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Quantitative analysis of production traits in saltwater crocodiles (Crocodylus porosus): IV. Number of scale rows
Abstract
A total of 3156 scale row records, comprising 1739 full-sibling records from 30 families from Janamba Croc Farm (NT, Australia) and 1417 parent-offspring records from 19 families from Wildlife Management International, Pty Ltd (NT, Australia), collected at each facility using a different method, were analysed using ASReml. The full-sibling heritability estimate for the Janamba data was 0.37 (SE 0.03). The animal model estimate of heritability for the Wildlife Management International (WMI) data, also based predominantly on full-sibling data, was 0.42 (SE 0.04). The counts from three counting methods were evaluated by regression analysis on 100 individuals and were found to be highly correlated. Using the regression relationship, the WMI data were transformed and pooled with the Janamba data to give an animal model heritability estimate of 0.42 (SE 0.04). A multitrait analysis revealed negligible correlations (both phenotypical and genetical) between hatchling size traits and the number of scale rows. There is ample genetic variation to incorporate this trait into a genetic improvement programme for farmed saltwater crocodiles.
... CrocPLAN (Isberg et al., 2004) was the first multi-trait genetic improvement program developed for a crocodilian. Saltwater crocodile (Crocodylus porosus) production records from Janamba Crocodile Farm, Middle Point, Northern Territory, Australia were used to estimate crocodile breeding values (CBVs) for four breeding objectives: -reproductive output (Isberg et al., 2005a), -age at slaughter (Isberg et al., 2005b), -juvenile survival (Isberg et al., 2006a), and -number of scale rows (Isberg et al., 2006b). Whilst these breeding objectives allowed immediate implementation as a practical genetic selection tool with significant economic incentives for crocodile producers, further traits were of interest for potential inclusion. ...
... The simple method to count the number of scale rows (Isberg et al., 2006b) was used herein but a count was made on either side of the umbilical midline since Isberg et al. (2006b) only used the left side. The number of scale row splits is illustrated in Figure 2.3 and was a simple count of the number of scale rows that diverged. ...
... The simple method to count the number of scale rows (Isberg et al., 2006b) was used herein but a count was made on either side of the umbilical midline since Isberg et al. (2006b) only used the left side. The number of scale row splits is illustrated in Figure 2.3 and was a simple count of the number of scale rows that diverged. ...
The main objective of this project was to generate a large single nucleotide polymorphism (SNP) marker resource for later saturation of the genetic linkage map and fine mapping of quantitative trait loci (QTL). Another objective of this project was to learn more about basic crocodile biology, namely immune function and stress, and the underlying genetic function to evaluate their incorporation into CrocPLAN.
This report describes the development of new phenotypic trait panels for farmed saltwater crocodiles. Among these is the major crocodilian stress hormone, corticosterone (CORT), which should be useful for the development of animal welfare standards and the eventual selection of individuals in the future. Immune assays, some of which have never been previously used in crocodilians, were employed in this project to assess immune function. These immune assays, which are relatively easy to perform and cheap, could be employed in any farming setting to assess immune function in the future. Levels of estradiol (ESTR) and testosterone (TEST) are also detailed in this report, for the first time in the saltwater crocodile. At the same time as trying to expedite industry adoption of genetic improvement programs, it was necessary to expand on the current selection criteria available to gain a deeper insight into the breeding objectives already defined from RIRDC Project US-109A. The traits added were corticosterone (the main crocodilian stress hormone), two immune parameters, two sex hormones (testosterone and estradiol), two behaviour characters and four skin quality traits. Simultaneously, some of these traits could be used to gauge current industry practices which are set out in the “Code of Practice on the humane treatment of wild and farmed Australian crocodiles”. I am pleased to report that the lowest levels of corticosterone ever reported in saltwater crocodiles were found certifying the recommendations set out in the “code of practice”.
... As the international skin trade becomes more competitive, additional skin-quality traits, even those which do not currently receive a premium, may become more important when marketing crocodilian skins. Number of SR was previously identified among these prospective skin quality traits by Manolis et al. (2000), after which Isberg et al. (2004Isberg et al. ( , 2006b conducted quantitative analyses and recommended that number of SR be implemented as a breeding objective within the multi-trait genetic selection programme (Croc-PLAN). SR was reported to have a high heritability (h 2 0.37, SE: 0.03) as well as a high level of phenotypic variation, which could be exploited through a genetic improvement programme (Isberg et al. 2006b). ...
