered the mitogenome and nuclear ribosomal genes of a whale shark using a shotgun sequencing approach on copepod tissue. The recovered mitogenome is the third mitogenome reported for the species and the first from the Mozambique population. Our invertebrate DNA (iDNA) approach could be used to better understand the population structure of whale sharks, particularly in the Atlantic Ocean, and also for genetic analyses of other elasmobranchs parasitized by pandarid copepods.
... It is possible, given the relative ages of the two neonates and the time elapsed between their identification, that P-219 and P-272 were littermates. Recent genetic analysis of the Taiwanese whale shark embryos has shown that in a remaining subset of this litter all embryos were sired by the same male, suggesting that that the whole litter derived from a single sire (Schmidt et al 2010). Given the lack of evidence for long-term pairing in sharks, the staggered development of this full-sibling litter suggests that female whale sharks may store sperm for extended fertilization. ...
... Sibling status for P-219 and P-272 could have been demonstrated genetically, but legal restrictions on whale shark research prohibited obtaining tissue samples for genetic analysis. Claspers are present on embryonic whale sharks (Joung et al. 1996, Schmidt et al. 2010) allowing determination of sex. Although the sex of the P-219 animal was not recorded while in captivity, the presence of claspers on P-272 indicated it was a male (data not shown). ...
Article
Full-text available
The whale shark, Rhincodon typus, is a vulnerable species found in tropical waters worldwide. Young whale sharks are rarely seen, with only 12 encounters with neonatal animals reported in the scientific literature. During March 2009, two neonatal whale sharks were recovered alive near Donsol, Philippines, the first neonatal whale sharks identified in the western Pacific. The first animal measured 46 cm total length, and the second measured 64 cm total length, and both sharks carried the abdominal vitelline scars indicative of recent pupping. The 46 cm neonate is the smallest free-swimming whale shark ever recorded. Young of the year whale sharks between I and 2 m total length are also very rare. A previously unreported juvenile whale shark from the Philippines measuring 1.4 m total length is described here. These findings significantly add to the limited body of knowledge of whale sharks in their earliest free-swimming life stage.
... The whale shark (Rhincodon typus), which is listed as Vulnerable on the International Union for the Conservation of Nature's Red List (Norman 2005), is known to aggregate seasonally around areas of increased productivity (Colman 1997;Heyman et al. 2001;Nelson and Eckert 2007;Hobbs et al. 2009;Motta et al. 2010). While there is limited mixing of whale shark genetic material between ocean basins (Castro et al. 2007;Schmidt et al. 2010;Sequeira et al. 2013), the complete migratory routes taken by whale sharks have yet to be fully documented and remain relatively poorly understood (Rowat and Brooks 2012). ...
... In contrast, the movement of A-424 over ,2500 km is rare. It does, however, indicate the possibility of recruitment of whale sharks from Indonesian waters to Australia, which may account for limited genetic mixing between jurisdictions (see Castro et al. 2007;Schmidt et al. 2010;Sequeira et al. 2013). ...
Article
Whale sharks (Rhincodon typus) seasonally aggregate at Western Australia's Ningaloo Reef in the austral autumn and winter, but their occurrence beyond this region during spring and summer remains elusive. The aggregation at Ningaloo Reef coincides with a pulse of productivity following mass coral spawning in early autumn, with the population during this period dominated by juveniles that amass for feeding purposes. To investigate their movement patterns beyond Ningaloo Reef, whale sharks were fitted with SPOT (n≤13) or SPLASH (n≤1) tags between April and September (2010-14). Tagged whale sharks ranged in total length from 3 to 9m. Each whale shark was also photographed for its subsequent identification using Wildbook for Whale Sharks, and their years of residency at Ningaloo Reef determined. Temporal and spatial observations of whale shark sightings were also determined through the conducting of interviews with people throughout 14 coastal towns along the Western Australian coastline, as well as through historical sightings and the Wildbook database. Satellite tracking revealed that all sharks remained relatively close to the Western Australian coast, travelling a mean minimum distance of 1667 (±316, s.e.)km. Public reports, coupled with satellite tracking, demonstrated that whale sharks inhabit most of the Western Australian coast (from 35°S to 12°S), and that seasonal migrations beyond Ningaloo Reef may be to the north or south and may similarly be associated with areas of increased productivity. Journal compilation
... Sample sizes presented here are relatively small and further investigation is required to conclusively understand the relationship between adult size and breeding behaviours. However, a number of studies assessing multiple paternity in sharks (and elasmobranchs more widely) have tested five or less litters 1,13,40,42,55,56 and given the opportunistic nature and difficulties associated with sampling gravid elasmobranchs, the findings from this research provide valuable insight for these two species. ...
Article
Full-text available
This study assessed the presence and prevalence of multiple paternity (MP) in litters of grey reef sharks (Carcharhinus amblyrhynchos) and scalloped hammerheads (Sphyrna lewini) opportunistically caught in Papua New Guinea (PNG). Litter size between species were significantly different with an average of 3.3 pups for grey reef sharks and 17.2 pups for scalloped hammerhead. Using 14 and 10 microsatellite loci respectively, we identified MP in 66% of grey reef sharks (4 out of 6 litters) and 100% MP in scalloped hammerheads (5 litters). We found high paternal skew (the uneven contribution of sires per litter) and a positive correlation between female adult size and litter size in scalloped hammerheads but not in grey reef sharks. Differences in the frequency of MP between species and the identification of paternal skew may be linked with mating strategies and post-copulatory mechanisms. Multiple paternity is thought to benefit populations by enhancing genetic diversity therefore increasing the population’s genetic resilience to extrinsic pressures. The identification of MP in two shark species reported here, further elucidates the complex breeding strategies elasmobranchs undertake.
... Whale shark control region sequences from previous studies (Djibouti, Qatar, Mozambique, Seychelles, Maldives, Western Australia, Philippines, Taiwan, Japan, Mexican Pacific, Mexican Atlantic; Castro et al., 2007;Meekan et al., 2017;Ramírez-Macías et al., 2007;Schmidt et al., 2010;Sigsgaard et al., 2017;Vignaud et al., 2014;Yagishita et al., 2020) were incorporated into the alignment for subsequent analyses (Appendix S1: SI 3). ...
Article
Full-text available
The whale shark Rhincodon typus is found throughout the world's tropical and warm-temperate ocean basins. Despite their broad physical distribution, research on the species has been concentrated at a few aggregation sites. Comparing DNA sequences from sharks at different sites can provide a demographically neutral understanding of the whale shark's global ecology. Here, we created genetic profiles for 84 whale sharks from the Saudi Arabian Red Sea and 72 individuals from the coast of Tanzania using a combination of microsatellite and mitochondrial sequences. These two sites, separated by approximately 4500 km (shortest over-water distance), exhibit markedly different population demographics and behavioral ecologies. Eleven microsatellite DNA markers revealed that the two aggregation sites have similar levels of allelic richness and appear to be derived from the same source population. We sequenced the mitochondrial control region to produce multiple global haplotype networks (based on different alignment methodologies) that were broadly similar to each other in terms of population structure but suggested different demographic histories. Data from both microsatellite and mitochondrial markers demonstrated the stability of genetic diversity within the Saudi Arabian aggregation site throughout the sampling period. These results contrast previously measured declines in diversity at Ningaloo Reef, Western Australia. Mapping the geographic distribution of whale shark lineages provides insight into the species' connectivity and can be used to direct management efforts at both local and global scales. Similarly, understanding historical fluctuations in whale shark abundance provides a baseline by which to assess current trends. Continued development of new sequencing methods and the incorporation of genomic data could lead to considerable advances in the scientific understanding of whale shark population ecology and corresponding improvements to conservation policy.
... Meskipun teknologi penelitian terus berkembang, kehidupan Hiu Paus masih menjadi teka-teki. Hingga kini, t perkawinan dan reproduksi Hiu Paus masih belum banyak diketahui (Schmidt et al, 2010). Hiu Paus betina diduga dapat menyimpan sperma Hiu Paus jantan dan membuahi banyak telur dengan tetap menyimpan kantung telurnya sampai anak-anaknya menetas di dalam rahimnya. ...
... From previous studies, females were quite frequent with 17 individuals being sighted in Ningaloo water, Australia, an area which directly facing Indian Ocean (Sequeira et al 2013). On individual studies based on sex and age, it was still unknown whether whale sharks mate in pairs or in large groups (Schmidt et al 2010). ...
Article
Full-text available
The study was conducted to identify sex and size range composition of whale shark individuals from sightings and their appearance behavior in Cenderawasih Bay National Park, Indonesia. A total of 74 fishermen lift-nets ‘bagans’ in Sowa, Kwatisore, and Yaur areas from March to June 2013 were visited to document date, time, location, sex, size range, and number of whale sharks seen each day. Photographic identification was used as a non-invasive means to describe the population throughout the study period. Shark sizes were estimated using a diver body as reference length. A total of 134 whale sharks sightings was recorded within study areas. The highest frequency appearance of whale shark was within Sowa region with 76 sightings, followed by 51 sightings in Kwatisore region, and 7 sightings in Yaur region. From 37 whale sharks identified individual observed in Cenderawasih Bay, there were 36 individuals were identified as male and one as female with a size range of 3-7 meter, dominated by individual with size under 4 meter. From all the observed whale sharks, 44.44% were found not having any scars on their body, but some were having scars on their fins and mouth. Whale sharks in Cenderawasih Bay National Park can be seen moving around in water surface near the lift-net as their feeding behaviour. The fishermen activities might also have an impact on this behaviour, as the fishermen catching activities might drive whale sharks to move to the surface. The large percentage of juveniles recorded in this Cenderawasih Bay National Park population suggests that the area serves as an important habitat for young whale sharks.
... Evidence for multiple mating in elasmobranchs is accumulating, with polyandry (a mating pattern where females mate with more than one male per breeding season) apparently a common female mating strategy in sharks (Saville et al., 2002;Chapman et al., 2004;Feldheim et al., 2004;Daly-Engel et al., 2006Portnoy et al., 2007;Lage et al., 2008;Veríssimo et al., 2010b), rays and oviparous species (Chevolot et al., 2007). Multiple mating has been detected in all but two elasmobranchs studied to date: the Galapagos Shark, Carcharhinus galapagensis (Daly-Engel et al., 2006), and the Whale Shark, Rhincodon typus (Schmidt et al., 2010); however, these observations are based on single litters. The percentage of multiple male contributions to natural litters ranges from low in Squalid Sharks 11-17% of litters (Squalus mitsukurii, Daly-Engel et al., 2010;S. ...
