Article

The parasite community of the sharks Galeus melastomus , Etmopterus spinax and Centroscymnus coelolepis from the NW Mediterranean deep-sea in relation to feeding ecology and health condition of the host and environmental gradients and variables

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Abstract

The parasite communities of sharks have been largely neglected despite the ecological importance and vulnerability of this group of fishes. The main goal of the present study is to describe the parasite communities of three deep-dwelling shark species in the NW Mediterranean. A total of 120 specimens of Galeus melastomus, 11 Etmopterus spinax and 10 Centroscymnus coelolepis were captured at 400-2200m depth at two seasons and three localities off the mainland and insular slopes of the Balearic Sea. Environmental and fish biological, parasitological, dietary, enzymatic and histological data were obtained for each specimen, and the relationships among them tested. For G. melastomus, E. spinax and C. coelolepis a total of 15, two and eight parasite species were respectively recovered. The parasite community of G. melastomus is characterized by high abundance, richness and diversity, and the cestodes Ditrachybothridium macrocephalum and Grillotia adenoplusia dominate the infracommunities of juvenile and adult specimens, respectively. A differentiation of parasite communities, linked to a diet shift, has been observed between ontogenic stages of this species. E. spinax displays a depauperate parasite community, and that of C. coelolepis, described for the first time, shows moderate richness and diversity. Detailed parasite-prey relationships have been discussed and possible transmission pathways suggested for the three hosts. Parasites were mostly related to high water turbidity and O2 levels, which enhance zooplankton proliferation and could thus enhance parasite transmission. The nematodes Hysterothylacium aduncum and Proleptus obtusus were linked to high salinity levels, as already reported by previous studies, which are associated to high biomass and diversity of benthic and benthopelagic crustaceans. A decrease of acetylcholinesterase activity and lower hepatosomatic index, possibly linked to infection-related stress, have been observed. Lesions associated to encapsulated larvae of G. adenoplusia have been observed in the muscle of G. melastomus, especially in the tail region, which can be indicative of the hunting strategy of its final host and may compromise the escape response of G. melatomus thus facilitating parasite transmission.

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... As such, parasite communities of sharks could be used as useful indicators of biodiversity, food web structure, and environmental stress 2,5,13,17 . Among sharks living in the north-eastern Atlantic and Mediterranean Sea, Scyliorhinus canicula (Linnaeus, 1758), Galeus melastomus Rafinesque 1810, and Etmopterus spinax (Linnaeus, 1758) are carnivorous generalist occupying the mid-high marine trophic levels, thus playing not only an important OPEN role as predators, but also serving as prey for largest taxa [18][19][20][21][22] . Given the key position in trophic food webs, they also host a wide variety of heteroxenous parasites; despite of that, comparative analyses of their parasites communities only exist from the Balearic Sea (north-western Mediterranean Sea) [18][19][20] . ...
... Among sharks living in the north-eastern Atlantic and Mediterranean Sea, Scyliorhinus canicula (Linnaeus, 1758), Galeus melastomus Rafinesque 1810, and Etmopterus spinax (Linnaeus, 1758) are carnivorous generalist occupying the mid-high marine trophic levels, thus playing not only an important OPEN role as predators, but also serving as prey for largest taxa [18][19][20][21][22] . Given the key position in trophic food webs, they also host a wide variety of heteroxenous parasites; despite of that, comparative analyses of their parasites communities only exist from the Balearic Sea (north-western Mediterranean Sea) [18][19][20] . ...
... The total mean abundance, species richness, Berger-Parker dominance index, and the Brillouin index of diversity were used as overall descriptors of infracommunities for each host species examined [18][19][20]42 . Total mean abundance was measured as the mean number of individuals of all parasite species, while species richness as the number of parasite species harboured by each shark specimen 42 . ...
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Article
Sharks play a key role in the functioning of marine ecosystems and maintenance of trophic web balance, including life cycles of parasites co-occurring in their habitats. We investigated the structure of parasite communities of three sympatric shark species (Etmopterus spinax, Galeus melastomus, and Scyliorhinus canicula) and explored both the influence of host features in shaping the communities and their role as biological indicators of environment stability in the Gulf of Naples (central Mediterranean Sea), a geographical area characterized by strong anthropic pressure. Parasites found were all trophic transmitted helminths with a complex life cycle, except Lernaeopoda galei, that is a ecto-parasite copepod. Communities were all similarly impoverished with 4–5 component species and low values of species richness and diversity. Higher abundance of cestode larvae of the genus Grillotia was found in G. melastomus, although their dominance in all host species suggests that the three sharks have a similar role as intermediate/paratenic hosts in local food webs. Similarly, high abundance of Grillotia larvae could also suggest the occurrence of high abundance of largest top predators in the area. Host morphological (fork length in S. canicula and G. melastomus and body condition index in G. melastomus) and physiological (sex and gonadosomatic and hepatosomatic indices in S. canicula) variables were differently correlated to parasite community structures depending by host species. Potential reasons for the present impoverished parasite communities are discussed.
... For parasites with a life cycle embedded within the marine food webs, biotic factors are also important to evaluate the physiological condition of the fish and the way the fish get resources from the environment, and also the probability for a host to acquire parasites. Therefore, the study of relationships between biotic factors and number of parasites within a host might also provide information about the biology and ecology of both hosts and parasites (Dallares, 2016;Dallares et al., 2016Dallares et al., , 2017Dallares, Padros et al., 2017;Palm, 2004;Santoro, Iaccarino et al., 2020;Timi & Poulin, 2020). ...
... For parasites with a life cycle embedded within the marine food webs, biotic factors are also important to evaluate the physiological condition of the fish and the way the fish get resources from the environment, and also the probability for a host to acquire parasites. Therefore, the study of relationships between biotic factors and number of parasites within a host might also provide information about the biology and ecology of both hosts and parasites (Dallares, 2016;Dallares et al., 2016Dallares et al., , 2017Dallares, Padros et al., 2017;Palm, 2004;Santoro, Iaccarino et al., 2020;Timi & Poulin, 2020). ...
... In Mediterranean Sea, recent records of larval forms of Grillotia infecting sharks include two reports in G. melastomus, in which the larvae were originally reported as Grillotia sp. (Dallares, Padros et al., 2017) and then as G. adenoplusia (Dallares et al., 2017), with a prevalence of infection ranging from 7.6% to 28.6% and a maximum mean abundance of 0.48 depending from the sampling localities, whereas no Grillotia specimens were detected in 41 individuals of S. canicula from the same locality (Dallares, Padros et al., 2017;Dallares et al., 2017). The difference in infection values between the North-Western Mediterranean studies (Dallares, Padros et al., 2017;Dallares et al., 2017) and the present one might be related to the different geographical features and high productivity in terms of food webs at the time of the sampling, two variables that may affect the number of intermediate and definitive hosts present in the area (Collins et al., 1984;Dallares, Padros et al., 2017;Hassan et al., 2002;Palm & Overstreet, 2000;Santoro et al., 2019;Santoro, Iaccarino et al., 2020). ...
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Article
Aim Trypanorhyncha cestodes comprise a wide range of heteroxenous parasites infecting elasmobranchs as definitive hosts. Limited data exist on the larval infection of these cestodes and the role of intermediate and paratenic hosts in the life cycle of these parasites. We investigated the factors that determine the occurrence and the level of infection of Grillotia plerocerci in the skeletal muscles of various benthonic sharks and analyzed the parasites through an integrative taxonomic approach. Location Mediterranean Sea. Methods Sharks obtained as bycatch of commercial trawling activities (i.e., Etmopterus spinax, Galeus melastomus, and Scyliorhinus canicula) were used in this study. Data from a limited number of Dalatias licha and Scyliorhinus stellaris were also included. Grillotia plerocerci were molecularly characterized using the partial 28S large subunit rDNA. Boosted regression trees were used to model the relationship between the abundance of infection with both morphological and physiological predictors in each host. Results Plerocerci of Grillotia were detected in all shark species except S. stellaris. Host species significantly differed in terms of parasite abundance, with the highest and lowest prevalence and abundance of infection detected in G. melastomus and E. spinax, respectively. The relative influence of the traits involved in explaining the parasite abundance was related to the host size in G. melastomus, while both morphology- and physiology-related traits explained the patterns observed in E. spinax and S. canicula. The 28S rDNA sequences shared an identity of ∼99.40% with a Grillotia species previously found in the Mediterranean Sea. At intraspecific level, two different genotypes were found. A first type was retrieved only from D. licha, whereas a second type was found in G. melastomus, E. spinax, and S. canicula. Main conclusions Present results suggest that the two genotypes could be involved in different consumer-resource systems and confirm most of the examined shark species as transport hosts of Grillotia species for unknown larger top predators.
... Because many trophically-transmitted parasites have complex life-cycles involving more than one host, a given parasite community is largely shaped by the structure of the local food web and can provide valuable information on the position that the host occupied within it at a certain time (Marcogliese, 2002;Valtonen et al., 2010;Culurgioni et al., 2015). Host diet shifts, for example, which involve the consumption of different intermediate hosts, are rapidly reflected in changes in parasite community composition and structure (Münster et al., 2015;Dallarés et al., 2017a). ...
... Recently, considerable efforts have been devoted to the characterization of parasite communities in fish species of the continental shelf and slope of the continental coast of the Western Mediterranean off Spain (e.g. Pérez-del-Olmo et al., 2008Grau et al., 1999;Carreras-Aubets et al., 2011, 2012Mateu et al., 2014;Dallarés et al., 2014Dallarés et al., , 2016Dallarés et al., , 2017aDallarés et al., , 2017bConstenla et al., 2015;Pérez-i-García et al., 2015. Most of these studies have addressed in detail the influence of host biology and ecology, and of environmental variables, on the composition and structure of parasite communities in a range of fish species. ...