... Number of SR was previously identified among these prospective skin quality traits by Manolis et al. (2000), after which Isberg et al. (2004Isberg et al. ( , 2006b conducted quantitative analyses and recommended that number of SR be implemented as a breeding objective within the multi-trait genetic selection programme (Croc-PLAN). SR was reported to have a high heritability (h 2 0.37, SE: 0.03) as well as a high level of phenotypic variation, which could be exploited through a genetic improvement programme (Isberg et al. 2006b). Although increasing the number of SR in the belly skins of crocodiles does not currently receive an economic premium, it is a simple trait to measure and it is likely to be of economic value in the future. ...
... Family names and their respective sizes (in brackets) were as follows: 40A (52), 40B (74), 40F (38), 40H (42), 40J (89), 40K (71), 50A (54), 50K (13), 50M (33) and 50O (16). Families selected for inclusion in the Porosus Resource were identified based on the large variation in residuals for Inventory head length (InvHL) and SR after adjustment for fixed effects using the REML models described in Isberg et al. (2005bIsberg et al. ( , 2006b. ...
The recent generation of a genetic linkage map for the saltwater crocodile (Crocodylus porosus) has now made it possible to carry out the systematic searches necessary for the identification of quantitative trait loci (QTL) affecting traits of economic, as well as evolutionary, importance in crocodilians. In this study, we conducted genome-wide scans for two commercially important traits, inventory head length (which is highly correlated with growth rate) and number of scale rows (SR, a skin quality trait), for the existence of QTL in a commercial population of saltwater crocodiles at Darwin Crocodile Farm, Northern Territory, Australia. To account for the uncommonly large difference in sex-specific recombination rates apparent in the saltwater crocodile, a duel mapping strategy was employed. This strategy employed a sib-pair analysis to take advantage of our full-sib pedigree structure, together with a half-sib analysis to account for, and take advantage of, the large difference in sex-specific recombination frequencies. Using these approaches, two putative QTL regions were identified for SR on linkage group 1 (LG1) at 36 cM, and on LG12 at 0 cM. The QTL identified in this investigation represent the first for a crocodilian and indeed for any non-avian member of the Class Reptilia. Mapping of QTL is an important first step towards the identification of genes and causal mutations for commercially important traits and the development of selection tools for implementation in crocodile breeding programmes for the industry.
... Over 11 different species of crocodilians are farmed worldwide for their meat and skin products (1). Saltwater or estuarine crocodiles (Crocodylus porosus) are particularly prized for their superior skins, attributed to the absence of bony deposits (osteoderms) in their ventral scales, resulting in a higher number of small, evenly distributed scales (2)(3)(4). Key producers of C. porosus include Australia, Bangladesh, Indonesia, Malaysia, Papua New Guinea, the Philippines, and Thailand (1). In Australia, crocodile farming began in the 1970s, although a sustainable industry did not emerge until the 1980s (5,6). ...
Introduction
Understanding the impact of housing conditions on the stress responses in farmed saltwater crocodiles (Crocodylus porosus) is crucial for optimizing welfare and management practices.
Methods
This study employed a multi-omics methodology, combining targeted and untargeted LC–MS for metabolite, lipid, and hormone profiling with 16S rRNA gene sequencing for microbiome analysis, to compare stress responses and changes in fecal samples of crocodiles housed in single versus group pens. Metabolic responses to a startle test were evaluated through multivariate analysis, and changes post-stress were examined.
Results
A total of 564 metabolic features were identified. Of these, 15 metabolites were linked to the cortisol biosynthesis pathway. Metabolite origin analysis showed that 128 metabolites originated from the host, 151 from the microbiota, and 400 remained unmatched. No significant differences in fecal corticosterone levels were observed between single and group pens. However, metabolic profiling revealed distinct differences in stress responses: single pen crocodiles exhibited downregulation of certain compounds and upregulation of others, affecting pyrimidine and purine metabolism pathways when compared to grouped pen crocodiles, linked to altering energy associated induced stress. Additionally, fecal microbiome analysis indicated increased Firmicutes:Bacteroides (F:B) ratio in group-housed animals, suggesting greater stress.