... This study provides the first evidence of MP in G. galeus. With the exception of Carcharhinus galapagensis (Snodgrass & Heller 1905) (Daly-Engel et al., 2006), Carcharhinus melanopterus (Quoy & Gaimard 1824) (Mourier & Planes, 2013) and Rhincodon typus Smith 1828 (Schmidt et al., 2010), most parentage studies of elasmobranchs have reported evidence of MP (Fitzpatrick et al., 2012;Boomer et al., 2013). The studies of C. galapagensis and R. typus were only able to sample a single litter of seven and 29 embryos, respectively, which would have limited their ability to detect MP. ...
Article
This study assessed the levels of relatedness of Galeorhinus galeus of progeny arrays using six microsatellite DNA markers. A parentage analysis from five families (mother and litter) from the North Island of New Zealand suggested the occurrence of genetic polyandry in G. galeus with two of the five litters showing multiple sires involved in the progeny arrays. This finding may be consistent with the reproductive characteristics of G. galeus, in which females can potentially store sperm for long periods of time after the mating season.
... Second, a lag between a signal and the signaler's own division may have caused the gamete of a cell's deceased former occupant, or a cell's new occupant, to be used. The first case could only occur before any organism has divided in that cell (and so was restricted to early in a run); the second case of using a deceased organism's gamete is possible in a diverse array of sperm storing females in the animal kingdom, including many birds (Liem et al. 2001), insects (Klowden 2003), pigs (Suarez 2002), whale sharks (Schmidt et al. 2010), and snapping turtles (Galbraith et al. 1993). Thus, these cases, although biologically relevant, were fairly rare. ...
Article
Full-text available
Sexual signals are important in attracting and choosing mates; however, these signals and their associated preferences are often costly and frequently lost. Despite the prevalence of signaling system loss in many taxa, the factors leading to signal loss remain poorly understood. Here, we test the hypothesis that complexity in signal loss scenarios is due to the context-dependent nature of the many factors affecting signal loss itself. Using the Avida digital life platform , we evolved 50 replicates of ~250 lineages, each with a unique combination of parameters, including whether signaling is obligate or facultative; genetic linkage between signaling and receiving genes; population size; and strength of preference for signals. Each of these factors ostensibly plays a crucial role in signal loss, but was found to do so only under specific conditions. Under obligate signaling, genetic linkage, but not population size, influenced signal loss; under facultative signaling, genetic linkage does not have significant influence. Somewhat surprisingly, only a total loss of preference in the obligate signaling populations led to total signal loss, indicating that even a modest amount of preference is enough to maintain signaling systems. Strength of preference proved to be the strongest single force preventing signal loss, as it consistently overcame the potential effects of drift within our study. Our findings suggest that signaling loss is often dependent on not just preference for signals, population size, and genetic linkage, but also whether signals are required to initiate mating. These data provide an understanding of the factors (and their interactions) that may facilitate the maintenance of sexual signals.
... In sharks, direct observation of reproductive events such as mating behavior, including mate selection, is generally difficult, except for some tractable species that are small and accessible. Recent studies with a range of molecular techniques revealed the genetic mating system in lemon shark (Negaprion brevirostris, Feldheim et al. 2001a, b), hammerhead shark (Sphyrna tiburo, Chapman et al. 2004), bignose shark (Carcharhinus altimus, Daly-Engel et al. 2006), sandbar shark (Carcharhinus plumbeus, Daly-Engel et al. 2006, 2007, Portnoy et al. 2007), spiny dogfish (Lage et al. 2008Veríssimo et al. 2011), small-spotted catshark (Griffiths et al. 2012), nurse shark (Ginglymostoma cirratum, Saville et al. 2002, Heist et al. 2011 (Corrigan et al. 2015), starry smoothhound shark (Mustelus asterias, Farrell et al. 2014), and whale shark (Rhincodon typus, Schmidt et al. 2010). Genetic polyandry (i.e., multiple paternities in females) was detected in these studies, but the percentage of litters with multiple sires differs greatly among species from 11% in shortspine spurdog to 93% in brown smoothhound shark within the species for which more than two litters were investigated (Table 5.3). ...
Chapter
Sharks, which maintain the role of top predator in aquatic ecosystems, have a reproductive system and life history traits that are quite different from those of most teleosts, including internal fertilization, slow growth, high age at maturity, and the live birth of only a few well-formed offspring. Although shark species show diversity in many traits such as body size, morphology, diet, habitat (vertically, horizontally, and latitudinally), and reproductive system (ovoviviparous and viviparous), sexual difference in various phenotypic traits is one of their major characteristics. Sex-specific phenotypic traits such as life history parameters and sexual segregation are illustrated, focusing on shortfin mako and other species. A survey of the literature on growth suggests that slow growth and large body size in females are a major trend in sharks with significant intersexual difference in growth. Sexual segregation of sharks is reported with varying degrees of resolution, but its pattern is variable depending on the species, and the underlying mechanisms are largely unclear. The implication of intersexual difference in life history and behavioral traits is discussed from both evolutional and practical points of view. Existing studies that have evaluated the effect of sexual difference suggest the importance of including sex-specific traits in stock assessment and management, especially for species with marked sexual difference. Given its significance, both the study of sexual difference in the biological characteristics and the collection of sex-specific information on fishery statistics are important for understanding population dynamics and the sustainable exploitation of shark species.
... In species with diapause, however, the embryos typically implant en masse, and development ensues in a coordinated manner with embryos all being at the same developmental stage. (iii) Asynchronous parturition has been documented in the whale shark Rhincodon typus where embryos at different stages of development, ranging from pups still within egg cases to pups free swimming in the uterus, are present (Schmidt et al., 2010;up to 300 pups observed, Joung et al., 1996). (iv) The presence of embryos at different developmental stages can result from different times of fertilisation or sperm storage with ongoing fertilisation. ...
Article
Newly discovered pelvic and reproductive structures within placoderms, representing some of the most crownward members of the gnathostome stem group and the most basal jawed vertebrates, challenge established ideas on the origin of the pelvic girdle and reproductive complexity. Here we critically review previous descriptions of the pelvic structures in placoderms and reinterpret the morphology of the pelvic region within the arthrodires and ptyctodonts, in particular the position of the pelvic fin and the relationship of the male clasper to the pelvic girdle. Absence of clear articular surfaces on the clasper and girdle in the Arthrodira, along with evidence from the Ptyctodontida, suggest that these are separate structures along the body. We describe similarities between the pectoral and pelvic girdles and claspers, for example, all these have both dermal and perichondral (cartilaginous) components. Claspers in placoderms and chondrichthyans develop in very different ways; in sharks, claspers develop from the pelvic fin while the claspers in placoderms develop separately, suggesting that their independent development involved a posterior extension of the 'competent stripes' for fin development previously limited to the region between the paired pectoral and pelvic fins. Within this expanded zone, we suggest that clasper position relative to the pelvic fins was determined by genes responsible for limb position. Information on early gnathostome reproductive processes is preserved in both the Ptyctodontida and Arthrodira, including the presence of multiple embryos in pregnant females, embryos of differing sizes and of different sexes (e.g. male claspers preserved in some embyros). By comparison with chondrichthyans, these observations suggest more complex reproductive strategies in placoderms than previously appreciated.
... The developmental biology, breeding season, breeding places of this species remains unidentified. At present, 'critical' breeding habitats have yet to be defined, with only two locations, off India's (Whale Shark https://www.youtube.com/watch?v=yJz51i6Prmg), andTaiwan's coast(Schmidt et al. 2010), are the known places where new-born pups or pregnant sharks can be found.Turk.J. Fish.& Aquat. ...
Article
The ocean's largest extant elasmobranch fish whale shark (Rhincodon typus) has been wedged accidentally in gillnet by fishermen off the coast of Cuddalore, southeast coast of India. The paper also discusses conservative measures to protect the diversity of Whale shark.
... Carcharhinus altimus and C. galapagensis (Daly-Engel et al. 2006), Carcharhinus plumbeus (Daly-Engel et al. 2006, Portnoy et al. 2007, Squalus acanthias (Lage et al. 2008, , Veríssimo et al. 2011), Squalus mitsukurii (Daly-Engel et al. 2010, Rhincodon typus (Schmidt et al. 2010), Mustelus henlei (Byrne & Avise 2012), and Scyliorhinus canicula (Griffiths et al. 2012), and one skate species, Raja clavata (Chevolot et al. 2007). ...
Thesis
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The school shark (Galeorhinus galeus) is a coastal bentho-pelagic species that is highly migratory and has a widespread distribution in temperate waters. This species matures late, has a relatively low fecundity and is slow growing, which makes it vulnerable to overfishing. They are commercially fished throughout their distribution, and some global stocks have been under pressure because of poor management. In Australia, longline and gillnet fisheries targeted pregnant females and juveniles around Victorian and Tasmanian nursery grounds, resulting in loss of historical inshore nursery habitat. School shark tagging programmes have reported migration between Australian and New Zealand stocks, but preliminary genetic studies have suggested that there are slight genetic differences between the stocks. Currently, the Australian and New Zealand school shark fisheries are assessed and managed as separate stocks. However, the question of whether this species is comprised of a single population or multiple sub-populations in the South Pacific remains unresolved. Given the commercial importance of the school shark fisheries and the concern about stock levels on the regional and trans-Tasman scales, knowledge of stock structure is essential for effective management. The aim of this thesis research was to determine the levels of genetic diversity and population structure of G. galeus in New Zealand and Australia, and compare these to a population in Chile, using mitochondrial DNA (mtDNA) sequencing and microsatellite DNA markers. The DNA sequence of an 893 base pair region of the mtDNA control region (CR) was determined using 475 school shark samples and nine microsatellite DNA loci were genotyped in 239 individuals. Analyses of the data revealed strong evidence of genetic differentiation between G. galeus populations in Australasia and Chile, suggesting restricted gene flow among populations in the western and eastern areas of the Pacific Ocean. The FST values ranged from 0.188 to 0.300 for CR mtDNA, and 0.195 to 0.247 for microsatellite DNA in G. galeus. However, there was no evidence of stock differentiation among New Zealand/Australian sample sites for either mtDNA or microsatellite DNA data. These results support the model of a single panmictic stock across the Tasman Sea. The similarity of the results obtained from the maternally inherited mtDNA and biparental inherited microsatellite loci did not support the suggestion of sex-biased dispersal of G. galeus in the New i Zealand/Australia region and it was concluded that females and males had similar patterns of dispersal. Sharks can be either monogamous or polygamous, which is important when considering stock assessments and harvesting models. Multiple paternity has been reported in several shark species, however, the number of sires per litter varies considerably among species. An investigation of multiple paternity (MP) was conducted in G. galeus by assessing the levels of relatedness within progeny arrays using six polymorphic microsatellite DNA markers. Five “families” (mother and litters) were sampled from the North Island of New Zealand and a parentage analysis was conducted. The minimum number of males contributing to each progeny array was estimated by identifying the putative paternal alleles by allele counting and reconstructing multilocus genotypes method. The analysis showed the occurrence of genetic polyandry in G. galeus; two of five litters showing multiple sires involved in the progeny arrays (40%). The minimum number of sires per litter ranged from one to four. Although MP was only detected in two litters, this finding is consistent with the known reproductive characteristics of G. galeus. It can potentially store sperm for long periods of time and has a specific mating season when males and females typically mix on the edge of the continental shelf. Detecting MP within a litter has highlighted the importance of the post-copulatory selective processes in the G. galeus mating system, and this has implications for the management and conservation of genetic diversity.