... The two species differed with respect to fish density (distinctly greater in P. acarne), vagility (much lower in P. acarne) and prey composition (Fig. 2). The suprabenthos-feeder Pagellus acarne was found to feed predominantly on teleosts, whose consumption has been associated with more diverse and abundant parasite faunas (Marcogliese, 2002;Dallarés et al., 2017a) whereas the epibenthos feeder P. erythrinus mainly preyed on infaunal invertebrates and decapods. ...
Article
We explored the relationships between features of host species and their environment, and the diversity, composition and structure of parasite faunas and communities using a large taxonomically consistent dataset of host-parasite associations and host-prey associations, and original environmental and host trait data (diet, trophic level, population density and habitat depth vagility) for the most abundant demersal fish species off the Catalonian coast of the Western Mediterranean. Altogether 98 species/taxa belonging to seven major parasite groups were recovered in 683 fish belonging to 10 species from seven families and four orders. Our analyses revealed that (i) the parasite fauna of the region is rich and dominated by digeneans; (ii) the host parasite faunas and communities exhibited wide variations in richness, abundance and similarity due to a strong phylogenetic component; (iii) the levels of host sharing were low and involved host generalists and larval parasites; (iv) the multivariate similarity pattern of prey samples showed significant associations with hosts and host trophic guilds; (v) prey compositional similarity was not associated with the similarity of trophically transmitted parasite assemblages; and (vi) phylogeny and fish autecological traits were the best predictors of parasite community metrics in the host-parasite system studied.
... Of the 509 species of sharks known to date, no fewer than 250 are considered deep-sea species [58]. Parasitological studies of species that inhabit these ecosystems focus on the taxonomic description of some species or new host records, but few include the analysis of the parasite community [14,15,25,28]. For the Southeastern Pacific Ocean (SEPO herein and after), the same scenario is evident. ...
... For the infracommunity level, we calculated the richness (number of parasite species per examined host), abundance (number of parasite individuals per examined host) and diversity (Brillouin index) using PRIMER v6, parasite species accumulation curves were constructed using the ''vegan'' package in R freeware [44]. The Berger-Parker dominance index was calculated as the number of individuals of the most abundant parasite species divided by the total number of parasites in a given fish host as indicated by Dallarés et al. [14]. The descriptors Shannon, Simpson and Inverse Simpson diversity index were calculated at the community component level using the ''vegan'' package in R freeware. ...
... Our data align well with this pattern for both host species analysed. These authors also suggest that [14,25,28]. Our data suggest that E. granulosus shows the highest richness among members of this genus (14 taxa) based on the published quantitative data (Supplementary material), but the integration of published taxonomic information (14 articles from seven localities) indicates the presence of 23 species, with Cestoda being the best represented group (14 taxa) (Supplementary material). ...
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Article
Two deep-sea shark species were obtained as by-catch of the local fishery of the Patagonian toothfish, Dissostichus eleginoides, at depths ranging from 1000 to 2200 m off central and northern Chile. A total of 19 parasite taxa were found in 133 specimens of the southern lanternshark, Etmopterus granulosus, (n = 120) and largenose catshark, Apristurus nasutus, (n = 13). Fourteen taxa (four Monogenea, one Digenea, four Cestoda, one Nematoda, two Copepoda, one Annelida and one Thecostraca) were found in E. granulosus, whereas five taxa (one Monogenea, two Cestoda and two Nematoda) were found in A. nasutus. Representatives of Cestoda showed higher values of prevalence and a greater intensity of infection; this pattern is consistent with reports for elasmobranchs, but the monogenean richness was higher than that previously reported for related deep-sea sharks. Regarding E. granulosus, a positive and significant correlation between host length and abundance was found for six (four ectoparasites, one mesoparasite, and one endoparasite) of the 14 taxa recorded, but prevalence was significantly correlated with host length only for the monogenean Asthenocotyle sp. Although the sample size for A. nasutus was limited, we compared richness, abundance, diversity and evenness at the infracommunity and component community levels. All of these variables were higher for E. granulosus, but at the infracommunity level, abundance was higher for A. nasutus. All the parasite taxa (except two) represent new host and geographical records.
... In general, benthopelagic species such as C. alleni and C. laticeps are known to be infected by more parasites than those with pelagic habits, which is indicative of exposure to a broader spectrum of parasites through consumption of a variety of prey that can act as potential transmitters (Campbell et al., 1980;Marcogliese, 2002). However, richness, diversity and abundance of parasite assemblages of Cataetyx spp., and mostly for C. alleni, were low compared to other deep-sea fish of the same waters (Constenla et al., 2015;Dallarés et al., 2014Dallarés et al., , 2016Dallarés et al., , 2017Pérez-i-García et al., 2015b. It could be hypothesized that this may be partly related to the fact that Bythitidae are viviparous (without free larvae exposed to external influences), which limits egg and larval dispersion and thus colonization of different habitats and exposure to a wider array of parasites. ...
... In effect, the relevance of body size for explaining parasite infection patterns is evidenced by Table 3 Developmental stage, location within host, prevalence (P(%)) and mean abundance (MA) ± standard deviation (SD) of parasites recovered in whole specimens and in intestines (BATIMAR project, years 1988 and1989) 0.06 ± 0.14 0.00 ± 0.00 0.00 ± 0.00 0.53 ± 0.08 (0.35-0.65) 0.41 ± 0.24 (0.12-0.93) significant associations found in the present study between this variable and parasite abundance, richness and diversity in C. alleni and M. atlanticum. As the host grows bigger, it is able to consume larger and more diverse prey, which will increase parasite transmission, and may also accumulate parasites (especially larval forms) that "wait" to be trophically transmitted onto their next host (Dallarés et al., 2017). In relation to M. atlanticum, its depauperate parasite community is typical of fish with a more pelagic distribution due to the lower availability of intermediate hosts on the water column (Campbell et al., 1980;Marcogliese, 2002). ...
Article
Deep-sea habitats are home for a variety of yet poorly known fish species, some of which display specialized life strategies, as is the case of Bythitidae and Zoarcidae. With the purpose of elucidating biological and ecological aspects of representatives of these families in NW Mediterranean waters, a large dataset based on 599 specimens of Cataetyx alleni, 30 C. laticeps and 284 Melanostigma atlanticum captured during the last 30 years within the framework of different research projects was used to address their geographical and bathymetric distribution, population structure, reproduction, trophic ecology, parasitism and enzymatic markers in the Balearic basin. Present outcomes revealed a patchy distribution mostly for M. atlanticum, possibly related to aggregation during reproduction and to the association with specific sediments. For the three species, higher densities occurred in the mainland vs. the insular margin, and a diminishing trend in estimated densities over the last decades was observed for C. alleni and M. atlanticum likely linked to climatic oscillations. Trophic data indicated that the two Cataetyx species inhabit the water-sediment interface and mainly feed on suprabenthic prey, while M. atlanticum inhabits the water column near the bottom preying on pelagic organisms and moving towards the seabed during reproduction. These results were supported by the parasitological assessment, which revealed that parasite communities were moderately diverse and abundant for Cataetyx spp. while being highly depauperate for M. atlanticum. Present outcomes confirmed reproduction of C. alleni during autumn-winter and of M. atlanticum during summer. Spawning of the former species may occur in winter-spring, as suggested by the finding, by the first time, of two females captured in March with fully-developed embryos inside. Levels of enzymatic markers quantified in muscle were provided for C. alleni and M. atlanticum for the first time. The special interactions found between the distribution and biology of Bythitidae and Zoarcidae and the sedimentary bottoms that they inhabit indicates that such conventional habitats are more heterogeneous than it is generally assumed and deserve higher attention for future protection.
... Studies regarding the relationships among endoparasites and the diets of their hosts in deep-sea habitats have increased in the last 20 years, mainly in certain geographical areas (Mediterranean sea and North Atlantic) (Klimpel et al., 2006;Busch et al., 2008;Constenla et al., 2015;Dallarés et al., 2017;Pérez-i-García et al., 2017;Woodstock et al., 2020), but for the SEPO this information is rather scarce. These associations are important for elucidating the potential intermediate hosts of endoparasites that infect M. holotrachys and to obtain a better insight of their role in the deep-water communities and food-web of the SEPO. ...
Article
A total of 106 specimens of the big eye grenadier, Macrourus holotrachys, were obtained from 2015 to 2019 as bycatch from the artisanal fishery for Patagonian toothfish (Dissostichus eleginoides) at depths between 1000-2200 m in Northern Chile (app. 22°S 70°W). All individuals were examined for their endoparasite fauna and diets. A total of twenty-five parasite taxa (e.g. fifteen Digenea, six Nematoda, three Cestoda, and one Acanthocephala) were found. Twenty taxa were found as adults, four species were found in the larval stage, and one species was found in both the larval and adult stages. Hysterothylacium sp. (Nematoda); Trypanorhyncha gen. sp. (Cestoda); and Monorchiinae gen. sp. (Digenea) were the predominant species, which had a prevalence of 64.2%, 42.5% and 31.1%, respectively. The diet of M. holotrachys included thirteen item-prey, Decapoda and Ophiuridae showed the highest frequency of occurrence (66.3% and 43.3% respectively). A multivariate canonical correspondence analysis (CCA) showed that the association between endoparasites and diet of M. holotrachys explained 45.1% of the total variance. The detected parasite community consisted of parasites linked to benthic, benthopelagic and pelagic environments. This suggests the role of M. holotrachys as a predator of communities close to the seabed but also within the water column, performing vertical and horizontal migrations in the South Eastern Pacific Ocean.
... Traditionally, pesticides are the stressors most related with the ability to cause damage to the neuromuscular system by inhibiting the activity of ChEs (Richardson et al., 2019), but there are reports of negative correlations between this biomarker and the presence of other stressors (i.e. parasites) (Dallarés et al., 2017). In recent years, increasing evidence have been gathered that pollutants other than pesticides (i.e. ...