Discussion
The study highlights that while traditional stress indicators like corticosterone levels may not differ significantly between housing conditions, metabolic and microbiome analyses provide deeper insights into stress responses. Single pens are associated with less metabolic disruption and potentially better health outcomes compared to group pens. These findings underscore the value of fecal microbiome and metabolomics in assessing animal welfare in farmed crocodiles.
... The cost of this production system is considerable, and includes additional general husbandry, maintenance of water quality and feeding. In a similar way to that used in the cattle industry, AI, in combination with frozen semen in the crocodile, has the potential to reduce the need for males on farm and dramatically reduce production costs, Moreover, crocodile AI would greatly facilitate the transfer and delivery of selected genetics for improvements in production traits (Isberg et al. 2003(Isberg et al. , 2005a(Isberg et al. , 2005b(Isberg et al. , 2006a(Isberg et al. , 2006b. Semen, rather than crocodiles, can be shipped from farm to farm at a reduced cost, and semen from wild animals could be used to improve genetic vigour without bringing males into captivity. ...
This review reports the current status of artificial breeding technology in the Crocodylia and the future requirements for the establishment of AI in the saltwater crocodile. Although there are challenges regarding safe restraint and immobilisation, semen collection of the saltwater crocodile by manual stimulation has proven effective in yielding sufficient volume and sperm concentrations for empirical and molecular analyses of sperm preservation and physiology. Nevertheless, there is still much to learn with respect to fundamental anatomy, physiology and behaviour in both sexes, but particularly in the female. Although lessons can be learned from successful AI in the alligator, the details of this research are not readily accessible. Future research needs to focus on the proximate factors of seasonality and the underlying control of the female’s annual reproductive cycle; this will require novel and innovative ways to collect blood samples without causing stress or injury, and ideally a dedicated crocodile research breeding colony. Because the saltwater crocodile is a farmed species, there is likely to be sufficient impetus for the application of assisted breeding technology to drive future productivity in the industry. These developments will also have benefits for the genetic and reproductive management of endangered captive populations.
... The upper surface of the top jaw becomes more shrunken in large adult males. Juveniles C. porosus have more oval scales than other crocodile species, although belly scales are rectangular, even and relatively small (Isberg et al., 2006). C. porosus are normally green or pale tan in colour with black stripes and spots on the body and tail but they became paler and less colourful after reaching adult stage. ...
This study is designed to gather information on historical exploitation and ongoing HCC; recent distribution and ecology of crocodile and genetic relationship of crocodile population in Sarawak, to aid sustainable crocodile management and finding solutions for mitigating the HCC. Historical data saw a connection between the exploitation of crocodile with decreasing trend of HCC in Sarawak from the Rajah Brooke era (1900 – 1941) until the post-war period (1946 – 1979), and an increasing trend of HCC from 1980 until 2017 in response to the recovery of the animal populations. Since 1900, crocodile attacks had been occurred in 22 major river basins (RB) in Sarawak, suggesting that the reptile has been widely dispersed throughout all major river basins in the state. For 118 years (1900 – 2017), the highest number of crocodile attacks were recorded in Lupar RB (22.2%) and the attacks had happened up to the inland areas of Belaga and Pelagus in Rajang RB. Further analysis of incidents show crocodile attacks were associated with the human activities pattern, where more attacks involved male victims (84.4%) and adults from age 31 to 40 years old (19.3%). The data also revealed that crocodile attacks in Sarawak could happen anytime regardless of the time, month, season, lunar cycle or tidal. However, more attacks were recorded during the daylight, in the months of March and April, during the Northeast monsoon, at the nights of the first quarter of the lunar cycle and at the time of high tide. Furthermore, fishing (25.2%) and bathing (24.4%) possess the highest risk of crocodile attack in Sarawak, clearly showed that crocodiles are more likely to attack when the victim is in water. Crocodile survey in selected tributaries in Rajang RB showed the distribution of the reptiles throughout the river basin with higher crocodile density at the lower region, the highest density was in Igan River (1.37 individuals/km); while in the middle and upper regions had recorded relatively low density with the lowest density recorded was in Katibas River (0.06 individuals/km) and no crocodile was spotted in Kanowit River. Four out of eight surveyed rivers in Rajang RB recorded increase in the density of crocodile compare to previous survey suggesting that the crocodile population in the river basin is experiencing recovery. The presence of crocodile in different regions (lower, middle and upper) of Rajang RB indicated that C. porosus in Sarawak live in wide range of habitats; from large salt water river system and small tidal tributaries (near to estuary) in lower region into hypo-saline or fresh water non-tidal tributaries in the middle and upper regions. Variation in term of density and distribution of crocodile between the different regions are mainly influenced by the saline characteristic of the river, habitats and the abundance of food sources for crocodile. Based on the analysis of DNA microsatellite sequence data, distinctive subpopulations of C. porosus according to geographical area (river basin) could be observed. High gene flow (Nm) among the crocodile subpopulations suggests frequent movements of the reptile happen across the river basins throughout Sarawak. In general, populations of C. porosus in Sarawak are experiencing expansion as supported by the mismatch distribution and evolutionary neutrality test data, suggesting that populations of crocodile in Sarawak are panmictic population. The findings of the present study imply that increasing of crocodile attacks is associated with the recovery and increased distribution of the reptile in Sarawak, thus crocodile management should emphasis on mitigating HCC and simultaneously continue the efforts for conservation of crocodile and its habitat.