... https://www.youtube.com/watch?v=yJz51i6Prmg), and Taiwan's coast (Schmidt et al. 2010), are the known places where new-born pups or pregnant sharks can be found. ...
Article
Full-text available
The ocean’s largest extant elasmobranch fish whale shark (Rhincodon typus) has been wedged accidentally in gillnet by fishermen off the coast of Cuddalore, southeast coast of India. The paper also discusses conservative measures to protect the diversity of Whale shark.
... Whale shark control region sequences from previous studies (Djibouti, Qatar, Mozambique, Seychelles, Maldives, Western Australia, Philippines, Taiwan, Japan, Mexican Pacific, Mexican Atlantic; Castro et al., 2007;Meekan et al., 2017;Ramírez-Macías et al., 2007;Schmidt et al., 2010;Sigsgaard et al., 2017;Vignaud et al., 2014;Yagishita et al., 2020) were incorporated into the alignment for subsequent analyses (Appendix S1: SI 3). ...
Conference Paper
Background A recent global study of whale shark population genetics has allowed for better understanding of genetic connections between aggregations in both the Indo-Pacific and Atlantic. This overview included an aggregation found within the Red Sea near Al Lith, Saudi Arabia, however the Mafia Island, Tanzania, aggregation was not part of the study. The ecological behavior of these aggregations differs with the Saudi Arabian individuals showing strong seasonality, while acoustic telemetry data revealed cryptic residency at Mafia Island. Approach Genetic analysis using 11 microsatellite markers was performed on whale sharks from both locations. A combination of primers sourced from previous studies and newly designed primers were used to compare both aggregations and the individuals within. The Red Sea population was compared between 5 seasons spanning 6 years from 2010–2015. The Tanzanian population was compared for 2 field seasons from 2012–2014. Temporal genetic diversity was examined using allelic richness on only the Saudi Arabian individuals due to a short sampling period in Tanzania. Kinship for both aggregations was tested using COLONY and KINALYZER. Results Over a 6 year period, genetic diversity in the Red Sea showed no significant change. Contrasting to other whale shark aggregations, allelic richness in the Red Sea shows no sign of reduction. Kinship analysis using COLONY found two potential sibling pairs in Tanzania. One pair had a high probability (.993) of being a full sibling dyad while the other had a lower probability (.357). There were no sibling pairs identified in the Red Sea. Conclusions The lack of significant change of genetic diversity in Al Lith, Saudi Arabia, differs from a trend at Ningaloo Reef, Australia that showed a decrease in genetic diversity. Although these differences could be driven by location, this should encourage further long term genetic sampling at aggregations to better understand whale shark population trends. The potential of sibling pairs being found within one aggregation warrants further investigation into kinship within and between aggregations throughout the Indo-Pacific.
... High intermixing of the Cenderawasih Bay whale shark by migration to and from other regions is thus the likely cause of the low level of gene diversity in the Bay. Inter-population migration resulting in gene-flow between regions was also inferred by (Schmidt et al. 2009(Schmidt et al. , 2010 based on the evidence from whole genome microsatellite data from whale sharkpopulations in the Indian, East Pacific and the Carribean regions. ...
Article
Full-text available
The whale shark (Rhincodon typus) inhabits Cenderawasih Bay at the Birdhead Seascape of Papua in high frequent sightings, but little is known about its genetic characteristics and connectivity. The study was conducted to characterize of the R. typus COI gene fragment from Cenderawasih Bay, in order to accurately compare with the 27 COI gene fragment sequences from the global whale shark deposited in the GenBank. A total of 28 meat samples of whale shark were collected by biopsy punch on a pole spear. The meat samples were extracted to obtain whole genome then amplified and sequenced to obtained COI nucleotides. The determined COI is a 669 bp, comprising of A = 26.5%, T/U = 30.5%, C = 28.3%, dan G = 14.7%. In total, 41 cutting sites of all the sequences ranged in size from 5-7 bp long. One COI single nucleotide polymorphisms and 2 haplotypes were identified. Single site substitution change from T to C for both haplotypes was observed. Overall, the haplotype diversity (Hd= 0.137) and nucleotide diversity (π=0.0002) were relatively low. A different nucleotide composition, number and arrangement of the sequences with the whale shark COI sequences from Cenderawasih Bay compared to COI gene fragment sequences from GenBank were observed. This study shows the availability of sequence of whale shark will contribute to aid further studies of molecular systematics, phylogeography, genetic differentiation, and conservation genetics.
... Gene flow between whale sharks inhabiting different ocean basins is limited (Castro et al. 2007;Schmidt et al. 2010;Sequeira et al. 2013); however, a comprehensive understanding of whale shark migratory routes and movement patterns globally has yet to be fully resolved (Rowat and Brooks 2012). Over recent decades, satellite tracking using the Argos system has become a popular means of studying the movement patterns of marine vertebrates (Hays et al. 2007). ...
Article
Whale sharks, Rhincodon typus, are found circumglobally in tropical and warm temperate seas, exhibiting a range of residency and movement patterns. To determine spatio-temporal habitat use by juvenile male whale sharks in Cenderawasih Bay, Indonesia, we collected data from June 2015 to November 2016 using 16 fin-mounted satellite tags that provided exceptionally long track durations. Fifteen tags transmitted for 48-534 days (mean = 321 ± 33, s.e.), with 13 tags transmitting for ≥220 days. Four sharks remained within the bay for the duration of the study, while of the 11 sharks that travelled outside the bay, eight left between March and May 2016. They ranged throughout coastal and offshore waters, travelling up to 5144 km away from Cenderawasih Bay, with a mean horizontal speed of only 3.3 km day-1 ± 0.70, s.e. A switching state space model was fitted to satellite fix data to identify behavioural states. It revealed that sharks spent an average of 81% of their time in foraging-related behaviours, mostly in shallow waters (median depth = 35 m), with travelling observed mainly over deeper waters (median depth = 1284 m). The movement patterns reveal variable periods of residency, with individual patterns of horizontal movement most likely in response to different abiotic and biotic factors, including food availability, which may trigger seasonal dispersal.
... Furthermore, this behavior may reduce the chances of sexual partner infertility or sperm depletion, thus increasing the reproductive fitness of females. Elasmobranchs present low genetic diversity due to their slow molecular evolution rates and k-selected life-history traits (Schmidt et al. 2010;Domingues et al. 2018). For this reason, MP may be essential in maintaining the genetic diversity within this group. ...
Article
Full-text available
Multiple paternity behavior (MP) has been recorded for seven elasmobranch orders. It remains unclear how this common behavior evolved and whether it occurs in all elasmobranchs or in certain lineages. Although MP may provide genetic benefits, elasmobranchs display an aggressive courtship behavior and females may become severely wounded, making multiple mating costly. Females can perform multiple matings to avoid excessive harassment in males (polyandry by convenience hypothesis). Studies challenge this hypothesis, suggesting that females are often able to avoid mating attempts by inappropriate males and copulate with several potential. In this study, an scientiometric analysis was performed concerning elasmobranch species presenting MP records, to reconstruct the evolutionary history of the complex sexual behavior in this group. The results indicate that MP behavior is widespread in the subclass, suggesting that it may have been originated in the common ancestor of elasmobranchs (plesiomorphic state). The data indicate a knowledge gap regarding the detection of MP in other elasmobranch orders and we suggest that investigative studies on the neglected elasmobranch and chimaera orders are required.
... Although multiple mating has previously been considered less common in pelagic species because mating encounters are probably rare in the open ocean, fertilizing multiple ova during any single mating event would maximize reproductive fitness (Gilmore 1993). With accumulating molecular evidence, pelagic sharks such as the tiger shark show no evidence of multiple paternity (Holmes et al. 2018), nor does the whale shark (Rhincodon typus) (Schmidt et al. 2010). On the other hand, the great white shark (Gubili 2008) and shortfin mako shark (Corrigan et al. 2015;present study) have been documented as using multiple paternity as a mating strategy. ...
Article
Full-text available
Multiple paternity has been demonstrated in a variety of sharks with different reproductive modes (i.e., viviparous, ovoviviparous, adelphophagy, oviparous), although the number of sires per litter varies considerably among species. To date, such analyses have focused mainly on coastal and nearshore shark species due to the difficulty in sampling oceanic sharks. In the present study, we observed multiple paternity in the oceanic shark Isurus oxyrinchus from seven polymorphic microsatellite loci and three litters collected from Nanfangao Fishing Port. Paternity tests showed that an average of 4.6 sires were assigned to each litter of I. oxyrinchus using COLONY software, and that the average number of sires dropped to 2.5 when using GERUD. These findings suggest that multiple paternity could be a common reproductive strategy used by the shortfin mako shark, and that this mating system should be integrated into a demographic model to make more accurate population projections and risk analyses in the future.
... where A max represents maximum age, A mat represents the age at maturity, R interval represents the reproductive interval or the number of years between litters (e.g., 1 for annual breeders, 2 for biennial breeders, etc.) and F represents fecundity. Species were excluded from our analysis of the relationship between LRO and relative sireship if litter paternity information was incomplete (whale shark Rhincodon typus Smith; Schmidt et al., 2010), basic life history data were not available (bluntnose sixgill shark Hexanchus griseus Bonnaterre; Larson et al., 2011) or mating along with pup birth occurred in an aquarium setting not reflecting natural conditions (spotted eagle ray Aetobatus narinari Euphrasén; Janse et al., 2013). ...