Article
Bioindicator species are increasingly valuable in environmental pollution monitoring, and elasmobranch species include many suitable candidates for that role. By measuring contaminants and employing biomarkers of effect in relevant elasmobranch species, scientists may gain important insights about the impacts of pollution in marine ecosystems. This review compiles biomarkers applied in elasmobranchs to assess the effect of pollutants (e.g., metals, persistent organic pollutants, and plastics), and the environmental changes induced by anthropogenic activities (e.g., shifts in marine temperature, pH, and oxygenation). Over 30 biomarkers measured in more than 12 species were examined, including biotransformation biomarkers (e.g., cytochrome P450 1A), oxidative stress-related biomarkers (e.g., superoxide anion, lipid peroxidation, catalase, and vitamins), stress proteins (e.g., heat shock protein 70), reproductive and endocrine biomarkers (e.g., vitellogenin), osmoregulation biomarkers (e.g., trimethylamine N-oxide, Na⁺/K⁺-ATPase, and plasma ions), energetic and neurotoxic biomarkers (e.g., lactate dehydrogenase, lactate, and cholinesterases), and histopathological and morphologic biomarkers (e.g., tissue lesions and gross indices).
... (Cortés, 1999;Fujiwara, Kawato et al., 2021). Previous studies reported that the diets of these two species primarily consist of cephalopods,such as squid, which have been shown to occupy >50% of their stomach content followed by teleost fishes (Carrassón et al., 1992;Cortés, 1999;Dallarés et al., 2017;Ebert, 1994). The consumption of cephalopods likely contributes to their high levels of PBDEs as cephalopods are known for their high levels of PBDEs; a previous study found PBDEs at a concentration of 21-292 ng/g l.w. in the Japanese common squid (Tadarodes pacificus) located in Korean offshore waters (Kim and Stapleton, 2010). ...
Article
Few studies have investigated the prevalence of polybrominated diphenyl ethers (PBDEs) in deep-sea sharks. In this study, the levels and profiles of PBDEs were determined in liver samples of eight different species of deep-sea sharks collected in Suruga Bay, Japan. Widespread contamination of PBDEs in the deep-sea environment was reconfirmed in this study as these persistent organic pollutants (POPs) were detected in all specimens analyzed. Mean ΣPBDE levels in the deep-sea sharks ranged from 7 to 517 ng/g of lipid weight. The distribution patterns of BDE homologues were similar in all species where tetra-BDEs provided the dominant contribution to total PBDEs (46%). PBDEs levels were similar to, or higher than, those seen in other deep-sea sharks from different regions. The levels of PBDEs were likely to reflect their feeding preferences as higher PBDE levels were seen in species with higher trophic positions.
... The habit of blackmouth catsharks to prey mainly on benthopelagic species in all the areas in the Mediterranean and Atlantic Ocean has been confirmed by several studies [104,106,107,[109][110][111][112][113][114]. In most environments, such as the Cantabrian Sea, this is a strategic way to achieve trophic partitioning with other syntopic shark species, such as S. canicula and S. stellaris, which mainly prey on strictly benthic species by using their developed olfactory sense [95]. ...
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Article
Data on the biology and ecology of Galeus melastomus are old/absent for the Southern Tyrrhenian Sea, despite there being numerous studies in the wider area. A total of 127 specimens of G. melastomus from the southern Tyrrhenian Sea, collected in 2018–2019 using trawling nets, were analyzed to investigate size at sexual maturity, sex ratio, length–weight relationships, and feeding habits. To our best knowledge, this is the first time in which all these features were investigated in the Southern Tyrrhenian Sea for G. melastomus. The stomach content analysis showed that G. melastomus had intermediate feeding habits, preying on a great variety of species, especially Cephalopoda, Osteichthyes, and Crustacea. The Levin’s index value (Bi) was 0.53. Sex ratio was 0.92:1, with females slightly more abundant and bigger than males. The results also showed a decrease (33.7 cm for females, 31.1 cm for males) in length at 50% maturity (L50). This could be a result of anthropogenic stressors, such as overfishing and/or and environmental changes, which can induce physiological responses in several species. Our results highlighted the differences related to sexual maturity, growth, and feeding habits of the blackmouth catshark in the studied area, providing reference data to allow comparison with future studies on this species adaptations to this and other deep-sea areas in the Mediterranean Sea.
... Immature G. melastomus specimens are mainly distributed in shallower waters, which appears to be closely related to POC distribution. This different ontogenetic distribution could be attributed to the fact that G. melastomus juveniles, characterized by relatively low swimming capacity, prefer feeding on small prey at the water-sediment interface of the benthic boundary layer (Dallarés et al., 2017). Similarly, female and male Norwegian skate juveniles (distributed at >1100 m) are segregated from the adult/mature population (distributed at 1000-1100 m) probably to avoid predation from other deep-water shark species or to aggregate in areas with suitable prey. ...
Article
This study compiles information on the size distribution and reproductive patterns of five chondrichthyans and 10 bony species dwelling on the continental slope of the Central-Western Mediterranean (south-eastern Sardinian waters, depth 720-1890 m). The abundance of the relatively less numerous chondrichthyans was found to decrease with depth. Almost all chondrichthyan species had a long reproductive period throughout the year at all depths. In bony fishes, the upper bathymetric stratum (<1100 m) was dominated by species with continuous and seasonal (autumn-winter) spawning cycles. At intermediate and lower depths (>1100 m), continuous reproduction was the most common pattern. Both chondrichthyans and bony fishes exhibited large sizes at maturity and at first maturity (>75% and >60% of their maximum body length, respectively), supporting the hypothesis that most deep-sea fish populations are characterized by a delayed maturity, which makes them highly vulnerable to fishing pressure and over-exploitation. In some sharks, population partitioning was observed, according to life stage as a function of depth: adult/mature females occupied deeper habitats than males and juveniles. Conversely, Dipturus nidarosiensis female and male juveniles (>1100 m) were segregated from the adult/mature population, dwelling between 1000 and 1100 m. In four of the 10 bony fishes examined, we found a clear and significant predominance of females, particularly pronounced in Alepocephalus rostratus, which is clearly related to their K-reproductive strategy. The four key-selected species (Galeus melastomus, A. rostratus, Bathypterois mediterraneus and Trachyrincus scabrus), characterized by different reproductive strategies/modal-ities and feeding behaviours, were differently affected by depth and fluxes of organic matter (Particulate Organic Carbon concentration) from the photic zone towards the sea-bottom as a function of sex and life-stage.
... Klimpel et al., 2008Klimpel et al., , 2010Palm and Klimpel, 2008), and the western Mediterranean Sea (e.g. Mateu et al., 2014;Dallarés et al., 2014Dallarés et al., , 2016Dallarés et al., , 2017aDallarés et al., , 2017bConstenla et al., 2015;Pérez-i-García et al., 2015 reflect the increased effort to gain insight in the parasite communities of deep-sea fishes including their use as biological indicators. ...
Article
In the last decades fishing activities have spread from coastal to deeper waters with serious effects on the deep-sea ecosystems and its fauna, which are considered to be highly susceptible to these impacts. The implementation of protection measures is necessary, but the knowledge on this biome is scant, and often limited to species of commercial value. To the best of our knowledge, this study is the first survey to describe and analyse parasite infracommunities of the deep-sea fish Notacanthus bonaparte sampled from three bathymetric strata between the upper and lower slope in the western Mediterranean Sea (Balearic Sea, Spain). The aim of this work was to assess the effect of host specific parameters as well as environmental conditions and spatial and temporal variation on the composition and structure of the parasite communities. We have found poor parasite infracommunities, usually described rather for bathypelagic fishes than observed in fishes with benthic feeding habits such as N. bonaparte, in which two out of five species are considered as accidental infections. The infracommunity composition is determined by the factors, depth and maturity status (size). The dominating taxon, cucullanid larvae, seem to be accumulated throughout the life of the host showing higher abundances in larger fish in deeper waters on the middle and lower slope. The prevalence and abundance of this parasite could be linked to increased water turbidity and it is supposed that these larvae are free-living in the sediment being ingested by N. bonaparte when feeding on benthic organisms. The results suggest that N. bonaparte acts as important intermediate host for this taxon though, the final host is still unknown. The single monogenean species Tinrovia mamaevi was mainly recorded in the upper slope and its higher prevalence in this depth range could be related to higher host densities observed in these depths. The prevalence and abundance of this parasite species could be linked to temperature and salinity, and although measured variations for these parameters were marginal it is supposed that these and probably further additional abiotic factors may influence its distribution pattern. Considering previously published diet data this study indicates potential pathways other than those expected for parasites transmitted via the food web using N. bonaparte as intermediate and definitive host.
... Grillotia sp. is known as a fish parasite from various localities including the Atlantic, Mediterranean, Pacific and Australian waters (Champel and Beveridge 1994;Palm 2004;Dallarés et al. 2017a, b). This parasite species is reported from the Mediterranean waters by different researchers especially from the northwestern Mediterranean Sea (Champel and Beveridge 1994;Genc et al. 2005;Keser et al. 2007;Özer et al. 2014;Dallarés 2016, Dallarés et al. 2017a. There is no report, however, on cestode infection in blackmouth catshark in the Turkish waters. ...