Keywords: Crocodylus porosus, human-crocodile conflict, recovery, expansion.
... Unblemished crocodile skin was defined as having no grossly visible abrasions or defects with normal, intact keratin overlaying the scale ( Figure 2A). To reduce any variation that may be present in different belly skin regions (Grice and Segre 2011), all blemish-free crocodile skins swabs were standardised around the 15 th scale row down from the collar adjacent to the midline (Isberg et al. 2006). If both adjacent midline scales on the 15 th row were blemished, then either the 14 th or 16 th row was used. ...
... Unblemished crocodile skin was defined as having no grossly visible abrasions or defects with normal, intact keratin overlaying the scale ( Figure 2A). To reduce any variation that may be present in different belly skin regions (Grice and Segre 2011), all blemish-free crocodile skins swabs were standardised around the 15 th scale row down from the collar adjacent to the midline (Isberg et al. 2006). If both adjacent midline scales on the 15 th row were blemished, then either the 14 th or 16 th row was used. ...
Background
The global crocodilian skin market is currently in oversupply. As a result, the tanneries can now be very selective about the quality of skins they purchase. The challenge to producers is to meet these quality standards. A part of this challenge is to understand the risk of pathogens to crocodile skin quality.
Aims/objectives
Collectively, the aims of this project were to understand crocodile skin microflora and to better understand the threats to skin quality.
Methods used
To characterise skin microflora, 16SrRNA tag sequencing was used to compare wild and captive skins, whilst the identification of blemish causation was achieved using specific genetic sequences to screen for particular organisms. A survey of crocodile skins allowed the infection dynamics of poxvirus to be understood.
Results/key findings
Dermatophilus sp infection is not isolated to focal lesions as first thought. Dermatophilus sp. is also implicated, at high reads, in linear lesions. It continues to be problematic in focal lesions but can be more subtle than when first described as “brown spot”. Dermatophilus sp can be easily confused with early active poxvirus lesions. Wild saltwater crocodile have a substantially lower presence of Dermatophilus sp. suggesting that intensification has allowed it to develop an ecological niche in farm production settings.
While Dermatophilus sp. and poxvirus were identified from skin lesions with high prevalence, the Crocodyline herpesvirus and the Kunjin strain of West Nile virus were also identified. The prevalence of poxvirus is particularly high in grower pens but the infection dynamics on the two farms studied are contrary to each other. On one farm, poxvirus prevalence decreases as the animals approach finishing size and therefore has relatively little impact on production time. However, on the other farm, the number of lesions, particularly early stage lesions, increases and delays harvest times thus increasing production costs.
Implications and Recommendations
Developing quantitative genetic methods to detect these pathogens and assess different hygiene regimes is essential. This will allow producers to quantitatively assess the efficacy of their current regimes and make appropriate decisions. Reducing the impact of these pathogens will be crucial to delivering the skin quality demanded.
... While harvesting eggs (and adults for breeding) from the wild has been an effective conservation strategy, it means that no selection for performance ability under intensive production systems can be undertaken. The opportunity is to exploit the genetic variation and Isberg et al. (2004;2005a;2005b;2006a;2006b) assessed the potential of implementing genetic improvement noting that there were substantial economic benefits to be gained. For example, survival heritability estimates for crocodiles are much higher (animal model = 0.28 -0.60) than those reported for many other production species (Isberg et al. 2009). ...