Article
Full-text available
Understanding mating systems is a pillar of behavioral ecology, placing the complex interactions between females and males into a reproductive context. The field of multiple paternity, the phenomenon whereby many sires contribute to an individual litter, has traditionally viewed females as passive players in a male‐male competitive framework. With the emergence of feminist perspectives in ecological fields, novel alternative mechanisms and evolutionary theories across invertebrate and vertebrate taxa recognize females are active stakeholders in the reproductive process. Despite their evolutionary significance, ecological diversity, and myriad reproductive modes elasmobranch (sharks, skates and rays) research lags behind other fields regarding complex biological processes, such as multiple paternity which is often ascribed to convenience polyandry. Here, we layout hypotheses and re‐synthesize multiple paternity literature from a female and life history perspective to highlight how alternative mechanisms influence the predominance of multiple paternity across elasmobranchs. We draw upon parallels in other invertebrate and vertebrate taxa to demonstrate how female elasmobranchs can influence multiple paternity outcomes that benefit their reproductive success. Our article challenges dogma that has resulted from years of dismissing the female perspective as important and provides a framework for future advancement using more holistic approaches to studying mating systems.
... High intermixing of the Cenderawasih Bay whale shark by migration to and from other regions is thus the likely cause of the low level of gene diversity in the Bay. Inter-population migration resulting in gene-flow between regions was also inferred by (Schmidt et al. 2009(Schmidt et al. , 2010 based on the evidence from whole genome microsatellite data from whale sharkpopulations in the Indian, East Pacific and the Carribean regions. ...
... Since then, Ningaloo Reef has been the site of the most targeted studies (Fig. 1), even if much research has been done elsewhere relating mainly to occurrence, movement, tourism, mortality and feeding behaviour ( Fig. 1; Table SI, Supporting Information). Few data are available on R. typus life-history traits such as reproduction (Joung et al ., 1996;Chang et al ., 1997;Schmidt et al ., 2010) and growth (Pauly, 1997;Wintner, 2000) or morphology and physiology (Wilson & Martin, 2001;Yopak & Frank, 2009;Dove et al ., 2010), which reflects the difficulty in obtaining specimens for detailed examination and measurement. From the summary of recent studies per site ( Fig. 1; Table SI, Supporting Information), the following trends emerge: (1) knowledge of R. typus ecology is most advanced in the Indian Ocean, and (2) similar work has been done in different locations worldwide, but (3) mostly at the scale of individual aggregations. ...
Article
Ten years have passed since the last synopsis of whale shark Rhincodon typus biogeography. While a recent review of the species' biology and ecology summarized the vast data collected since then, it is clear that information on population geographic connectivity, migration and demography of R. typus is still limited and scattered. Understanding R. typus migratory behaviour is central to its conservation management considering the genetic evidence suggesting local aggregations are connected at the generational scale over entire ocean basins. By collating available data on sightings, tracked movements and distribution information, this review provides evidence for the hypothesis of broad-scale connectivity among populations, and generates a model describing how the world's R. typus are part of a single, global meta-population. Rhincodon typus occurrence timings and distribution patterns make possible a connection between several aggregation sites in the Indian Ocean. The present conceptual model and validating data lend support to the hypothesis that R. typus are able to move among the three largest ocean basins with a minimum total travelling time of around 2-4 years. The model provides a worldwide perspective of possible R. typus migration routes, and suggests a modified focus for additional research to test its predictions. The framework can be used to trim the hypotheses for R. typus movements and aggregation timings, thereby isolating possible mating and breeding areas that are currently unknown. This will assist endeavours to predict the longer-term response of the species to ocean warming and changing patterns of human-induced mortality.
Article
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Although an understanding of mating systems is thought to be an important component of long-term pop-ulation management, these life history characteristics are poorly known in sharks. Here, we employ polymorphic microsatellite markers to test for the occurrence and preva-lence of multiple paternity in a population of the brown smoothhound shark, Mustelus henlei. We analyzed litters from 14 females sampled from the PaciWc coast of Baja California Sur. The minimum number of sires ranged from one to three with an average of 2.3 sires per litter. Regres-sion analyses did not indicate a relationship between female body size and number of sires, or female body size and size of the litter. A review of the existing literature on genetic mating systems in sharks suggests that polyandry may be common and that reproductive behavior may have evolved from conXicting selection pressures between the sexes.
Article
PURPOSE:: The purpose of this article was to describe persistent ostomy-specific concerns and adaptations in long-term (>5 years) colorectal cancer survivors with ostomies. SUBJECTS AND SETTINGS:: Thirty-three colorectal cancer survivors who participated in 8 gender- and health-related quality of life stratified focus groups and 130 colorectal cancer survivors who provided written comments to 2 open-ended questions on ostomy location and pouch problems participated in the study. Data were collected on health maintenance organization members in Oregon, southwestern Washington, and northern California. METHODS:: Qualitative data were analyzed for the 8 focus groups and written comments from 2 open-ended survey questions. Discussions from the focus groups were recorded, transcribed, and analyzed using content analysis. Written content from the open-ended questions was derived from a mailed questionnaire on health-related quality of life in survivors with ostomies and analyzed using content analysis. RESULTS:: Discussions related to persistent ostomy-related issues more than 5 years after formation were common. Persistent ostomy-related issues were focused on clothing restrictions and adaptations, dietary concerns, issues related to ostomy equipment and self-care, and the constant need to find solutions to adjust and readjust to living with an ostomy. CONCLUSIONS:: Ostomy-specific concerns persist 5 years and more for long-term colorectal cancer survivors after initial ostomy formation. Adaptations tend to be individualized and based on trial and error. Findings underscore the need to develop long-term support mechanisms that survivors can access to promote better coping and adjustment to living with an ostomy.
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This review highlights the potential role that post-copulatory sexual selection plays in elasmobranch reproductive systems and the utility of this group to further understanding of evolutionary responses to the post-copulatory processes of sperm competition and cryptic female choice. The growing genetic evidence for female multiple mating (polyandry) in elasmobranchs is summarized. While polyandry appears to be common in this group, rates of multiple paternity are highly variable between species suggesting that there is large variance in the strength of post-copulatory sexual selection among elasmobranchs. Possible adaptations of traits important for post-copulatory sexual selection are then considered. Particular emphasis is devoted to explore the potential for sperm competition and cryptic female choice to influence the evolution of testes size, sperm morphology, genital morphology and sperm storage organs. Finally, it is argued that future work should take advantage of the wealth of information on these reproductive traits already available in elasmobranchs to gain a better understanding of how post-copulatory sexual selection operates in this group.
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Conventional abdominoperineal excision for low rectal cancer has a higher local recurrence and reduced survival compared to anterior resection. An extralevator abdominoperineal excision (ELAPE) may improve outcome through removal of increased tissue in the distal rectum. Experience with ELAPE is limited and no studies have reported on quality of life (QOL) following this procedure. We describe a minimally invasive approach to ELAPE within an enhanced recovery programme, and present short-term results and QOL analyses. All laparoscopic ELAPEs were included in a prospective database. Demographics, intra-operative and post-operative outcomes were evaluated. Postoperative QOL was assessed using the European Organisation for Research and Treatment of Cancer (EORTC) questionnaires QLQ-C30 and QLQ-CR29. Thirteen laparoscopic ELAPEs were performed over a two-year period. All were enrolled in an enhanced recovery programme. The median age was 76. The median tumour height was 20 mm (range: 0-50 mm) from the dentate line and all patients received neoadjuvant treatment. The median duration of surgery was 300 minutes (range: 120-488 minutes), the mean blood loss was 150 ml and one procedure was converted to open surgery. There was no circumferential resection margin involvement or tumour perforation. The median duration of use of intravenous fluid, patient controlled analgesia and urinary catheterisation was 2, 2 and 2.5 days respectively and the median length of hospital stay was 7.5 days. Two patients developed perineal wound dehiscence. QOL analysis revealed high global health status (90.8), physical (91.3), emotional (98.3) and social functioning (100) scores, which compared favourably with EORTC reference values and published QOL scores following conventional abdominoperineal excision. Laparoscopic ELAPE within an enhanced recovery setting is a feasible and safe approach with acceptable short-term outcomes and post-operative quality of life.
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This report provides an overview of the con- servation status of chondrichthyans (sharks, rays, and chimaeras) in the Arabian Seas Region (ASR) and describes the results of a regional Red List workshop held in Abu Dhabi, United Arab Emirates, in February 2017. It identies those species that are threatened with extinction at the regional level, so that appropriate conservation action can be taken to improve their status. A regional overview of chondrichthyan fisheries, management and conservation is also presented. Although 184 species of sharks, rays, and chimaeras occur in the ASR, only the confirmed 153 species were considered in this project.The geographic scope encompasses the Red Sea, Gulf of Aden, Arabian Sea, Sea of Oman and the Gulf.This includes the Exclusive Economic Zone (EEZ) of 20 countries bordering three Large Marine Ecosystems (i.e., the Arabian Sea, Red Sea, and Somali Current). This region comprises some of the largest and most important chondrichthyan fishing nations in the world, including India and Pakistan. All assessments followed the IUCN Red List Categories and Criteria Version 3.1 and the Guidelines for Application of the IUCN Red List Criteria at Regional and National Levels Version 4.0. During the workshop, a network of leading international and regional experts on chondrichthyans and fisheries compiled data and knowledge to prepare 30 global (endemic species) and 123 regional species assessments. All assessments were agreed on by consensus at the workshop and any changes to statuses during the review process were agreed on through email correspondence with lead assessors and contributors prior to their submission to the IUCN Red List of Threatened Species and inclusion in this report.
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Purpose: Examination of reliability and validity of a specialized health-related quality of life questionnaire for rectal cancer (RC) survivors (≥5 years post-diagnosis). Methods: We mailed 1,063 Kaiser Permanente (KP) RC survivors (313 ostomy and 750 anastomosis) a questionnaire containing the Modified City of Hope Quality of Life-Ostomy (mCOH-QOL-O), SF-12v2, Duke-UNC Functional Social Support Questionnaire (FSSQ), and Memorial Sloan-Kettering Cancer Center Bowel Function Index (BFI). We adapted certain BFI items for use by subjects with intestinal ostomies. We evaluated reliability for all instruments with inter-item correlations and Cronbach's alpha. We assessed construct validity only for the BFI in the ostomy group, because such use has not been reported. Results: The overall response rate was 60.5 % (577 respondents/953 eligible). Compared with non-responders, participants were on average 2 years younger and more likely non-Hispanic white, resided in educationally non-deprived areas, and had KP membership through a group. The mCOH-QOL-O, SF-12, and FSSQ were found to be highly reliable for RC survivors. In the ostomy group, BFI Urgency/Soilage and Dietary subscales were found to be reliable, but Frequency was not. Factor analysis supported the construct of Urgency/Soilage and Dietary subscales in the ostomy group, although one item had a moderate correlation with all three factors. The BFI also demonstrated good concurrent validity with other instruments in the ostomy group. Conclusions: With possible exception of the BFI Frequency subscale in populations with ostomies, components of our survey can be used for the entire population of RC survivors, no matter whether they received anastomosis or ostomy.