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Blackmouth catshark Galeus melastomus samples were collected using trawl operations from the deep sea area of the Gulf of Antalya, Turkey, in September and October 2016. The present study aims to clarify the status (prevalence and mean intensity) of endo-parasite infection in blackmouth catshark. All parasite specimens were identified as Grillotia sp. Guiart, 1927 (Grillotidae), Trypanorhyncha cestoda. Total length and weight of uninfectedfish (Nui=33) was 30.95 ± 2.06 cm was 26.86 ± 7.56 g, respectively. Total length and weight of infected fish (Ni=7) was 43.63 ± 6.60 cm, 266.22 ± 130.36 g, respectively. Total number of isolated parasite was 363, prevalence 21.67 ± 11.79% and mean intensity 58.50±20.51. This is the first documented report on the occurrence of Grillotia sp. in blackmouth catshark caught in the Gulf of Antalya, Turkey. Marine species diversity in the Mediterranean has increased with the effect of the shipping and transport activities of ornamental fish sector, global warming and also by the migration of non-native species from the Atlantic and Indo-pacific (Bianchi and Morri 2000; Bianchi 2007; Lejeusne et al. 2010). Parasitism, one of symbiotic relationships, can be described as a mode of life of live organisms requiring hosts to survive and reproduce. Parasites damage the tissues on their
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Assessment of fish trophic ecology in natural environments is imperative to understand biological and ecological requirements, supporting the management and conservation of populations and environments. There are several methods available to assess fish diets, generically divided in noninvasive approaches, such as underwater observations, and invasive approaches, such as analyses of lipid biomarkers, stable isotopes and stomach contents. Each one has application assumptions and conditions that must be aligned with study objectives and methodological criteria, assuring results robustness and allowing comparability among different studies. This review addresses the advantages and limitations of these methods, highlighting those applied for stomach analysis (SA). This work presents complete updated review concerning qualitative and quantitative methods applied to SA: sixty equations were reviewed comprising four formulae to value stomachs per se and, for stomach content analysis, eight single indices, fifteen composite indices and thirty-three equations related to modeling approaches. The review presents different potentialities associated to these methods, standardizes distinct names applied to a same method, and provides clarifications on confusion sources due to the use of same names in distinct methods, a source of scientific mistakes detected in the specialized literature.
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The parasite communities of Scyliorhinus canicula and Galeus melastomus are studied for the first time in the Mediterranean. Their seasonal and geographical variations, and their relationship with environmental and fish biological data were tested. The parasite communities of both sharks were characterized by low richness and diversity, and high dominance. Infracommunity structure and composition differed between both species probably due to the consumption of different prey associated with their different bathymetric distributions. For G. melastomus, parasite infracommunity structure and the abundance of some parasites differed across seasons and/or localities due to different dynamics of intermediate hosts populations, in turn linked to different environmental conditions. While Ditrachybothridium macrocephalum was more abundant in juvenile specimens of G. melastomus as a result of ontogenic diet shifts, Grillotia sp. accumulated in adult hosts. The abundance of Proleptus obtusus was significantly higher in S. canicula, likely due to its shallower distribution coupled with higher consumption of reptantian decapods with respect to G. melastomus. Monogenean parasites were associated to high turbidity and temperature levels, which are known to enhance monogenean infection and reproductive success. Cestodes of G. melastomus were linked to high turbidity and O2 levels, which increase zooplankton biomass, favouring the transmission of heteroxenous parasites.
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free software http://www.zoologia.hu/qp/qp.html
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New morphological, molecular and ecological data for Ditrachybothridium macrocephalum Rees, 1959 (Cestoda: Diphyllidea) are presented and discussed based on specimens recovered from the blackmouth catshark Galeus melastomus Rafinesque (Scyliorhinidae) in the Western Mediterranean. A redescription of the plerocercus of this parasite is provided and new data on immature and mature worms including the first description of the eggs are reported, based on light and scanning electron microscopy observations. Analysis of 28S rDNA (domains D1-D3) sequences from plerocerci, immature and adult specimens revealed that they are conspecific with specimens from the North East Atlantic. Although previous authors considered that museum specimens identified as D. macrocephalum may represent more than one species, examination of type- and voucher material revealed no relevant morphological differences between museum specimens and the present material. Information on infection levels of D. macrocephalum is provided from a large number of host specimens (n = 170). This species was more abundant in juvenile than in adult hosts and on the middle slope than on the upper slope; this may be related to ontogenetic and bathymetric diet shifts of G. melastomus.
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Metabolic enzyme activities in red (RM) and white (WM) myotomal muscle and in the heart ventricle (HV) were compared in two lamnid sharks (shortfin mako and salmon shark), the common thresher shark and several other actively swimming shark species. The metabolic enzymes measured were citrate synthase (CS), an index of aerobic capacity, and lactate dehydrogenase (LDH), an index of anaerobic capacity. WM creatine phosphokinase (CPK) activity, an index of rapid ATP production during burst swimming, was also quantified. Enzyme activities in RM, WM and HV were similar in the two lamnid species. Interspecific comparisons of enzyme activities at a common reference temperature (20°C) show no significant differences in RM CS activity but higher CS activity in the WM and HV of the lamnid sharks compared with the other species. For the other enzymes, activities in lamnids overlapped with those of other shark species. Comparison of the HV spongy and compact myocardial layers in mako, salmon and thresher sharks reveals a significantly greater spongy CS activity in all three species but no differences in LDH activity. Adjustment of enzyme activities to in vivo RM and WM temperatures in the endothermic lamnids elevates CS and LDH in both tissues relative to the ectothermic sharks. Thus, through its enhancement of both RM and WM enzyme activity, endothermy may be an important determinant of energy supply for sustained and burst swimming in the lamnids. Although lamnid WM is differentially warmed as a result of RM endothermy, regional differences in WM CS and LDH activities and thermal sensitivities (Q10 values) were not found. The general pattern of the endothermic myotomal and ectothermic HV muscle metabolic enzyme activities in the endothermic lamnids relative to other active, ectothermic sharks parallels the general pattern demonstrated for the endothermic tunas relative to their ectothermic sister species. However, the activities of all enzymes measured are lower in lamnids than in tunas. Relative to lamnids, the presence of lower WM enzyme activities in the thresher shark (which is in the same order as the lamnids, has an RM morphology similar to that of the mako and salmon sharks and may be endothermic) suggests that other factors, such as behavior and swimming pattern, also affect shark myotomal organization and metabolic function.
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Parasites, being an integral part of every ecosystem and trophically transmitted along the food webs, can provide detailed insights into the structure of food webs and can close the information gap between short-term stomach content analyses and long-term fish otolith analyses. They are useful for tracking ontogenetic shifts in the host's diet, the occurrence of specific organisms or migratory behaviour of their hosts, even in inaccessible environments. In the present study, stomach content analyses and parasitological examinations were performed on 70 Atlantic cod Gadus morhua, one of the most important high-level predators of small fish in the North Atlantic, caught during one research vessel cruise from West and East Greenlandic waters. Analyses revealed significant differences in fish size with higher values for East Greenland (average total length (TL) of 50.5 cm) compared to West Greenland (average TL of 33.3 cm). Clear differences were also present in prey and parasite composition. Crustacea was the main food source for all fish (IRI = 10082.70), while the importance of teleosts increased with fish size. With a prevalence of 85 % in West Greenland and 100 % in East Greenland, Nematoda were the most abundant parasite group. The results indicate an ontogenetic shift in the diet, which are discussed in the context of the common distribution theory, stock dynamics and migratory behaviour.
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The present study examined metabolic enzyme activities of 61 species of demersal fishes (331 individuals) trawled from a 3000 m depth range. Citrate synthase, lactate dehydrogenase, malate dehydrogenase, and pyruvate kinase activities were measured as proxies for aerobic and anaerobic activity and metabolic rate. Fishes were classified according to locomotory mode, either benthic or benthopelagic. Fishes with these two locomotory modes were found to exhibit differences in metabolic enzyme activity. This was particularly clear in the overall activity of citrate synthase, which had higher activity in benthopelagic fishes. Confirming earlier, less comprehensive studies, enzyme activities declined with depth in benthopelagic fishes. For the first time, patterns in benthic species could be explored and these fishes also exhibited depth-related declines in enzyme activity, contrary to expectations of the visual interactions hypothesis. Trends were significant when using depth parameters taken from the literature as well as from the present trawl information, suggesting a robust pattern regardless of the depth metric used. Potential explanations for the depth trends are discussed, but clearly metabolic rate does not vary simply as a function of mass and habitat temperature in fishes as shown by the substantial depth-related changes in enzymatic activities.
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The usefulness of fish parasite communities as bioindicators of environmental stress was tested on two benthic fish species, the red mullet (Mullus barbatus) and the spotted flounder (Citharus linguatula), during the spring of 2006 at two sites of the Catalan coast (northwestern Mediterranean): an anthropogenic-impacted area located close to the city of Barcelona, and a less polluted area close to Blanes (Girona). Gonadosomatic and hepatosomatic indices and condition factor were determined for the fishes caught. Prevalence, mean intensity, mean abundance and species richness of the parasites found in the survey were calculated for both species and locations, and the main histological alterations were recorded. Cysts of unknown aetiology and intestinal coccidians were reported only in red mullets from the area close to Barcelona, which were highly parasitized by the digenean Opecoeloides furcatus and the nematode Capillaria sp. However, a higher prevalence of Ichthyophonus sp. was reported in the spotted flounder from Blanes. Cysts of unknown aetiology, some nematodes and Ichthyophonus sp. may be associated with pollution.
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The sixgill shark Hexanchus griseus is a large, active, deep-water species that typically occurs along the outer continental shelves and their upper slopes. Stomach analysis was performed on 137 specimens collected off Namibia and South Africa. The major prey groups were cephalopods, teleosts, chondrichthyans and marine mammals. Dietary changes of sixgill sharks are related to growth. In most of their area of distribution, sixgill sharks have few comparable competitors, because sympatric squaloids and lamnoids of equivalent size feed at a lower trophic level.
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The utility of splenic macrophage aggregates (MAs) as an indicator of fish exposure to degraded environments was evaluated in several species of estuarine fishes as part of the Environmental Protection Agency's Environmental Monitoring and Assessment Program–Estuaries (EMAP-E). Using image analysis, we measured the number and mean size of MAs per square millimeter on tissue sections of spleen from 983 fishes representing seven species from 266 stations scattered across coastal estuaries of the Gulf of Mexico. At 16 stations, at least one fish exhibited a high density of MAs (>40 MAs/mm). Densities of MAs that exceeded 40/mm correlated with exposure to either hypoxic conditions or sediment contamination. Fisher's exact test showed that the observed frequencies of joint occurrence between high numbers of MAs and both high sediment contaminants and low dissolved oxygen were significantly greater than the expected background frequencies. For all 16 sites where MAs were greater than 40/mm, sediments displayed at least one contaminant at a concentration in the highest 5% of those observed for all Gulf of Mexico stations. Additionally, comparison of subjective visual analyses with the image analysis measurements showed a strong correlation, indicating that similar analyses can be performed without computer image analysis. This study demonstrates that splenic MAs are effective biotic indicators for discriminating between fish exposed to degraded and nondegraded environments.