In the last five decades, the Australian saltwater crocodile population has recovered from near extinction back to pre-hunting levels because of a highly successful conservation strategy. Farming has been crucial in the recovery by providing economic-incentives to landowners to conserve the species and its habitat. However, farming a species that has evolved little since the dinosaurs has unique challenges compared to traditional livestock species. The lack of selection and domestication (wild harvested eggs) equates to large phenotypic variation and, given the industry's infancy, has relied on developing husbandry approaches that balance the physiological needs of crocodiles and production outputs. This approach appears to have worked to satisfy the welfare needs of the crocodiles as well although improvements are continually being sought. Novel equipment and handling techniques have been developed to ensure safe working environments for staff whilst not compromising animal welfare. The primary product is the skin, which is also unique as skins/hides are normally a by-product of traditional farming operations. This brings more idiosyncratic challenges as buyers demand blemish-free skins that will produce flawless high-end fashion products. Overall, in a short period of time, the Australian crocodile industry has emerged as an economically-viable, sustainable conservation-based industry but still has many challenges ahead as we continue to learn about the husbandry and welfare requirements of these dinosaurian descendants.
... Table 1 shows crocodilian species of economic importance. Of these, C. porosus skins are generally held to be superior due to the lack of bony deposits (osteoderms) in the ventral belly scales as well as the high number and general regularity of the scale rows (Thorbjarnarson, 1999;Isberg et al., 2006). This review will initially provide a brief overview of the histological structure of crocodilian belly skin noting the relevance of various skin components to leather production. ...
... To achieve this objective, crocodile farming must remain economically viable. As such, previous studies have been conducted to understand the significant biotic and abiotic factors affecting various production traits including age at harvest (Isberg et al., 2005), juvenile survival (Isberg et al., 2006a) and number of scale rows (Isberg et al., 2006b;Miles et al., 2010). However, many of the factors that could underlie these production traits remain unknown. ...
... Saltwater crocodile (Crocodylus porosus) farming is a rapidly evolving agricultural practice and in order to keep up with the industry expansion their will need to be corresponding improvements in productivity and efficiency. Although much of the crocodile production in Australia currently relies on the wild harvesting of eggs, future genetic improvement of desirable phenotypes (Isberg et al., 2003(Isberg et al., , 2005a(Isberg et al., , 2005b(Isberg et al., , 2006a(Isberg et al., , 2006b and the ultimate environmental sustainability of industry are likely to be best managed through "on farm" captive breeding and egg production; it is within this context, that we propose the development of technology leading towards the establishment of artificial insemination in the crocodile. Althouse (2007) has defined artificial insemination as the process of mechanically and unnaturally depositing semen into the female reproductive tract with the goal of achieving conception, highlighting the drivers that lead to the implementation of this practice in a range of animal industries. ...
... Quality specifications of raw crocodile skins imposed by skin buyers have become increasingly important over recent years as the worlds' production of crocodilian skins increases. Although saltwater crocodile (Crocodylus porosus) belly skin remains in high demand due to its desirable traits of evenly distributed small scales, the definition of a "blemish-free" skin (Isberg et al. 2004) is becoming increasingly rigorous. However, publications detailing the pathological and epidemiological aspects of pre-harvest crocodilian skin blemishes are scarce. ...
Minimising stress in farmed crocodiles is not only important for improving animal welfare, but may also improve skin blemish healing and infection resistance, which influence the quality of the final skin product. Forty near-harvest size saltwater crocodiles (1.6-1.8 m TL) from two Australian farms were sampled to evaluate the effect of different pen types (communal pens n=20; individual pens n=20) on stress as indicated by plasma corticosterone. Blood samples were taken within three minutes of immobilisation and analysed using a commercial enzyme immunoassay kit. There was no relationship with animal size (P=0.16), between farms (P=0.86), pen types (P=0.69), communal pens between farms (P=0.28) or individual pens between farms (P=0.24). Based on corticosterone levels, it appears that individual pens do not cause significantly more stress on harvest-size animals than communal pens. Individual pens meet their design specifications by achieving comparable healing rates of belly skin blemishes as communal pens without compromising animal welfare and minimising the possibility of new blemishes.