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The present study was designed to assess the impact of neo-adjuvant chemoradiotherapy on the possibility of utilizing sphincter preserving techniques in rectal cancer surgery. For both patients and surgeons anal sphincter preserving surgery serves as the ideal procedure to treat rectal cancer. Patients with rectal cancer who were admitted to Shohadaye Tajrish hospital between 2001 and 2011 and underwent sphincter preserving or non-preserving surgery were identified. They were divided into those who had received neo-adjuvant chemo-radiotherapy prior to surgery and those who didn't, and the type of surgical procedure they underwent was compared between the two arms. Data regarding tumor pathology, tumor size and distance from anal verge before and after neo-adjuvant therapy, together with the duration of chemo-radiotherapy were also assessed. 103 patients with documented rectal cancer were included in our analysis. Among 47 patients who had not received neo-adjuvant therapy, 26 (55%) underwent APR while 15(32%) and 6(13%) patients were treated with LAR and VLAR respectively. Of the 56 patients who had gone through chemo-radiotherapy prior to surgery, 30 (53%) underwent APR while 14 (25%) and 10 (18%) patients were treated with LAR and VLAR respectively. 2 patients had unresectable tumor. Tumor staging before and after neo-adjuvant therapy showed a statistically significant difference (p=0.0001). Neo-adjuvant chemo-radiotherpy can decrease tumor size, increase the distance between the tumor and anal verge, and downgrade the staging. However, it does not necessarily increase the possibility of performing sphincter preserving surgery on patients suffering from low-lying tumors.
Article
Population genetics is essential for understanding and managing marine ecosystems, but sampling remains challenging. We demonstrate that high-throughput sequencing of seawater environmental DNA can provide useful estimates of genetic diversity in a whale shark (Rhincodon typus) aggregation. We recover similar mitochondrial haplotype frequencies in seawater compared to tissue samples, reliably placing the studied aggregation in a global genetic context and expanding the applications of environmental DNA to encompass population genetics of aquatic organisms.
Thesis
Los parámetros reproductivos de una población permiten evaluar su capacidad para sobreponerse ante la disminución de individuos, dichas evaluaciones han sido relevantes para la elaboración de planes de manejo en especies de importancia comercial. Aunado a esto, el sistema de apareamiento, juega un papel determinante en el éxito reproductivo de diversas especies. Actualmente los tiburones representan un grupo de importancia pesquera a nivel mundial, en la mayoría de las especies se ha reportado un apareamiento poliándrico, dando como resultado camadas fecundadas por múltiples machos (Paternidad Múltiple -PM-); sin embargo, una misma especie puede albergar individuos con apareamiento monógamo. Se desconoce cuáles son los factores que promueven una mayor o menor frecuencia de PM en especies que presentan ambos tipos de apareamiento. Estudios previos sugieren una relación entre el tamaño de las hembras y la PM, ya que las hembras grandes presentan camadas grandes. Esto lleva a hipotetizar que la PM está determinada por el tamaño de las hembras y sus camadas. Mustelus henlei es una especie que representa las principales capturas de elasmobranquios en la pesca artesanal del norte del Golfo de California, por lo que conocer los factores que determinan la PM resulta pertinente para la elaboración de planes de manejo que tomen en consideración dichas variables. El objetivo de este estudio fue evaluar la relación de la talla de las hembras y el tamaño de sus camadas con la PM en Mustelus henlei, mediante un análisis de paternidad con cuatro loci microsatelitales. Los resultados revelaron 56.52% de PM (n = 23 camadas), con un mínimo número de padres que osciló entre 1 y 4. En 10 de 13 camadas poliándricas se observó un sesgo en el éxito reproductivo de los machos, lo que sugiere la existencia de procesos post-copulatorios que determinan el porcentaje de paternidad individual. Un Modelo Linear Generalizado indicó que entre mayor es la talla de la hembra mayor es la probabilidad de ocurrencia de PM, lo que comprueba la hipótesis formulada en este estudio. Es probable que las hembras de menor tamaño tengan menos capacidades fisiológicas para mantener cópulas múltiples que las hembras grandes; este patrón, aunado a que las hembras no tienen periodos de descanso entre partos y suelen estar listas para ser fecundadas nuevamente, ha permitido que la especie mantenga altas tasas de crecimiento poblacional a lo largo de varias décadas y sus niveles de diversidad genética aún sean altos. Palabras clave: elasmobranquios, poliandria, paternidad múltiple, selección sexual.
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Buku ini merupakan edisi revisi dari buku “Hiu Paus Teluk Cenderawasih: Riset dan Monitoring berbasis Geografis, Biologis, Ekologis, Industri dan Prospektif Hiu Paus di Taman Nasional Teluk Cenderawasih” yang diterbitkan oleh Balai Besar Taman Nasional Teluk Cenderawasih (BBTNTC) pada tahun 2018.
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Preliminary observations of whale shark behavioural ecology are presented from St. Helena, a remote volcanic island in the South Atlantic. Whale shark sightings by fishers, government biologists and the general public have been recorded by the St. Helena Government since February 1999 and are presented here through to the end of 2014. A total of 328 sightings was collected on an ad hoc basis, a total of 931 animals, although the number of re-sightings within that total is not known. Increases in observations are likely coincident with increases in surveillance and public awareness of the presence of this species in the waters surrounding St Helena. On two occasions, small aggregations of whale sharks were observed at the bay at Jamestown; the animals were engaged in surface feeding behaviour similar to that seen in coastal aggregations in Mexico and Qatar. In contrast to other aggregations, however, animals observed at St Helena were numerically dominated by adult females, although mature males and some juveniles have also been observed. On two occasions, eyewitness accounts of mating behaviour were reported by two different reliable observers. These events took place in 2005 and 2007, both approximately 16 kilometers from shore, at different sites. They both involved belly-to-belly contact behaviour at the surface, in one case involving at least two males. This is the first report of putative mating behaviour in the whale shark. With the presence of both adult and juvenile animals, surface feeding aggregations, apparently pregnant females and the first observations of putative mating, the waters around St Helena are clearly an important multi-use habitat for whale sharks and are worthy of concerted conservation efforts.
Preprint
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Preliminary observations of whale shark behavioural ecology are presented from St. Helena, a remote volcanic island in the South Atlantic. Whale shark sightings by fishers, government biologists and the general public have been recorded by the St. Helena Government since February 1999 and are presented here through to the end of 2014. A total of 328 sightings was collected on an ad hoc basis, a total of 931 animals, although the number of re-sightings within that total is not known. Increases in observations are likely coincident with increases in surveillance and public awareness of the presence of this species in the waters surrounding St Helena. On two occasions, small aggregations of whale sharks were observed at the bay at Jamestown; the animals were engaged in surface feeding behaviour similar to that seen in coastal aggregations in Mexico and Qatar. In contrast to other aggregations, however, animals observed at St Helena were numerically dominated by adult females, although mature males and some juveniles have also been observed. On two occasions, eyewitness accounts of mating behaviour were reported by two different reliable observers. These events took place in 2005 and 2007, both approximately 16 kilometers from shore, at different sites. They both involved belly-to-belly contact behaviour at the surface, in one case involving at least two males. This is the first report of putative mating behaviour in the whale shark. With the presence of both adult and juvenile animals, surface feeding aggregations, apparently pregnant females and the first observations of putative mating, the waters around St Helena are clearly an important multi-use habitat for whale sharks and are worthy of concerted conservation efforts.
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To describe how gender shapes the concerns and adaptations of long-term (i.e., more than five years) colorectal cancer survivors with ostomies. Qualitative study using content analysis of focus group content. Oregon, southwestern Washington, and northern California. Four female and four male focus groups (N = 33) selected from 282 quantitative survey participants with health-related quality-of-life (HRQOL) scores in the highest or lowest quartile. Eight focus groups discussed the challenges of living with an ostomy. Content was recorded, transcribed, and analyzed using directive and summative content analysis. HRQOL domains of physical, psychological, social, and spiritual well-being. All groups reported avoiding foods that cause gas or rapid transit and discussed how limiting the amount of food eaten controlled the output. All groups discussed physical activities, getting support from friends and family, and the importance of being resilient. Both genders identified challenges with sexuality and intimacy. Coping and adjustment difficulties mostly were discussed by women, with men only discussing these issues to a small extent. Difficulties with sleep primarily were identified by women with low HRQOL. Problems with body image and depression were discussed only by women with low HRQOL. Common issues included diet management, physical activity, social support, and sexuality. Although both genders identified challenges, women described more specific psychological and social issues than men. Application of these gender-based differences can inform educational interventions for colorectal cancer survivors with ostomies.
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In the male blue shark Prionace glauca, paired testes produce spermatozoa year-round.
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For over a decade, we have been studying the reproductive behavior of the nurse shark, Ginglymostoma cirratum, in the Dry Torugas off the Florida Keys, an important mating and nursery ground for this species. In the course of these studies, we have used a variety of tags and tagging protocols to monitor individual animals. Here we report the use of molecular methods for the genetic analysis of nurse sharks. Specifically we have analyzed genetic variation at the MHC II alpha locus using the polymerase chain reaction (PCR) followed by restriction fragment length polymorphism (RFLP) analysis of the amplified products. We found this technique to be a relatively rapid and reliable method for identifying genetic differences between individual sharks. Applying this method to a family of sharks consisting of a mother and 32 pups, we demonstrate that at least four fathers must have fathered this brood. Multiple paternity in the nurse shark suggests a mechanism by which populations of this species may maximize genetic variability. This seems especially valuable for philopatric species whose migratory movement, and thus potential for genetic diversity, is limited.