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The impact of fishing on chondrichthyan stocks around the world is currently the focus of considerable international concern. Most chondrichthyan populations are of low productivity relative to teleost fishes, a consequence of their different life-history strategies. This is reflected in the poor record of sustainability of target shark fisheries. Most sharks and some batoids are predators at, or near, the top of marine food webs. The effects of fishing are examined at the single-species level and through trophic interactions. We summarize the status of chondrichthyan fisheries from around the world. Some 50% of the estimated global catch of chondrichthyans is taken as by-catch, does not appear in official fishery statistics, and is almost totally unmanaged. When taken as by-catch, they are often subjected to high fishing mortality directed at teleost target species. Consequently, some skates, sawfish, and deep-water dogfish have been virtually extirpated From large regions. Some chondrichthyans are more resilient to fishing and we examine predictions on the vulnerability of different species based on their life-history and population parameters. At the species level, fishing may alter size structure and population parameters in response to changes in species abundance. We review the evidence for such density-dependent change. Fishing can affect trophic interactions and we examine cases of apparent species replacement and shifts in community composition. Sharks and rays learn to associate trawlers with food and feeding on discards may increase their populations. Using ECOSIM, we make some predictions about the long-term response of ecosystems to fishing on sharks. Three different environments are analysed: a tropical shelf ecosystem in Venezuela, a Hawaiian coral reef ecosystem, and a North Pacific oceanic ecosystem. (C) 2000 International Council for the Exploration of the Sea.
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This study determined baseline health and condition values of Pacific herring Clupea pallasi in 1994 in Prince William Sound (PWS), Alaska. In April 1994, 134 herring were collected from 3 spawning sites in PWS, including a sequential sampling from 1 site. For each herring, morphometric characteristics, sex and presence of gross external and internal lesions were documented, and samples were processed for aging, virological, bacteriological and histological analysis. The study did not reveal trends in herring health and condition in 1994 that could reasonably be attributed to the 'Exxon Valdez' oil spill in 1989. No viruses or pathogenic bacteria were detected, but herring worms, a coccidian parasite and a systemic and virulent fungal infection were found in the herring. The degree of vacuolation in liver cells, previously thought to indicate exposure of fish to oil, varied significantly with the stage of reproductive development of the herring. Similarly, the liver melanomacrophage index, also believed to be correlated with environmental toxicant exposures, varied significantly among sample locations and with collection date. In this study, significant differences in age distribution of spawning herring populations occur in close geographic proximity and collection time intervals in PWS. Based on our results, the use of condition factor, disease and indices of liver function to indicate pollutant exposure are likely to be invalid unless other factors unrelated to pollutant exposure are taken into account, such as reproductive stage of the herring, spawning behavior and location, age of herring and collection date. Thus, we conclude that various hypotheses advanced regarding impacts of the 'Exxon Valdez' oil spill as well as other cases of environmental contamination cannot be supported without rigorous statistical evaluation of natural variations in indices of fish health and condition.
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Bathymetric distribution of Centroscymnus coelolepis has been studied. This species was restricted to the lower slope (1419 to 2251 m), where it was the only abundant shark. Galeus melastomus was abundant below 1000 m but became rare between 1400 and 1600 m, so that there is almost no bathymetric overlap with C. coelolepis. Greatest abundance of G. melastomus in the Catalan Sea was found in the upper slope. Diets of both species showed a very low overlap which is mainly attributed to the dietary specialization of C. coelolepis. Its diet is almost exclusively based on cephalopods. The diet of G. melastomus has been analyzed at depths below 1000 m. Its diet is more diverse than that of C coelolepis and cephalopods are not preferential prey. The upper and middle slope specimens of G. melastomus have a different diet; this difference may be the consequence of a change in available resources. Finally the trophic position of Etmopterus spinax, the third most abundant shark below 1000 m, seems to be more similar to that of C. coelolepis. These results suggest that a possible competition is more likely between C. coelolepis and E. spinax than between C. coelolepis and G. melastomus. This could explain the bathymetric displacement of C coelolepis in the western Mediterranean as a result of an interaction between species of higher trophic levels.
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An extensive survey of the deep-living fishes of the Catalan Sea (western Mediterranean) recorded 31 species in 19 families and 29 genera from 100 samples at depths between 960 and 2251 m. Chlorophthalmidae, Moridae and Macrouridae accounted for nearly 85% of all specimens taken. In biomass terms, Hexanchidae, Moridae, Alepocephalidae and Chlorophthalmidae were the most important families. A quantitative model of the bathymetric distribution of the species is presented. The ‘centre of gravity’ of species’ distribution and the habitat width, a measure of the distribution heterogeneity, are also given. Out of the 31 demersal species caught, the distributions of only 13 are centered below 1000 m. The Mediterranean deep-sea ichthyofauna is very impoverished in comparison with the adjacent Atlantic Basin fauna.
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The present study was undertaken to examine the parasite fauna of spiny dogfish, and to determine seasonal variations in infection rates and faunal composition. A total of 10 metazoan parasite species was recorded, of which four species occurred in the intestine, three species were parasitic on the gills, two species occurred on the skin, and one species parasitized the spiracle. However, a cumulative parasite species richness curve indicated that a larger sample may have yielded additional parasite species. The parasite assemblage consisted of five species of copepods (Eudactylina acanthii Scott, Caligus curtis Müller, Pandarus bicolor Leach, Echthrogaleus coleoptratus (Guerin-Meneville) and Pseudocharopinus bicaudatus (Krøyer)), two species of nematodes (Anisakis simplex Rudolphi and Hysterothylacium aduncum (Rudolphi)), two species of cestodes (Trilocularia gracilis Olssen and Gilguina squali (Fabricius)), and one species of monogenean (Erpocotyle abbreviata (Olssen)). The parasite fauna was found to be similar to that of S. acanthias from the North Sea, and from New Zealand waters. Results obtained during the present study indicate that the infection rates of certain parasite species display seasonal cycles, most species displaying their greatest prevalence in spring and their lowest prevalence in autumn.
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A total of 13 026 fishes belonging to 82 species and 43 families were collected in a continuous transect between depths of 200 and 1800 m south of the Balearic Islands (Algerian basin, western Mediterranean). The analysis of 32 bottom trawls showed the existence of 4 groups associated with the upper slope (groups 1 and 2, from 200 to 400 and 400 to 800 m, respectively), middle slope (group 3, from 800 to 1400 m) and lower slope (group 4, below a depth of 1400 m). The differences in the mean values of the ecological parameters species richness, abundance, biomass and mean fish weight were also indicative of distinctive characteristics between these fish assemblages. Species richness decreased significantly with depth. The highest values of diversity corresponded to the samples from group 2. Biomass did not show any specific trend throughout the whole bathymetric range. Mean fish weight show 2 different trends along the continental slope: a bigger-deeper phenomenon at the upper 1000 to 1200 m depth, and a smaller-deeper phenomenon below this depth. Our results are compared with those obtained in the north Atlantic basin and in the western Mediterranean (Balearic basin), and the main factors affecting these deep-sea fish assemblages are discussed.
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The greater forkbeard Phycis blennoides is a benthopelagic fish distributed in the Mediterranean and NE Atlantic. The main goal of this study is to describe the complete parasite community of this species, which is at present unknown. A total of 188 specimens of P. blennoides were captured in the Balearic Sea (NW Mediterranean Sea) at 550–1,250 m depth during the four seasons of 2007, in summer of 2010 and in summer and autumn of 2011 at five distinct localities off the mainland slope off Catalonia coasts and off the insular slope off the Balearic Islands. Environmental and fish biological, parasitological, dietary, enzymatic and histological data were obtained and the relationships among them tested. A total of 20 different parasites were recovered, of which 11 constitute new host records. The most important parasites were the monogenean Diclidophora phycidis, the digeneans Bathycreadium brayi and Lepidapedon spp., the nematodes Capillaria gracilis, Collarinema collaris, Cucullanus sp. and Hysterothylacium aduncum, and the copepod Clavella alata. Overall, the parasite community of P. blennoides was characterized by high abundance, richness and diversity. Significant differences in the structure of the parasite community were detected between samples from < 1,000 and > 1,000 m depth and between samples from off the mainland and insular slopes. Significant seasonal and/or geographical differences were found for some specific parasites. Abundance of the nematode C. collaris was associated to high levels of turbidity and O2 concentrations near the bottom. Abundances of H. aduncum, D. phycidis, B. brayi and Lepidapedon spp. were linked to high near-bottom temperature and salinity. Dietary analyses evidenced the role as potential intermediate hosts in parasite transmission by some prey (e.g. the teleost Gaidropsarus biscayensis for the cestode Grillotia cf. erinaceus and the nematodes Anisakis spp. or the euphausiid Meganyctiphanes norvegica for the acanthocephalan Echinorhynchus sp.). While the abundance of B. brayi, C. collaris, Cucullanus sp. and Echinorhynchus sp. was negatively linked to acetylcholinesterase activity (AChE), the abundance of Echinorhynchus sp. and H. aduncum correlated positively with lipid peroxidation levels. Cysts of unknown etiology in fish gills were detected at higher prevalence than in any other fish from the same area. Number and area of hepatic macrophage centres varied significantly among seasonal and geographical groups and seemed not significantly influenced by parasite infection levels.