... Although still an emerging livestock industry, the Australian crocodile industry, following the lead of other livestock industries, has recently developed a comprehensive genetic improvement program[22]. Research efforts have thus far focused on genetic and phenotypic parameter estimation for selection objectives and selection criteria required for multitrait index selection[22][23][24][25][26]. However, this type of animal selection occurs with little or no knowledge of what is occurring at the DNA level. ...
Genome elucidation is now in high gear for many organisms, and whilst genetic maps have been developed for a broad array of species, surprisingly, no such maps exist for a crocodilian, or indeed any other non-avian member of the Class Reptilia. Genetic linkage maps are essential tools for the mapping and dissection of complex quantitative trait loci (QTL), and in order to permit systematic genome scans for the identification of genes affecting economically important traits in farmed crocodilians, a comprehensive genetic linage map will be necessary.
A first-generation genetic linkage map for the saltwater crocodile (Crocodylus porosus) was constructed using 203 microsatellite markers amplified across a two-generation pedigree comprising ten full-sib families from a commercial population at Darwin Crocodile Farm, Northern Territory, Australia. Linkage analyses identified fourteen linkage groups comprising a total of 180 loci, with 23 loci remaining unlinked. Markers were ordered within linkage groups employing a heuristic approach using CRIMAP v3.0 software. The estimated female and male recombination map lengths were 1824.1 and 319.0 centimorgans (cM) respectively, revealing an uncommonly large disparity in recombination map lengths between sexes (ratio of 5.7:1).
We have generated the first genetic linkage map for a crocodilian, or indeed any other non-avian reptile. The uncommonly large disparity in recombination map lengths confirms previous preliminary evidence of major differences in sex-specific recombination rates in a species that exhibits temperature-dependent sex determination (TSD). However, at this point the reason for this disparity in saltwater crocodiles remains unclear.This map will be a valuable resource for crocodilian researchers, facilitating the systematic genome scans necessary for identifying genes affecting complex traits of economic importance in the crocodile industry. In addition, since many of the markers placed on this genetic map have been evaluated in up to 18 other extant species of crocodilian, this map will be of intrinsic value to comparative mapping efforts aimed at understanding genome content and organization among crocodilians, as well as the molecular evolution of reptilian and other amniote genomes. As researchers continue to work towards elucidation of the crocodilian genome, this first generation map lays the groundwork for more detailed mapping investigations, as well as providing a valuable scaffold for future genome sequence assembly.
This report summarises efforts to construct the first genetic linkage map for the saltwater crocodile (Crocodylus porosus), and subsequent investigation into the presence and positioning of quantitative trait loci (QTL) for economically important traits in farmed saltwater crocodiles. Linkage and QTL mapping exercises will contribute significantly to elucidation and characterisation of the crocodile genome, and represent an important first step towards the development of genetic improvement tools for implementation in industry breeding programs. One of the major objectives of this research was to generate the requisite genomic resources to carry out genetic mapping studies in saltwater crocodiles. As such, herein we describe the development of a microsatellite marker resource, a DNA resource, a first generation genetic linkage map, a refined karyotype for C.porosus, and a proof of principle QTL study identifying the first QTL for crocodilian, or indeed any other non-avian reptile.
Semen collected from 10 saltwater crocodiles (Crocodylus porosus) was used to investigate sperm in vitro manipulation and preservation. Preliminary studies revealed that phosphate buffered saline (PBS) without Ca2 +, Mg2 + and egg yolk (EY) was a suitable extender for studies of sperm physiology. Spermatozoa diluted in PBS showed no change in survival [% motility (M), rate of sperm movement (R) and % plasma membrane integrity (PI)] when diluted over a range of 1:1 to 1:16. Except for a small decline in PI, there was no change in sperm survival when semen diluted without EY was cooled rapidly to and rewarmed from 0 °C. The addition of EY (0, 5, 10 and 20% v/v) had no beneficial effect on sperm survival when incubated in PBS for 1 h at 30 °C or after 24 h storage at 4 °C. Whilst crocodile spermatozoa exposed to a range of anisotonic media and then returned to solutions of 390 mosM kg− 1 retained their M from 220 to 390 mosM kg− 1, PI remained high in hypotonic media (25–280 mosM kg −1); spermatozoa showed an increase (P < 0.05) in the incidence of flagellar coiling (FC) with increasing hypotonic conditions. The adverse effect of anisotonic conditions on sperm M and FC recovered somewhat when sperm were returned to the 390 mosM kg −1 media, but not to pre-treatment levels. Exposure of crocodile spermatozoa to respective concentrations of 0.68 M, 1.35 M and 2.7 M glycerol, dimethylsulphoxide (DMSO), and dimethylacetamide (DMA) after 2 h storage at 4 °C (equilibration) resulted in a reduction in M, but no change in PI. Sperm cryopreserved in the same cryoprotectant media within 0.25 mL straws at − 6 °C/min in a programmable freezer and thawed at 37 °C for 1 min showed a major decline (P < 0.05) of M but there was moderate protection of PI (DMA 2.7 M — 17.7 ± 4.4; DMSO 2.7 M — 22.7 ± 1.4 and glycerol 2.7 M — 25.7 ± 6.4). Sperm thawed and immediately washed to remove the cryoprotectant showed an improvement (P < 0.05) in PI but not M. Future studies of crocodile sperm preservation should explore the apparent disjunction between low levels of M and the high tolerance of the plasma membrane to anisotonic conditions and cryoprotectant toxicity.