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On 26 June 2006 an aggregation of 16 whale sharks was observed for a period of 4 hr in the north central Gulf of Mexico (GOM). The sharks remained within an area about 1.0 km 2 in size and continuously ram filter fed at the surface. Visual analysis of a plankton sample collected from the study site revealed the presence of copious amounts of fish eggs in mid-embryonic development and a minor amount of other zooplankton. A second plankton sample (control) collected about 3.5 km from the study site in an area where no whale sharks were pres-ent contained few eggs, however other zooplankton were similar to the study site sample in species composition and abundance. Two egg morphs were identified, and samples of one of the morphs, which represented 98% of the eggs at the study site, were verified by genetic analysis as little tunny, Euthynnus alleteratus. The observed feed-ing behavior and the abundance of fish eggs at the study site indicated the whale sharks were feeding on recently spawned little tunny eggs. This represents the first confirmed observation of a feeding aggregation of whale sharks in the GOM. RESUMEN El 26 de Junio del 2006 un agrupamiento de 16 tiburones ballena fue observado por un periodo de 4 horas en el centro norte del Golfo de Méjico (GOM). Los tiburones permanecieron dentro de un área alrededor de 1.0 km 2 y continuamente se desplazaron filtrando alimento en la superficie. Un análisis visual de una muestra de plankton colectada en el sitio de estudio revela la presencia de grandes cantidades de huevos de peces en un desar-rollo intermedio del embrión y una pequeña cantidad de otro zooplancton. En un área donde no habían tiburones ballena, una segunda muestra de plancton (control) colectada (alrededor de 3.5 km. del sitio de estudio) presento pocos huevos de peces, sin embargo el otro zooplancton fue similar en composición de especies y abundancia con la muestra colectada en el sitio de estudio. Dos formas de huevos fueron identificadas, la forma que represento el 98% de los huevos en el sitio de estudio fue identificada mediante un análisis genético como bacoreta, Euthynnus alletteratus. El comportamiento de alimentación observado y la abundancia de huevos de peces en el área de estudio indicaron que los tiburones ballena se alimentaron de un desove de huevos reciente de bacoreta. Esto representa la primera observación confirmada de una agregación de tiburones ballena en el GOM.
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Occurrence of whale sharks in India was considered a rarity until recently. Details of whale sharks that have landed so far in the Indian coasts are summarized. The whale shark has become a regular fishery in successive years off Gujarat coast for its meat, fins, liver, skin and cartilage. Over 1000 whale sharks have been hunted off Saurashtra coast during 1998. The present paper gives an account on the year-wise, season-wise, state-wise, depth-wise and gearwise distribution and occurrence of whale sharks, based on incidental landings and capture, in Indian coastal waters from 1889 to 1998. The threat to the whale shark due to commercial exploitation, its utilization and the need for conservation is discussed.
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Despite the importance of sharks to marine ecosystems as top predators and growing concern over the conservation status of many shark species, surprisingly little is known about many aspects of their reproduction patterns and life history. Better knowledge of breeding biology and reproductive parameters will be impor- tant for designing appropriate management plans to protect dwindling populations of sharks. Here, we report new information regarding the mating system and repro- ductive cycle of a large coastal shark, the lemon shark Negaprion brevirostris, revealed through field observations and genetic analyses of an adult female and her off- spring. Our findings demonstrate that this female exhibited philopatry to a nursery ground in Bimini, Bahamas, where she returned to give birth in both 1996 and 1998. Genetic analyses using DNA microsatellite loci developed for lemon sharks provided the first demonstration of polygamous mating and multiple paternity in a carchar- hinid shark; at least three males had sired the litter she delivered in 1998.
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Summary • The formulation of conservation policy relies heavily on demographic, biological and ecological knowledge that is often elusive for threatened species. Essential estimates of abundance, survival and life-history parameters are accessible through mark and recapture studies given a sufficiently large sample. Photographic identification of individuals is an established mark and recapture technique, but its full potential has rarely been exploited because of the unmanageable task of making visual identifications in large data sets. • We describe a novel technique for identifying individual whale sharks Rhincodon typus through numerical pattern matching of their natural surface ‘spot’ colourations. Together with scarring and other markers, spot patterns captured in photographs of whale shark flanks have been used, in the past, to make identifications by eye. We have automated this process by adapting a computer algorithm originally developed in astronomy for the comparison of star patterns in images of the night sky. • In tests using a set of previously identified shark images, our method correctly matched pairs exhibiting the same pattern in more than 90% of cases. From a larger library of previously unidentified images, it has to date produced more than 100 new matches. Our technique is robust in that the incidence of false positives is low, while failure to match images of the same shark is predominantly attributable to foreshortening in photographs obtained at oblique angles of more than 30°. • We describe our implementation of the pattern-matching algorithm, estimates of its efficacy, its incorporation into the new ECOCEAN Whale Shark Photo-identification Library, and prospects for its further refinement. We also comment on the biological and conservation implications of the capability of identifying individual sharks across wide geographical and temporal spans. • Synthesis and applications. An automated photo-identification technique has been developed that allows for efficient ‘virtual tagging’ of spotted animals. The pattern-matching software has been implemented within a Web-based library created for the management of generic encounter photographs and derived data. The combined capabilities have demonstrated the reliability of whale shark spot patterns for long-term identifications, and promise new ecological insights. Extension of the technique to other species is anticipated, with attendant benefits to management and conservation through improved understanding of life histories, population trends and migration routes, as well as ecological factors such as exploitation impact and the effectiveness of wildlife reserves. Journal of Applied Ecology (2005) doi: 10.1111/j.1365-2664.2005.01117.x
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In preparation for a study on population structure of the whale shark (Rhincodon typus), nine species-specific polymorphic microsatellite DNA markers were developed. An initial screening of 50 individuals from Holbox Island, Mexico found all nine loci to be polymorphic, with two to 17 alleles observed per locus. Observed and expected heterozygosity per locus ranged from 0.200 to 0.826 and from 0.213 to 0.857, respectively. Neither statistically significant deviations from Hardy–Weinberg expectations nor statistically significant linkage disequilibrium between loci were observed. These microsatellite loci appear suitable for examining population structure, kinship assessment and other applications.
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Proposed benefits of multiple paternity include increased reproductive output, elevated fitness of progeny, and maintenance of population genetic diversity. However, another consideration is whether multiple paternity is simply an unavoidable byproduct of sexual conflict, with males seeking to maximize mating encounters while females seek to minimize the stress of copulation. Here we examined the polyandrous mating system in sharks, with a focus on the reproductive genetics of the shortspine spurdog Squalus mitsukurii. Members of the genus Squalus are long-lived, slow-growing, and employ among the longest gestation periods of any vertebrate. To evaluate multiple paternity and genetic diversity in S. mitsukurii, we genotyped 27 litters plus 96 individuals with 8 microsatellite loci. Further, 670 bp of the mtDNA control region were sequenced in 112 individuals to examine population structure. S. mitsukurii in Hawaii showed low genetic diversity relative to other sharks (
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Elasmobranch mating systems have received growing attention in the past few years due to worldwide overexploitation of shark populations. Few studies to date have examined mating systems in sharks because of difficulty in sampling. The sandbar shark (Carcharhinus plumbeus) is heavily harvested around the world and is the dominant species in the main commercial fishery for large coastal sharks in the United States. In contrast, Hawaii hosts one of the few unexploited populations of sandbar sharks, and represents an opportunity to gather data on the reproductive biology of a vulnerable shark species without the confounding effects of fishing mortality. We examined the frequency of multiple paternity in Hawaiian sandbar sharks using 130 individuals (20 gravid females with 3-8 pups each per litter) surveyed with 6 polymorphic microsatellite loci, and determined that 8 of the 20 litters (40%) were multiply sired. A Bayesian approach estimated the frequency of multiple mating in this population at 43.8%, with a 95% confidence interval of 23-63%. We conclude that multiple paternity and genetic monogamy occur with roughly equal frequency in the Hawaiian sandbar shark population. This study may serve as groundwork for understanding the impact of commercial fishing pressure on elasmobranch mating systems.
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This study confirms reports by fishermen of a large and predictable aggregation of whale sharks Rhincodon typus along the Belize Barrier Reef. Although whale sharks are rarely sighted at this location during most of the year, we counted as many as 25 whale sharks in a 50 m diameter area on 1 occasion and tagged 6 sharks during a 22 min period on another. The whale shark aggregation coincides seasonally and temporally with a multispecies reef-fish spawning aggregation at a reef promontory, Gladden Spit, at sunset, during the full and last- quarter moon periods of April and May each year. We report here, for the first time, that whale sharks feed on the freshly released spawn of cubera snappers Lutjanus cyanopterus and dog snappers L, jocu (Lutjanidae), and have documented the phenomenon with still and digital video photography of hundreds of feeding events. There is consensus locally that this remarkable interaction is in need of immediate protection from overfishing of snappers and unregulated tourism development. Our continued investigations are providing management recommendations for a new marine reserve at the site.
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The finding of neonatal whale sharks from Northern Indian Ocean waters off of Pakistan and Bangladesh and the description of several very small whale sharks from around Seychelles during the last few years are reported. These findings are discussed in relation to published reports of growth rates, the areas of occurrence and segregation by sex, and the behaviour of very young whale sharks, which are key factors in their conservation management.
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The tiger shark (Galeocerdo cuvier) is the largest shark in the family Carcharhinidae and the only carcharhinid with aplacental viviparous (ovoviviparous) reproduction. Despite its size and prevalence, many details of tiger shark reproductive biology are unknown. Size at maturity and litter size have been reported by several authors, but a lack of large numbers of pregnant females has made it difficult to determine gestation period, seasonality, and timing of the female reproductive cycle. Here we analyze data from shark control program fishing and incidental catches in Hawaii (n=318) to construct the most complete picture of tiger shark reproduction to date. Males reached maturity at approximately 292cm total length (TL) based on clasper calcification, whereas females matured between 330 and 345cm TL based on oviducal gland and uterus widths. Litter sizes ranged from 3 to 57 with a mean of 32.6 embryos per litter. Data from 23 litters from various months of the year indicate that tiger sharks are usually 80–90cm TL at birth, and that the gestation period is 15–16 months. Mating scars were observed in January–February and sperm is presumably stored for 4–5months until ovulation takes place in May–July. Gestation begins in June–July and pups are born in September–October of the following year. Our data suggest that female tiger sharks in Hawaii give birth only once every three years. This could have major implications for conservation and management of this species, as it suggests that tiger shark fecundity is 33% lower than previously thought. This could greatly reduce the ability of this species to rebound from fishing pressure.