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The family Sphyriocephalidae Pintner, 1913, which comprises the genera Hepatoxylon Bosc, 1811, Sphyriocephalus Pintner, 1913 and Heterosphyriocephalus Palm, 2004, is revised from newly-collected and museum material. Heterosphyriocephalus encarnae n. sp. is described from the pelagic thresher, Alopias pelagicus Nakamura (Lamniformes: Alopiidae) collected from the Pacific Ocean off Boca del Alamo, Mexico. This species can be readily distinguished from the rest of sphyriocephalids by its small size, low number of proglottids and long velum with a characteristically irregular and folded border, among other features. The tentacles show a distinctive basal armature, and a heteroacanthous typical metabasal armature with heteromorphous hooks. Redescriptions are provided for Sphyriocephalus tergestinus Pintner, 1913 and S. viridis (Wagener, 1854) Pintner 1913 based on novel morphological data. A phylogenetic analysis including the available sequences of sphyriocephalid species plus new generated sequences of S. tergestinus has been performed, from which S. tergestinus is allocated into Heterosphyriocephalus as H. tergestinus n. comb. New dichotomous keys for the determination of genera of Sphyriocephalidae are provided, as well as new generic diagnoses for Sphyriocephalus and Heterosphyriocephalus and keys for the determination of species within both genera. Although the morphology of the genus Hepatoxylon is not addressed in the present study, the available sequence of the type-species has been incorporated in the phylogenetic analysis and its relationship to the other two genera of the family is discussed.
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In a sample of 143 blackmouth catsharks. Galeus melastomus caught from off the coast of Languedoc (southern France, northern Mediterranean). 123 specimens were infested by a coccidian. It is a new species belonging to the genus Eimeria (s. I.) Schneider. 1875 sensu Lom and Dykova (1982) and named Eimeria palavensis n. sp. The species was described and its parasitic incidence on G. melastomus is detailed. The coccidian density is relatively high in both sexes, the category of specimens (juvenile or adult) and also slightly related to the reproductive state of the adult females.
Chapter
This chapter reviews the melano-macrophage centers of fish. Macrophages participate in the defense of the organism in a number of ways. They remove debris during tissue involution and repair, they destroy microorganisms by phagocytosis, they may take up and process antigens, they may kill antigenically deviant cells, notably neoplastic cells, and they may actively secrete various substances such as lysozyme and Interferon. While only further research can establish whether fish melano-macrophages are capable of carrying out all these functions, it is obvious that they do execute a multiplicity of functions. At the two extremes, they have been described as being of a lymphoreticular nature and acting as dumps for a wide range of materials. The term dump, however, needs much qualification in the light of the probable recycling of various substances. The centers should be regarded as sites where a variety of materials are aggregated, processed, sifted, and disposed of in a number of ways rather than regarding them as static areas passively accepting and storing any material that comes their way. However, the possibility that the pigments that accumulate in the centers could be broken down and disposed of in some way cannot be discounted.
Article
A histological study was conducted in Mullus barbatus captured from two different zones of the Catalan coast (western Mediterranean): 1. a polluted site (near Barcelona) and 2. a less contaminated zone (Creus Cape). No histopathological alterations were found in any of the organs studied. An image analysis study was carried out on splenic sections in order to quantify the number and area of melano-macrophage centres (MMC). The area of MMC was significantly greater in fish sampled from the polluted area indicating that MMC centres in Mullus barbatus could be useful to monitor environmental degradation in NW Mediterranean.
Article
Parasite communities of three abundant benthopelagic macrourid species (Hymenocephalus italicus, Nezumia aequalis and Trachyrincus scabrus) of the upper slope from the western Mediterranean were analysed seasonally. Histopathological, dietary and environmental information (temperature, salinity, O2 and turbidity) were also obtained. The three fish hosts shared only three parasite species (the nematodes Raphidascaris macrouri and Hysterothylacium aduncum and the acanthocephalan Echinorhynchus trachyrinci). H. italicus, the most benthopelagic fish, showed low parasite richness and diversity. The highest total mean abundance of parasites was found in spring for H. italicus and T. scabrus, coinciding with the highest prevalence/abundance of the majority of parasites whereas parasites of N. aequalis exhibited the highest richness, mean abundance and diversity in winter. Parasites related with benthic or infaunal preys were linked to autumn and summer samples off Besós (Barcelona). Some parasites were also linked to high turbidity, which may be due to higher abundances of the intermediate hosts, such as near-bottom zooplaktonic or suprabenthic preys. Few histopathological alterations (e.g. cysts of unknown aetiology) were observed restricted to the two most benthic-feeding fish species inhabiting more closely the near-bottom/sediment level, especially in autumn.
Thesis
Little is known about deep-sea Arctic fish communities, especially relating to species distributions, basic biology and ecology. Surveys usually focus on commercially exploitable species such as Greenland halibut (Reinhardtius hippoglossoides) and shrimp (Pandalus sp.). Most community studies on Arctic food web dynamics often overlook underlying patterns such as shifting trophic position with environmental change. This is the first study that describes the fish/invertebrate food web of the deep-sea Arctic in terms of predator-prey and host-parasite relationships. The objectives of this thesis were to determine factors that affect community dynamics and trophic relationships within deep-sea fish communities of the Davis Strait and Baffin Bay and involved 1) recognizing broad feeding patterns by combining fish groups, regardless of phylogenetic relationships, by size and/or age class as well as similar ecologies, 2) determining factors that affect community dynamics and trophic relationships in benthic Arctic marine communities and 3) assessing the trophic position of individual species based on stomach content analysis, parasite assemblages and stable isotope data. Four hypotheses were generated, involving fish community composition with changing environmental variables, the effectiveness of trophic guilds in the construction of deep-sea Arctic food webs, the value of using parasites and stable isotopes in combination with stomach content analysis, and the role of size and age class in determining trophic position. Results illustrated that species within this region are distributed along one or more environmental gradients such as latitude, longitude, temperature and depth, resulting in continually shifting species composition throughout the system. Traditional methods of trophic evaluation, namely guild determination and food web construction, were not appropriate for deep-sea Arctic communities due to the prevalence of generalist feeding throughout. These results contrast with previous reports on tropical or temperate marine environments in which fish species can be separated into clear trophic levels based on similar data. A multivariate approach combining stomach contents and endohelminths demonstrated that habitat utilization and diet best described trophic relationships within the region; fish species were divided into trophic ‘groups’ based on their ability to utilize benthic and pelagic zones. This thesis provides, for the first time, an analysis of endohelminth communities of deep-sea species that supports dietary information. Data from parasite infracommunities revealed that, at best, it can be used to describe the preferred habitat zone of individual fish species without stomach content analysis and, at the very least, it gives strong support to diet data. Due to the broad overlap of diet preferences, tissue values of δ13C and δ15N stable isotopes were not as useful to describe trophic position as these values were unable to clearly designate a species to trophic position. However, the use of differences in δ13C and δ15N values were able to reveal similar patterns of habitat utilization and feeding strategies to those seen for diet and parasite analyses. No significant relationship was found between fish size and stable isotope signature, indicating that the diets of different fish size classes overlap and/or prey species contain similar isotopic signatures in the deep-sea. This study has provided Arctic science with the first insights into community dynamics within deep-sea Arctic habitats. Hopefully, better decisions will be possible regarding the health and structural integrity of marine Arctic communities in the face of environmental change. Marine resource managers can no longer consider single-species populations when assessing the health of marine communities as the data from this thesis clearly show a marine system in which the life histories of its species are inextricably intertwined. Clearly for the future, disturbances such as single or multiple species overfishing and/or global warming must be considered in the context of the National Marine Fisheries Policy of ‘Ecosystem-Based Management’.
Article
This study examines the parasite communities of Alepocephalus rostratus and its influence on some fish biochemical markers and histological alterations. Alepocephalus rostratus constitutes the second most important fish species, in terms of biomass, inhabiting the deep slope of the Catalan Sea (Balearic Sea, NW Mediterranean). The study revealed eight different parasite species in this host: one coccidian, one digenean, one monogenean, one cestode and four nematodes. The parasite fauna of A. rostratus was partially dominated by larval forms (four of the seven metazoan taxa found), which combined with low species richness corresponds to a parasite fauna pattern more typical of bathypelagic fish species rather than demersal ones. The larval tetraphyllideans and cucullanid nematodes were the predominant species. In relation to depth, differences in abundance of the nematodes Cucullaninae gen. sp. and Hysterothylacium aduncum were found, probably due to the dietary shift in the fish host at greater depth. Thus, Cucullaninae gen. sp. and H. aduncum could be regarded as indicators for discriminating populations of A. rostratus in relation to depth in NW Mediterranean waters. Of the biochemical markers examined, acetylcholinesterase (AChE) and lactate dehydrogenase (LDH) activities and lipid peroxidation (LP) levels, only LP showed significant differences between depths. A positive relationship was found between AChE activity and Tetraphyllidea fam. gen. sp., Anisakis physeteris and H. aduncum abundance and a negative one with the abundance of Cucullaninae gen. sp. LDH showed a positive relationship with the abundance of the parasites Paracyclocotyla cherbonnieri and Tetraphyllidea fam. gen. sp. At cito-histological level, coccidians were detected in the pyloric caeca with a prevalence of 90% in Barcelona, but in the rest of organs almost no alterations were detected. The restricted macroplanktonic diet of A. rostratus, that maintains it distant from the sea-floor for longer periods than other demersal species, probably makes this species less susceptible to sediment- associated impacts including parasitism.
Article
By combining an examination of stomach contents yielding a snapshot of the most recent trophic niche and the structure of parasite communities reflecting a long-term feeding niche, this study aimed at gaining more comprehensive information on the role of the small-sized deep-water velvet belly lantern shark Etmopterus spinax in the local food webs of the Galicia Bank and the canyon and valley system of the Avilés Canyon, which have been both proposed for inclusion in the Natura 2000 network of protected areas. As far as is known, this study provides the first comparative parasite infracommunity data for a deep-sea shark species. Component parasite communities in E. spinax were relatively rich, whereas the infracommunities were rather depauperate, with similar low diversity at both localities. The significant differences in the composition and structure of both parasite communities and prey assemblages indicate differential effects of the two deep-sea ecosystems on both long-term and most recent trophic niches of E. spinax. These results underline the importance of the use of multivariate analyses for the assessment of geographical variation in shark populations based on parasites and diet data.