The first evidence of genetic linkage and sex-specific recombination in the order Crocodylia is reported. This study was conducted using a resource pedigree of saltwater crocodiles consisting of 16 known-breeding pairs (32 adults) and 101 juveniles. A total of 21 microsatellite loci were available for analysis. Ten of the 21 loci showed linkage with 4 linkage groups: 3 pairwise (Cj131/Cj127, CUD68/Cj101, and Cj107/Cp10) and 1 four-locus (Cj122, CUD78, Cj16, and Cj104) being found. Linkage analysis on the 21 loci revealed evidence of sex-specific differences in recombination rates. All 5 nonzero interlocus intervals were longer in females than in males, with the 4-loci linkage group 3-fold longer in females than in males (41.63 cM and 14.1 cM, respectively). This is the first report of sex-specific recombination rates in a species that exhibits temperature-dependent sex determination.
Half of the 22 extant crocodilians show evidence of temperature-dependent sex determination (TSD). We examine evidence for TSD in 11 species by reviewing reports on five and presenting new data for six. The female-male pattern (FM; females at low temperature, males at high temperature) attributed to Alligator mississippiensis and Caiman crocodilus are here revised to be female-male-female (FMF; males at intermediate temperature, females at low and high temperatures). A similar pattern characterizes Crocodylus palustris, C. moreletii, C. siamensis, and Gavialis gangeticus based on new data; published accounts establish a FMF pattern in Crocodylus porosus, C. johnstoni, and C. niloticus. TSD apparently occurs in Paleosuchus trigonatus and Alligator sinensis, but patterns are not yet documented. In the well-studied species, the incubation temperatures for FM transitions are congruent, but MF transition temperatures differ among species. In A. mississippiensis, 100% males are produced over a range of constant incubation temperatures, whereas in C. johnstoni, only low proportions of males are produced at any constant temperature.
Most traits and disorders have a multifactorial background indicating that they are controlled by environmental factors as well as an unknown number of quantitative trait loci (QTLs). The identification of mutations underlying QTLs is a challenge because each locus explains only a fraction of the phenotypic variation. A paternally expressed QTL affecting muscle growth, fat deposition and size of the heart in pigs maps to the IGF2 (insulin-like growth factor 2) region. Here we show that this QTL is caused by a nucleotide substitution in intron 3 of IGF2. The mutation occurs in an evolutionarily conserved CpG island that is hypomethylated in skeletal muscle. The mutation abrogates in vitro interaction with a nuclear factor, probably a repressor, and pigs inheriting the mutation from their sire have a threefold increase in IGF2 messenger RNA expression in postnatal muscle. Our study establishes a causal relationship between a single-base-pair substitution in a non-coding region and a QTL effect. The result supports the long-held view that regulatory mutations are important for controlling phenotypic variation.
and in many instances the estimate of a phenotypic correlation is reported smaller in magnitude than that of the corresponding genetic correlation, e.g. with certain poultry records, in Lerner & Cruden [1948], sheep records in Morley [1951] and with certain dairy records in VanVleck [1960] and Searle [1961]. Such results may seem a little unexpected at first sight since phenotype includes genotype and one might anticipate the correlation between phenotypes to be larger than that between genotypes. When estimates have not followed this pattern the explanation is sometimes given that a phenotypic correlation less than a genetic correlation is the result of a negative environmental correlation in the records of the two traits. This paper investigates the relationship between these three correlations on the basis of a linear model, and demonstrates the situations in which this explanation is correct. Other comparisons are also made.