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We tested for presence or absence of multiple paternity in single litters from each of three congeneric shark species in Hawaii: the sandbar shark, Carcharhinus plumbeus, bignose shark, Carcharhinus altimus, and Galapagos shark, Carcharhinus galapagensis. Based on eight polymorphic microsatellite loci, we excluded paternity by a single sire in sandbar and bignose sharks, but could not exclude a single sire for the litter from the Galapagos shark. This study doubles the number of shark species tested for multiple paternity, and is the first demonstration of multiple paternity in sandbar and bignose sharks.
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The maternal–embryo relationship was determined for the piked spurdog (Squalus megalops). In addition, the increase in offspring size with maternal size was studied and the embryonic development was described. Wet weight of in utero eggs and offspring size was correlated with maternal size; larger females produced larger embryos which would have higher survival rate and reproductive value. All embryos present in a female were at a similar stage of development. The external yolk sac is reabsorbed late in gestation, suggesting that embryos are mostly nourished by yolk sac reserves. Embryo size-at-birth varied considerably (180–244mm total length) as a result of the significant variability in ova size at ovulation. The amounts of water, organic and inorganic matter of embryos at different stages of development were measured to determine possible maternal contributions during embryonic development. Total wet weight from smallest and largest in utero eggs to smallest and largest term embryos changed by +46 and +58%, respectively. This pattern was due to a change in water content by +137 and +154%, and inorganic matter by +100 and +156%. Organic matter of smallest and largest in utero eggs changed by −23 and −17%, respectively. The uterus of pregnant females became specialised for water and mineral transport, not nutrient provision. These results indicate that S. megalops is a strict yolk-sac viviparous species with no maternal contribution of organic matter during development.
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The presence of whale sharks (Rhincodon typus) in Bahía de Los Angeles, Baja California Norte, Mexico, is a seasonal phenomenon, occurring during the months of June–November, with highest abundance from August to October. The foraging ecology of whale sharks in Bahía de Los Angeles was studied from 28 July to 26 October 1999. During this period, 19 individual whale sharks were identified, including nine males, three females, and seven whose sex was not identified. Feeding by whale sharks was observed on 132 out of 190 sightings. Approximately 80% of the feeding events occurred in areas with ≤10 m bottom depth (mean ± S.D. = 7.0 ± 5.5 m), and were concentrated primarily in the southernmost region of the bay. The highest numbers of feeding events occurred between 12.00 and 16.00 h. Mean (±S.D.) sea surface temperature during these events was 29.7 ± 1.1 °C. Three feeding behaviors, “active”, “vertical”, and “passive”, and one non-feeding behavior, “cruising”, were characterized. Analysis of plankton samples collected beside feeding sharks revealed that zooplankton, primarily copepods (∼85% of total zooplankton abundance) appeared to be the primary prey source in the bay. Although whale sharks were observed feeding among large schools of baitfish (sardines, anchovies), whale sharks were never observed directly preying upon these fish. Whale sharks may target baitfish to locate zooplankton, as these fish can be indicators of plankton rich patches. Zooplankton abundance was significantly different among the three feeding behaviors, suggesting that prey abundance may influence which feeding technique was utilized. Feeding was not observed when the minimum density of zooplankton was less than ∼10.0 × 103 individuals m−3. Whale sharks may be following oceanographic cues (physical and biological) both within the bay as well as throughout the Gulf of California that are favorable for increases of prey resources. Because whale shark ecotourism is rapidly increasing in Bahía de Los Angeles, it is important to identify and manage ecologically important areas utilized by whale sharks within the bay to ensure the continued integrity of the habitat that supports whale shark presence.
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There is growing interest in the mating systems of sharks and their relatives (Class Chondrichthyes) because these ancient fishes occupy a key position in vertebrate phylogeny and are increasingly in need of conservation due to widespread overexploitation. Based on precious few genetic and field observational studies, current speculation is that polyandrous mating strategies and multiple paternity may be common in sharks as they are in most other vertebrates. Here, we test this hypothesis by examining the genetic mating system of the bonnethead shark, Sphyrna tiburo, using microsatellite DNA profiling of 22 litters (22 mothers, 188 embryos genotyped at four polymorphic loci) obtained from multiple locations along the west coast of Florida. Contrary to expectations based on the ability of female S. tiburo to store sperm, the social nature of this species and the 100% multiple paternity observed in two other coastal shark species, over 81% of sampled bonnethead females produced litters sired by a single male (i.e. genetic monogamy). When multiple paternity occurred in S. tiburo, there was an indication of increased incidence in larger mothers with bigger litters. Our data suggest that sharks may exhibit complex genetic mating systems with a high degree of interspecific variability, and as a result some species may be more susceptible to loss of genetic variation in the face of escalating fishing pressure. Based on these findings, we suggest that knowledge of elasmobranch mating systems should be an important component of conservation and management programmes for these heavily exploited species.
Article
From February 1990 to July 1992, the reproduction of the blue shark, Prionace glauca, in the south-western equatorial Atlantic Ocean was studied. During this period, 88 females and 82 males were examined. Females were found in 4 different sexual stages: preovulatory (22), pregnant (47), postovulatory (non-pregnant) (7), and subadult (12). Their fork length ranged from 162 to 225 cm. Half of the females were in early pregnancy. Embryos in completely different stages of development were found in 4 of them. Oviducal glands of 44 females were examined and in 38 spermatozoa were found. These results indicate that ovulation and fertilization took place from December to July. Most of the males were adult and only 14 specimens seemed to be sexually immature. Many adult males were lacking sperm packs and had a very low volume of seminal fluid, suggesting that they were probably sexually resting. Their fork length ranged from 156 to 228 cm. © 1994, The Japanese Society of Fisheries Science. All rights reserved.
Article
We analysed video records of three mating events involving nine free-living whitetip reef sharks in Cocos Islands, Costa Rica to examine reproductive behaviour in this species. We describe several behaviours never before documented in this species, and four behaviours never before documented in any elasmobranch. Here, we also present the first hypothesis for the function of the male's paired reproductive organs, the siphon sacs, to be based on observations of mating sharks. We introduce terminology for three separate siphon sac structural components that are externally visible during courtship and mating in this species. Based on our analyses, as well as evidence from past mating studies, the siphon sacs in whitetip reef sharks appear to be used to propel sperm into the female's reproductive tract, not for flushing the female's reproductive tract of sperm from previous males. We discuss the implications of 'group courtship', 'siphon isthmus constriction', 'reverse thrusting', 'postrelease gaping' and 'noncopulatory ejaculation'.
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DNA was purified from whale shark Rhincodon typus faecal material that contained DNA derived from their prey. A DNA‐based krill identification method was used to determine the exact krill species upon which the whale shark was feeding, where morphological analysis had failed to make an identification.
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Dasyatis sayi is a common year-round resident in the brackish Indian River lagoon system on the central east coast of Florida. We studied the species in the Cape Canaveral area from July 1975 to January 1978. Catch-per-unit-effort generally peaked in the spring and fall, was depressed in winter, and usually was significantly higher at night than during the day. Catch rates were always highest in Mosquito Lagoon, the most saline section of the study area. Females reached a size of 73 cm DW and 21 kg; males reached 52 cm and 7 kg. Females matured between 50-54 cm DW and males between 30-36 cm. The reproductive cycle was significantly different from that of the sympatric D. sabina. Ovarian egg size and male gonasomatic index both peaked in May, indicating that mating occurred in spring. Uterine eggs were present from June through the following March but no embryonic development was evident. Fetal development began in early April and parturition occurred in middle to late May, followed immediately by ovulation. There were 1-6 young per brood and neonates were 15-17 cm DW at birth.
Article
Reproduction and early embryo development of Rhizoprionodon taylori from Cleveland Bay, Queensland, was studied on the basis of 455 specimens caught between May 1987 and February 1990. Males and females mature at sizes larger than those reported from northern Western Australia, the Northern Territory and far northern Queensland. Mating occurs annually in summer, and the gestation period is approximately 11.5 months. After development to a small blastodermic disc, the embryos enter a state of diapause that lasts approximately 7 months. R. taylori is the only species of shark that is known to have a period of embryonic diapause. The litter size ranges from 1 to 10 (mean 4.9, being markedly larger than that for other carcharhinid species of a similar size. The size at birth is 220- 260 mm. The reproductive and developmental traits are discussed in relation to the life histories of this species and other carcharhinids.
Article
In total, 491 whitespotted bamboo sharks were collected from northern Taiwanese waters from February 2002 to February 2003. The sex ratio of the specimens was 0.65, total length (TL) ranged from 35.3–85 cm, and weight ranged 124–2580 g. The mean size at first maturity was estimated to be 64.9 and 65.6 cm TL for females and males, respectively, based on the relationship between mature percentage and TL. The ovulation season was estimated as March to May based on gonadosomatic index (GSI) variations and captive observation. The monthly changes in GSI of males suggested that the mating season was from December to January. The inconsistency between mating and ovulation seasons suggested that females have sperm storage and delayed fertilization. One or two eggs were deposited every 6 or 7 days on average. Deposition of eggs extended for 2 months, and fecundity was 8 ± 3.8 eggs. Thirteen of 48 eggs deposited in 2003 were hatched and the hatching rate was 0.27. The hatching period was 107 ± 9.3 days with accumulated water temperature ranging from 2372–2835°C.
Article
Seven juvenile whale sharks ranging from 550 to 930 mm in length are reported. Measurements of six are tabulated with remeasurements of the single known embryo. The mode of reproduction of this shark is again questioned, and the lack of records of sizes between 1 and almost 4 m is discussed.
Article
Elasmobranch fishes utilize a variety of means to provide nourishment for their developing young. All employ internal fertilization and sperm storage within the female genital tract. Some elasmobranchs, including all the skates and some sharks, are oviparous. In these species, fertilized eggs are enclosed in a tough egg case that is secreted by the nidamental or shell gland. The female lays the egg cases and development is entirely dependent on the yolk stores sequestered in the yolk sac. Upon oviposition, the embryo weighs less than the fertilized egg. The majority of elasmobranchs are viviparous, however, and utilize a variety of strategies to provide nourishment and satisfy respiratory demands of the developing young. Some sharks simply retain their young in the dilated posterior segment of the oviduct. In its simplest form, the maternal uterus does not provide any additional nutrients to the embryos. Other elasmobranchs develop secretory uterine villi that produce nutrient histotroph to supplement oocyte yolk stores. Uterine secretions find their zenith in the stingrays. Following yolk depletion, the uterine lining hypertrophies into secretory appendages termed trophonemata. The process by which the uterine secretions, also known as uterine milk or histotroph, are elaborated resembles the production of breast milk in higher vertebrates, and the milk is rich in protein and lipid. Concurrent with growth of the embryos, the vascular bed of the trophonemata enlarges to form sinusoids that project out to the surface to form a functional respiratory membrane. In lamnoid sharks, following yolk use, the embryos develop precocious dentition and feed on intrauterine eggs and siblings. There is generally one fetus per uterus and it grows to enormous proportions of up to 4 feet in length. In placental sharks the yolk sac is not withdrawn to become incorporated into the abdominal wall. Instead, it lengthens to form an umbilical cord and the yolk sac becomes modified into a functional epitheliochorial placenta. © 1993 Wiley-Liss, Inc.