Article
A major obstacle to the investigation of deep-sea biology is the lack of instrumentation to retrieve deep-sea organisms from their habitat alive, particularly fishes with physoclistous swimbladders. To perform physiological experiments on deep-sea fishes under in situ but controlled conditions, we constructed a high-pressure fish trap-respirometer to capture deep-water fishes at depth and return them to the surface alive at in situ pressure and temperature. Pumps and instrumentation connected aboard ship or in the laboratory are used for maintenance of the animal and experimentation. The trap was designed so that respiration rates, pressure tolerance, and metabolic responses to various gas concentrations (CO2 and O2) could be examined in a controlled environment. The trap is deployed as an autonomous lander or free vehicle to depths of 4000 m. Once on the seafloor, a fish is captured on a baited hook that triggers the reeling of the fish into the pressure vessel and closure of its sealing door. Two fish, Coryphaenoides acrolepis, have been recovered live from 1450 m and maintained in the laboratory. Both fish were retrieved at ∼95% of their in situ pressure and at temperatures of ∼6°C. Oxygen consumption rates of these fish were 54.99 μmol O2 kg-1 h-1 (1.158 kg, 65.0 cm total length, 23.5 cm pre-anal fin length) and 79.43 μmol O2, kg-1 h-1 (1.305 kg, 66.5 cm total length, 24.5 cm pre-anal fin length). The latter fish was maintained for 3.5 d, and it survived gradual decompression to 76% of the pressure at its capture depth. © 2005, by the American Society of Limnology and Oceanography, Inc.
Article
This study examined the population structure, reproductive cycle and feeding pattern of the lanternfih Lampanyctus crocodilus in the Balearic Basin (NW Mediterranean) from 450 to 1800 m of depth and at a seasonal scale. Juveniles were mainly located at shallower depths, but also at deepest stations in autumn, while adults mostly inhabited intermediate depths with their centre of gravity (CoG) located at 800-1000 m of depth. Migrations of adults to deeper depths were detected in late summer-autumn, probably linked to the occurrence of nepheloid layers at ca. 1200 m, which in turn enhance the biomass of zooplankton, prey for L. crocodilus. Diet was mainly based on euphausiids and mysids with marked seasonal variations both on the upper (US=450-800 m) and lower (LS=1000-1800 m) slopes, where suprabenthic gammariids and pelagic decapods were also dominant. Fullness increased from winter to autumn on the US, while it had a maximum in spring on the LS, in parallel with high consumption of gelatinous zooplankton, which is probably more available after the phytoplankton bloom in late winter. Reproduction occurred in winter, confirmed by the higher percentage of mature females and high gonadosomatic indices (IG) at both depth ranges. Hepatosomatic index (IH) showed an inverse trend to IG on the US, except in autumn, and was almost parallel on the LS, probably attributable to the migration of adults, which determined different temporal schemes in energy use and storage for reproduction on the US vs. LS. Consistent with the different patterns observed at the two depth ranges, environmental drivers of fullness (i.e. feeding intensity) and IG (as a proxy of reproductive cycle) differed on the US and LS. Biomass of mysids and euphausiids were the most explanatory variables of fullness on the US and LS respectively, pointing to increasing feeding intensity when a resource was more available. IH also explained fullness, suggesting that greater feeding intensity in pre-reproductive periods enabled energy storage in the liver. IG was linked directly (i.e. mysids) or indirectly (i.e. surface primary production recorded 2 months before sampling) to food availability, implying a rapid response to vertical food inputs by deep-sea predators. Also IG in L. crocodilus was related to population density, which suggests aggregations for reproduction. Estimates of L. crocodilus trophic levels, and of other accompanying mesopelagic fishes, indicated that species feed through a continuum spanning the third trophic level, confirming the key role of mesopelagic fishes in transferring organic carbon between trophic levels. Trophic niche segregation among mesopelagic species was pronounced and non-overlapping groups could be distinguished due to different vertical distribution and/or migratory behaviour. The study highlights the important role of the Benthic Boundary Layer in sustaining benthopelagic communities in the deep Mediterranean and the essential requirement to study the biology of a species throughout the whole depth range it inhabits and not just at exploited depths (i.e. fishing grounds).
Article
Organisms inhabiting submarine canyons can be potentially exposed to higher inputs of anthropogenic chemicals than their counterparts from the adjacent areas. To find out to what extend this observation applies to a NW Mediterranean canyon (i.e. Blanes canyon) off the Catalan coast, four deep-sea fish species were collected from inside the canyon (BC) and the adjacent open slope (OS). The selected species were: Alepocephalus rostratus, Lepidion lepidion, Coelorinchus mediterraneus and Bathypterois mediterraneus. Prior to the choice of an adequate sentinel species, the natural variation of the selected parameters (biomarkers) in relation to factors such as size, sex, sampling depth and seasonality need to be characterised. In this study, the activities of cholinesterases (ChEs) and lactate dehydrogenase (LDH) enzymes were determined in the muscle of the four deep-sea fish. Of all ChEs, acetylcholinesterase (AChE) activity was dominant and selected for further monitoring. Overall, AChE activity exhibited a significant relationship with fish size whereas LDH activity was mostly dependent on the sex and gonadal development status, although in a species-dependent manner. The seasonal variability of LDH activity was more marked than for AChE activity, and inside-outside canyon (BC-OS) differences were not consistent in all contrasted fish species, and in fact they were more dependent on biological traits. Thus, they did not suggest a differential stress condition between sites inside and outside the canyon.
Article
The majority of our knowledge on marine tapeworms (cestodes) is limited to taxa that are relatively easy to obtain (i.e., those that parasitize shallower-water species). The invitation to participate in a deep-water research survey off the Condor seamount in the Azores offered the opportunity to gain information regarding parasites of the less often studied sharks of the mesopelagic and bathypelagic zone. All tapeworms (Platyhelminthes: Cestoda) found parasitizing the spiral intestine of squaliform shark species (Elasmobranchii: Squaliformes) encountered as part of this survey, as well as some additional Azorean sampling from previous years obtained from local fishermen are reported. In total, 112 shark specimens of 12 species of squaliform sharks representing 4 different families from depths ranging between 400 and 1290 m were examined. Cestodes were found in the spiral intestines from 11 of the 12 squaliform species examined: Deania calcea, D. cf. profundorum, D. profundorum, Etmopterus princeps, E. pusillus, E. spinax, Centroscyllium fabricii, Centroscymnus coelolepis, C. cryptacanthus, C. crepidater, and Dalatias licha. No cestodes were found in the spiral intestines of Centrophorus squamosus. Light microscopy and scanning electron microscopy revealed several potentially novel trypanorhynch and biloculated tetraphyllidean species. Aporhynchid and gilquiniid trypanorhynchs dominated the adult cestode fauna of Etmopterus and Deania host species, respectively, while larval phyllobothriids were found across several host genera, including, Deania, Centroscyllium, and Centroscymnus. These results corroborate previous findings that deep-water cestode faunas are relatively depauperate and consist primarily of trypanorhynchs of the families Gilquiniidae and Aporhynchidae and larval tetraphyllideans. A subset of specimens of most cestode species was preserved in ethanol for future molecular analysis to allow more definitive determinations of the identification of the larval tetraphyllideans and trypanorhynchs lacking evaginated tentacles and other key diagnostic features.
Article
Parasite communities tend to be dissimilar in hosts that are geographically, phylogenetically, ecologically and developmentally distant from one another. The decay of community similarity is a powerful and increasingly common method of studying parasite beta diversity, but most studies have examined only a single type of distance. Here, we evaluate distances based on the phylogeny, ecology, spatial proximity and size of hosts, as predictors of the similarity of parasite communities in individual hosts, host populations and host species. We surveyed parasites in six species of fish collected simultaneously from six localities in the St. Lawrence River, Canada, and species in a common group of larval parasites were discriminated using DNA sequences from barcode region of cytochrome c oxidase I. Distances based on the habitat use patterns of host species were good predictors of short-term, ecological similarity of parasite communities, such as that operating at the scale of the individual host. The genetic distance between host species was associated with almost all types of similarity at all scales, particularly qualitative and phylogenetic similarity of parasite communities at the level of populations and meta-populations of hosts. The trophic level, diet, spatial proximity and size of hosts were poor predictors of parasite community similarity. The increased taxonomic resolution provided by molecular data increased the explanatory power of regression models, and different factors were implicated when parasite species were distinguished with DNA barcodes than when larval parasites were lumped into morphospecies, as is commonly practiced.
Article
Macrophage aggregates (MAs) are structures in the spleen, kidney and sometimes liver of fishes which have various functions such as recycling/storing/detoxification of cellular wastes and exogenous substances. They have been also reported to be important in the specific immune response and are used as health indicators. Changes in MA density, size and pigment content have been used in national and local monitoring programs in the U.S. as indicators of contaminant exposure. However, MA number and structure can also be affected by other factors, including general stress or nutritional status of fish. An experiment was conducted to study the effects of vitamin E and n−3 highly unsaturated fatty acid (HUFA) deficiencies and stocking density on spleen and kidney MAs of gilthead seabream, one of the most important species for Mediterranean aquaculture. Fish were held at two stocking densities, high and low, and fed experimental diets. Diet NE had no supplemental vitamin E, Diet NFA was deficient in n−3 HUFA and Diet C was a control diet. Number, size and shape factor of MAs were measured using image analysis. The percentage of tissue occupied by MAs was calculated from these measurements. The results showed that high stocking density alone increased the number of splenic but not kidney MAs of fish fed the control diet. A deficiency of n−3 HUFA alone also increased the number of splenic but not kidney MAs at both stocking densities. Vitamin E deficiency alone had no significant effect on MAs in either organ. However, the combined effect of vitamin E deficiency and high stocking density increased the number and size of kidney but not splenic MAs. This study indicates that specific dietary deficiencies can influence MA accumulation and that splenic MAs may be more responsive to general stress than kidney MAs.