Best Linear Unbiased Prediction (BLUP) has become the most widely accepted method for genetic evaluation of domestic livestock. Since its introduction, the method has evolved and despite this there is no simple text on the application of linear models to the prediction of breeding values. This book has been written with a good balance of theory and application to fill this gap. Equations for partitioning breeding values into contributions from various sources of information are derived under the various models. Recent developments in the analysis of longitudinal data with random regression models and the inclusion of genetic marker information in the evaluation of animals have been incorporated. Overall the book has been thoroughly updated since the first edition was published in 1996.
Crocodile morphometric (head, snout-vent and total length) measurements were recorded at three stages during the production chain: hatching, inventory [average age (+/-SE) is 265.1 +/- 0.4 days] and slaughter (average age is 1037.8 +/- 0.4 days). Crocodile skins are used for the manufacture of exclusive leather products, with the most common-sized skin sold having 35-45 cm in belly width. One of the breeding objectives for inclusion into a multitrait genetic improvement programme for saltwater crocodiles is the time taken for a juvenile to reach this size or age at slaughter. A multivariate restricted maximum likelihood analysis provided (co)variance components for estimating the first published genetic parameter estimates for these traits. Heritability (+/-SE) estimates for the traits hatchling snout-vent length, inventory head length and age at slaughter were 0.60 (0.15), 0.59 (0.12) and 0.40 (0.10) respectively. There were strong negative genetic (-0.81 +/- 0.08) and phenotypic (-0.82 +/- 0.02) correlations between age at slaughter and inventory head length.
Repeatability and phenotypic correlations were estimated for saltwater crocodile reproductive traits. No pedigree information was available to estimate heritability or genetic correlations, because the majority of breeder animals on farms were wild-caught. Moreover, as the age of the female breeders could not be accounted for, egg-size measurements were used as proxies. The reproductive traits investigated were clutch size (total number of eggs laid), number of viable eggs, number of eggs that produced a live, healthy hatchling, hatchability, average snout-vent length of the hatchlings and time of nesting. A second data set was also created comprising binary data of whether or not the female nested. Repeatability estimates ranged from 0.24 to 0.68 for the measurable traits, with phenotypic correlations ranging from -0.15 to 0.86. Repeatability for whether a female nested or not was 0.58 on the underlying scale. Correlations could not be estimated between the measurement and binary traits because of confounding. These estimates are the first published for crocodilian reproduction traits.
Markets for Skins and Leather from the Goat
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Crocodiles: Inside Out Phenotypic, genetic and environmen-tal correlations
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The effects of incubation temperature on sex determination and embryonic development rate in Crocodylus johnstoni and C. porosus Wildlife Manage-ment: Crocodiles and Alligators
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Webb G.J.W., Beal A.M., Manolis S.C., Dempsey K.E. (1987) The effects of incubation temperature on sex determination and embryonic development rate in Crocodylus johnstoni and C. porosus. In: G.J.W. Webb, P.J. Whitehead, S.C. Manolis (eds), Wildlife Manage-ment: Crocodiles and Alligators. Surrey Beatty and Sons, Chipping Norton, Australia, pp. 507–531.
Production traits in C
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Information Systems for New Animal Industries Rural Industries Research and Development Corporation, Canberra, Australia. Publ. No. 98/139 Available at: http://www.rirdc.gov
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Improving the Quality of Australian Crocodile Skins. Rural Industries Research and Development Corporation
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The effects of incubation temperature on sex determination and embryonic development rate in Crocodylus johnstoni and C. porosus
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Webb G.J.W., Beal A.M., Manolis S.C., Dempsey K.E.
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Markets for Skins and Leather from the Goat, Emu, Ostrich, Crocodile and Camel Industries. Rural Industries Research and Development Corporation
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MacNamara K., Nicholas P., Murphy D., Riedel E., Goulding B., Horsburgh C., Whiting T., Warfield B. (2003)
Markets for Skins and Leather from the Goat, Emu,
Ostrich, Crocodile and Camel Industries. Rural Industries Research and Development Corporation, Canberra,
Australia. Publ. No. 02/142. Available at: http://www.
rirdc.gov.au/reports/NAP/02-142.pdf. Accessed 21
November, 2005.
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