Article
An understanding of alternative mating systems is a fundamental requirement for the effective management of vulnerable species. Microsatellite analysis of spiny dogfish Squalus acanthias broods from the north-west Atlantic provides novel evidence of polyandry in this species.
Article
A single-sex model is presented that calculates the probability of detecting multiple mating (PrDM) given genetic data from the single genetic parent and a sample of its offspring. The model incorporates the effects of numbers of loci, alleles, offspring and genetic parents contributing to the multiple mating, all of which effect PrDM. The model is used to determine the actual number of loci and offspring that are required to detect multiply mated broods with high probability (80 and 95%). For example, if two sires contribute with equal fertilization success to multiply mated broods, then only 10 offspring and one locus with seven equally common alleles are required to ensure that 80% of multiple mated broods are detected. Ninety-five per cent of multiple mated broods can be detected with 10 offspring and five loci with four equally common alleles. The utility of the model is demonstrated with biological examples addressing geographic variation in multiple paternity among natural populations of guppies Poecilia reticulata and mosquitofish Gambusia holbrooki.
Article
Spermatozoa stored in oviducal glands of sharks sampled off the North American east coast were revealed by viewing stained tissue sections using light microscopy. Of eleven species surveyed, sperm were found in nine:Alopias vulpinus, Lamna nasus, Carcharhinus obscurus, Carcharhinus plumbeus, Galeocerdo cuvieri, Prionace glauca, Rhizoprionodon terraenovae, Sphyrna lewini andSphyrna tiburo. Three insemination patterns are proposed to account for differences noted in these findings: (1) non-storage/immediate insemination for sharks such asLamna nasus; (2) short-term storage/delayed insemination as found in sharks in which ovulation is prolonged over weeks or months such asRhizoprionodon terraenovae, and (3) long-term storage/repeated insemination, a characteristic of nomadic sharks such asPrionace glauca andCarcharhinus obscurus which can store sperm in specialized tubules for months to years.
Article
This study demonstrates that the females and males of two species of ray (Trygonoptera personata and T. mucosa) attain between ~33 and ~49% of their asymptotic sizes by the time of parturition, and that their growth throughout the whole period of pre- and postnatal growth can be described well by a single and smooth growth curve. The individuals used for this study were caught at regular intervals by trawling along the lower west coast of Australia. Conception takes place at a similar time in both Trygonoptera species (i.e. between late autumn and mid-winter), and parturition occurs 10–12 months later. The eggs found in the left uterus of female T. personata were enclosed in a membranous egg case and remained in embryonic diapause for ~5 months between mid-winter and late spring, which is the first recorded instance of such diapause in a urolophid. Embryonic diapause in T. personata was followed by a period of particularly rapid embryonic development, during which the mean disc width increased from 11 mm in December to 113 mm in April, when parturition occurred. Although no females of T. mucosa were caught with either eggs or embryos in certain months, the data still showed that their eggs are enclosed in a case and that their embryos grow less rapidly than those of T. personata. Trygonoptera mucosa attained greater maximum disc widths than T. personata both in females (369 vs 311 mm) and males (283 vs 269 mm). The maximum ages attained, after parturition, by the females of T. personata (16 years) and T. mucosa (17 years) were greater than those of their males (10 and 12 years, respectively). Maturity is typically attained by the females of T. personata and T. mucosa at ~230 and 250 mm, respectively, and by the males of both species at ~220 mm. Maturity was reached by at least 50% of the females of T. personata and T. mucosa by the end of their fourth and fifth years of life after parturition, respectively, and by >50% of the males of these two species by the completion of their fourth and second years of life after parturition, respectively. The von Bertalanffy and Schnute growth equations for the females and males of both species provided a good fit for the disc widths-at-age of postnatal fish, with r 2 values for these equations ranging from 0.874 to 0.938. Although the von Bertalanffy growth curve also provided a good fit for the disc widths-at-age of both sexes of both species throughout much of the total growth period (i.e. including embryonic growth), it did not accommodate well the disc widths-at-age of the oldest and largest fish. This latter deficiency was entirely or largely eliminated by the use of the Schnute growth equation (r 2 values ranged from 0.919 to 0.938), which incorporates four rather than three parameters as in the von Bertalanffy growth equation.
Article
A total of 23 whale sharks were identified over a 5d period in the Arta Bay region of the Gulf of Tadjora, Djibouti. Most of the sharks aggregating in this area were small (<4m TL) males. Individuals were identified using photographs of distinctive scars and spot and stripe patterns on the sides of the animals. Of these, 65% had scarring that was attributable to boat or propeller strikes. Most of the whale sharks we encountered were feeding on dense accumulations of plankton in shallow water just off (10–200m) the shoreline. This food source may account for the aggregation of sharks in this area. One 3m male shark was tagged with an ARGOS (Splash) satellite tag for 9d. During this time the shark traversed to the shoreline on the opposite side of the Gulf (a distance of 14km) and then returned to the Arta Bay area before retracing his path to the other shore. The shark spent most of the daylight hours at the surface, while at night dives were more frequent, deeper and for longer durations.
Article
Little information on the movements and use of habitat by whale sharks is available. We present data on regional horizontal and local vertical movement of juvenile whale shark from waters off Seychelles into the Indian Ocean, as recorded by satellite telemetry. Tracking data show that the direction of travel in three sharks was influenced by the prevailing geo-strophic currents. The temperature distribution frequencies recorded show that the sharks spent the majority of time in waters of 25–35 °C. However, short exposures to very cold waters, below 10 °C were recorded and these are consistent with dives to deeper depths. Depth recordings show that up to 53% of the time was spent in water shallower than 10 m, but dives to depths of 750–1000 m were also recorded. These results are discussed in relation to diel patterns and diving behaviour in a similar planktivore, the basking shark. The marked preference of the whale sharks for swimming in relatively shallow water may indicate the importance of this range with respect to their foraging activities and has implications for their management and conservation.
Article
A highly variable fragment of the mtDNA control region of the whale shark was sequenced to investigate genetic population structure at three localities in the Gulf of California. We found high levels of variation with 14 haplotypes among 36 individuals (h = 0.90, π = 0.005). AMOVA analysis did not detect significant structuring among Gulf of California whale sharks (P > 0.12, ΦST 0.029), which indicates a single, highly mobile population. Genetic analysis, along with field observations, suggests natal philopatry of female whale sharks in the Gulf of California.
Article
Behavioural ecology of whale sharks is very incompletely known. Recent rapid development of whale shark-based ecotourism at several widespread localities risks deleterious impacts on the behaviour, habitat, and ecology of the target species. Available information on behavioural ecology of whale sharks is synthesised from the published literature (including inferences from related species) and personal observations. This information is reviewed within the unifying framework of theoretical behavioural ecology, revealing opportunities to fill in critical knowledge gaps. Topics covered include: sensory biology, movements, anti-predator behaviour, feeding behaviour, social behaviour, reproductive behaviour and interactions with humans. Data collected by whale shark ecotourists and operators could help fill in some of the knowledge gaps about the behavioural ecology of this species.
Article
Whale sharks are known to occur in Malagasy waters although very little research has been completed to further document the species. In order to increase the current national knowledge of the species, it is planned to conduct whale shark surveys in Madagascar. An initial investigation based on interviews of local fishers and dive operators was completed to establish the logistical baseline for such surveys. It was found that whale sharks are present around the majority of the Madagascar coastline but most known sightings have occurred along the north-western coast. In Nosy Be, it appears whale sharks occur all year round, particularly during planktonic blooms. Plans for further assessment involving a combination of boat based observations, photo identification, and acoustic and satellite tagging are described.
Article
A software suite KINALYZER reconstructs full-sibling groups without parental information using data from codominant marker loci such as microsatellites. KINALYZER utilizes a new algorithm for sibling reconstruction in diploid organisms based on combinatorial optimization. KINALYZER makes use of a Minimum 2-Allele Set Cover approach based on Mendelian inheritance rules and finds the smallest number of sibling groups that contain all the individuals in the sample. Also available is a 'Greedy Consensus' approach that reconstructs sibgroups using subsets of loci and finds the consensus of the partial solutions. Unlike likelihood methods for sibling reconstruction, KINALYZER does not require information about population allele frequencies and it makes no assumptions regarding the mating system of the species. KINALYZER is freely available as a web-based service.
Article
The studies on patient-reported symptoms and quality of life following the treatment of rectal cancer were evaluated; guidelines for future quality of life studies in this field are proposed. Relevant papers in the English language were identified via Medline from January 1970 to November 1997, supplemented by a manual search for similar articles. Patients suffer various short- and long-term complications after treatment of rectal cancer, although the reported prevalence of such problems varies from study to study. Recent prospective studies have shown that, despite these problems, global quality of life scores as measured by generic questionnaires improve after surgery. The methodological shortcomings of previous work must be rectified if quality of life studies are to have relevance in patient management.
Article
Little is known of how the quality of life of patients with rectal cancer changes after surgery, and whether or not quality of life is associated with and predictive of survival. The aims of this study were to address these issues. The Medical Outcomes Study Short Form 36 (SF-36), and the European Organization for the Research and Treatment of Cancer QLQ-C30 and QLQ-CR38 quality of life questionnaires were administered to patients before surgery for rectal cancer, on discharge home and at 3-month intervals after operation for up to 1 year. Survival was measured in days from the time of surgery to death. Sixty-five patients with a median age of 67 years participated. Most quality of life scores dropped significantly below baseline in the early postoperative period. From the third month onwards some scores, such as the global quality of life score and emotional function score on the QLQ-C30, improved. Other scores, including role function, fatigue and pain on the QLQ-C30, were similar to baseline values after 3-6 months and remained unchanged. However, scores such as sexual enjoyment and male sexual problems on the QLQ-CR38 were worse than baseline in the early postoperative period and remained poor thereafter. Stepwise regres