Article
Gravid Hysterothylacium aduncum from the intestine of eelpout, Zoarces viviparus, were used as the source of eggs for study. The two first moults occurred in the egg, which does not normally hatch spontaneously. The third-stage larva within the egg was not infective to either fishes or non-crustacean invertebrates, but developed into a typical third-stage larva in Acartia tonsa, harpacticoid copepods, various amphipods, isopods, and mysids. Further development in the fish host was apparently dependent only on the length of the larva. Thus, larvae from harpacticoids (< 1 mm long) and larvae less than 1.5-2.0 mm long from other crustaceans did not survive in the fish; larvae between about 2 and 3 mm in length remained as third-stage larvae in the fish. Larvae longer than 3 mm moulted into fourth-stage larvae in the intestinal lumen of the fish. Thus, a two-host cycle occurs when fishes ingest crustaceans harbouring third-stage larvae longer than 3 mm, and a cycle of three (or more) hosts when fishes ingest third-stage larvae less than 3 mm long. Ctenophores, chaetognaths, polychaetes, and ophiuroids, which become infected by ingesting infected crustaceans, may act as obligate intermediate hosts or trans-port hosts.
Article
This study compares the acetylcholinesterase (AChE) activity of herring Clupea harengus infected with Anisakis simplex larvae and non-infected individuals caught in coastal waters of the southern Baltic. Acetylcholinesterase activity was measured spectrophotometrically. Generalized linear models were applied to analyse the dependence of AChE activity on the area of sampling and the biological parameters of fish and their parasites. The AChE activity of herring was higher in samples from the western and central coasts (regarded as "clean" waters) than in fish caught in the semi-enclosed areas of the Gulf of Gdańsk and Vistula Lagoon (regarded as "polluted" sites). The opposite relationship was noted in the activity of AChE extracted from A. simplex larvae. In male hosts, the parasitic AChE activity was markedly higher than in the females in all examined areas. © 2005 International Council for the Exploration of the Sea. Published by Elsevier Ltd. All rights reserved.
Article
The shark species, blackmouth catshark (Galeus melastomus), velvet belly (Etmopterus spinax) and coastal spotted dogfish (Scyliorhinus canicula) are an important by-catch of the Balearic Islands (Western Mediterranean) trawl fishery. The catch compositions of the fishery taking these species is described and analysed in terms of landings and discards. Only two of these species are sufficiently abundant to be recorded in the landings (blackmouth catshark and spotted dogfish). The length compositions in terms of both landings and discards were analysed for these two species. Spotted dogfish catches reached similar proportions to those of the target species in the coastal fishery (red and striped red mullet) and in the shelf trawl fishery (European hake); whereas the catches of blackmouth catshark and velvet belly were a small proportion of the total catch in the slope fishery for red shrimp. The size range of the spotted dogfish was between 7 and 53cm TL. Juveniles and adults were distributed throughout the whole area, although adults appeared to be more abundant in the coastal zone. The length distribution of blackmouth catshark showed a trend of increasing size with depth; the size range was between 9 and 63cm TL. For both species, individuals smaller than 35cm TL were usually discarded. Only 25% by number and 60% by weight of the total spotted dogfish catch was landed. For the total blackmouth catshark catch, the corresponding percentages were 10% by number and 35% by weight. The role of these species as indicators of fishing pressure was investigated, taking into account the differences between the two fishing zones sampled, one with a fleet of 24 trawlers and the other with only 4.
Article
This study investigated monogenetic trematode infestation of the gills and gill pathology of yellow­ fin mojarra, Gerres cinereWl (Gerreidae); gray snapper, LutjanWl griseWl (Lutjanidae); and timucu (needlefish), Strongylura timucu (Belonidae) in relation to water quality in south Biscayne Bay, Florida. Two habitats of the three species in the bay, one in the southeast and the other in the south­ west, differed in water quality whereas physical and environmental parameters were similar. The water in southwest Biscayne Bay contained.high amounts of aItlmonia, trace metals, and pesticides which were not present in the southeast bay. The gills of hosts from the habitat with inferior water quality were heavily infested with the Monogenea (Platyhelminthes) Neodiplectanumwenningeri (on G. cinereWl), AncyrocephalWlsp. (on L. griseWl), and AncyrocephalWlparvus (on S. timueu) and suffered from excessive mucus secretion, epithelial hyperplasia, fusion of gill lamellae, clubbing and fusion of filaments, and aneurisms. Only light infestations and little or no abnormal tissue changes were noted in fish from the area of good water quality. The findings led to the conclusion that the pollutants in the water acted as an irritant, stressing the fi$, and producing physical and physiological changes which reduced resistance to infestation by Monogenea. Manmade pollution of coastal waters of south­ east Florida has reached a critical level in the most populated areas, causing substantial envi­ ronmental degradation (Carter 1974) and the loss of valuable fishing grounds, and making some areas unsuitable for recreation. In recent years, the pollution of Biscayne Bay, Fla. (Fig. 1) has become a major issue. The shore of north Bis­ cayne Bay is bordered by Miami and Miami Beach, and lined by bulkheads. It receives a large amount of runoff water from the metropol­ itan areas (Waite 1976). Although the south­ western part of the bay still retains much of its natural shoreline and mangrove forests, it is broken by drainage canals intended to lower the water level in neighboring agricultural and ur­ ban areas. These canals therefore carry agricul­ tural, industrial, and urban wastes into that part of the bay (Waite 1976). The southeastern shore­ line of Biscayne Bay is formed by a chain of islands which is part of Biscayne National Park with no major direct sources of water pollution. The purpose of this study was to investigate if differences existed in the ectoparasite fauna and possible gill pathology in the same three species of fish living in southwest Biscayne Bay in the
Article
The trophic ecology of a midwater fish assemblage was investigated in the eastern Gulf of Mexico, a regime exhibiting the principal physical-biological characteristics of oligotrophic low latitude ecosystems. In all, the diets of 164 species of midwater fishes were examined, with data for 121 being sufficient for analytical comparisons. Cluster analysis grouped the assemblage into 15 feeding guilds, with these falling into two major groups, those including zooplanktivores with largely crustacean diets, and those including predators on large prey, most of which were piscivores. Among the zooplanktivores, the principal predators were the Myctophidae, Sternoptychidae and Gonostomatidae which, respectively, consumed 31%, 27% and 14% of the food biomass eaten daily by the midwater fish assemblage. The myctophids alone accounted for 53% of the copepod and 40% of the euphausiid biomass ingested. The copepod genus Pleuromamma was especially important forage, constituting 40% of the copepod biomass consumed by the midwater fish assemblage. The Stomiidae were the dominant piscivores and accounted for 20% of the total food ingested daily and 61% of the fish eaten, with the majority of their prey being myctophids. Literature comparisons reveal that diet patterns for the eastern Gulf midwater assemblage closely resemble those for mid- to- low latitude oligotrophic regimes in general.
Article
A new species of Grillotia, G. gastrica n. sp., is described from the stomach musculature of the teleosts Upeneichthys lineatus (Bloch & Schneider) and Sillaginodes punctatus (Cuvier) from off Perth, Western Australia. The new species most closely resembles G. pristiophori Beveridge & Campbell, 2001 in having six hooks in each principal row of the metabasal tentacular armature but differs in having a smooth scolex tegument and in having a band of hooklets running the entire length of the external surface of the tentacle rather than diminishing in width to a single hooklet as occurs in G. pristiophori. Grillotia heptanchi (Vaullegeard, 1899) is redescribed and the details of the mature segment are described for the first time. Grillotia adenoplusius (Pintner, 1903) is redescribed from the type-specimens and is considered to be the larval stage of G. acanthoscolex Rees, 1944 (syns G. spinosissima Dollfus, 1969 and G. microthrix Dollfus, 1969). The adult of G. adenoplusius is also redescribed based on the types of G. spinosissima. The type-specimens of G. dolichocephala Guiart, 1935 and G. minor Guiart, 1935 were re-examined and G. minor is considered to be a synonym of G. dolichocephala as is G. meteori Palm & Schröder, 2001. Based on an examination of the type-specimens, G. scolecina (Rudolphi, 1819) is treated as a species inquirenda. A list is provided of the species currently placed in Grillotia.
Article
The influence of mesoscale physical and trophic variables on deep-sea megafauna, a scale of variation often neglected in deep-sea studies, is crucial for understanding their role in the ecosystem. Drivers of megafaunal assemblage composition and biomass distribution have been investigated in two contrasting areas of the Balearic basin in the NW Mediterranean: on the mainland slope (Catalonian coasts) and on the insular slope (North of Mallorca, Balearic Islands). An experimental bottom trawl survey was carried out during summer 2010, at stations in both sub-areas located between 450 and 2200 m water depth. Environmental data were collected simultaneously: near-bottom physical parameters, and the elemental and isotopic composition of sediments. Initially, data were analysed along the whole depth gradient, and then assemblages from the two areas were compared. Analysis of the trawls showed the existence of one group associated with the upper slope (US=450–690 m), another with the middle slope (MS=1000–1300 m) and a third with the lower slope (LS=1400–2200 m). Also, significant differences in the assemblage composition were found between mainland and insular slopes at MS. Dominance by different species was evident when the two areas were compared by SIMPER analysis. The greatest fish biomass was recorded in both areas at 1000–1300 m, a zone linked to minimum temperature and maximum O2 concentration on the bottom. Near the mainland, fish assemblages were best explained (43% of total variance, DISTLM analysis) by prey availability (gelatinous zooplankton biomass). On the insular slope, trophic webs seemed less complex and were based on vertical input of surface primary production. Decapods, which reached their highest biomass values on the upper slope, were correlated with salinity and temperature in both the areas. However, while hydrographic conditions (temperature and salinity) seemed to be the most important variables over the insular slope, resource availability (gelatinous zooplankton and Calocaris macandreae) predominated and explained 59% of decapod assemblage variation over the mainland slope. Both fish and decapods were linked to net primary production recorded over the mainland 3 months before sampling, while the delay between the input of food from the surface and fish abundance was only 1 month on the insular slope. Our results suggest that trophic relationships over insular slopes probably involve a shorter food chain than over mainland slopes and one that is likely more efficient in terms of energy transfer.