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Intra-colonial genetic variability (IGV), the presence of more than one genotype in a single colony, has been increasingly studied in scleractinians, revealing its high prevalence. Several studies hypothesised that IGV brings benefits, but few have investigated its roles from a genetic perspective. Here, using genomic data (SNPs), we investigated these potential benefits in populations of the coral Pocillopora acuta from Reunion Island (southwestern Indian Ocean). As the detection of IGV depends on sequencing and bioinformatics errors, we first explored the impact of the bioinformatics pipeline on its detection. Then, SNPs and genes variable within colonies were characterised. While most of the tested bioinformatics parameters did not significantly impact the detection of IGV, filtering on genotype depth of coverage strongly improved its detection by reducing genotyping errors. Mosaicism and chimerism, the two processes leading to IGV (the first through somatic mutations, the second through fusion of distinct organisms), were found in 7% and 12% of the colonies, respectively. Both processes led to several intra-colonial allelic differences, but most were non-coding or silent. However, 7% of the differences were non-silent and found in genes involved in a high diversity of biological processes, some of which were directly linked to responses to environmental stresses. IGV, therefore, appears as a source of genetic diversity and genetic plasticity, increasing the adaptive potential of colonies. Such benefits undoubtedly play an important role in the maintenance and the evolution of scleractinian populations and appear crucial for the future of coral reefs in the context of ongoing global changes.
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Antozoários , Animais , Antozoários/genética , Recifes de Corais , Genótipo , Genoma/genética , GenômicaRESUMO
With the advent of genomics, sequencing thousands of loci from hundreds of individuals now appears feasible at reasonable costs, allowing complex phylogenies to be resolved. This is particularly relevant for cnidarians, for which insufficient data is available due to the small number of currently available markers and obscures species boundaries. Difficulties in inferring gene trees and morphological incongruences further blur the study and conservation of these organisms. Yet, can genomics alone be used to delimit species? Here, focusing on the coral genus Pocillopora, whose colonies play key roles in Indo-Pacific reef ecosystems but have challenged taxonomists for decades, we explored and discussed the usefulness of multiple criteria (genetics, morphology, biogeography and symbiosis ecology) to delimit species of this genus. Phylogenetic inferences, clustering approaches and species delimitation methods based on genome-wide single-nucleotide polymorphisms (SNP) were first used to resolve Pocillopora phylogeny and propose genomic species hypotheses from 356 colonies sampled across the Indo-Pacific (western Indian Ocean, tropical southwestern Pacific and south-east Polynesia). These species hypotheses were then compared to other lines of evidence based on genetic, morphology, biogeography and symbiont associations. Out of 21 species hypotheses delimited by genomics, 13 were strongly supported by all approaches, while six could represent either undescribed species or nominal species that have been synonymised incorrectly. Altogether, our results support (1) the obsolescence of macromorphology (i.e., overall colony and branches shape) but the relevance of micromorphology (i.e., corallite structures) to refine Pocillopora species boundaries, (2) the relevance of the mtORF (coupled with other markers in some cases) as a diagnostic marker of most species, (3) the requirement of molecular identification when species identity of colonies is absolutely necessary to interpret results, as morphology can blur species identification in the field, and (4) the need for a taxonomic revision of the genus Pocillopora. These results give new insights into the usefulness of multiple criteria for resolving Pocillopora, and more widely, scleractinian species boundaries, and will ultimately contribute to the taxonomic revision of this genus and the conservation of its species.
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Antozoários , Animais , Ecossistema , Filogenia , Genômica , PolinésiaRESUMO
The Bull Shark (Carcharhinus leucas) faces varying levels of exploitation around the world due to its coastal distribution. Information regarding population connectivity is crucial to evaluate its conservation status and local fishing impacts. In this study, we sampled 922 putative Bull Sharks from 19 locations in the first global assessment of population structure of this cosmopolitan species. Using a recently developed DNA-capture approach (DArTcap), samples were genotyped for 3400 nuclear markers. Additionally, full mitochondrial genomes of 384 Indo-Pacific samples were sequenced. Reproductive isolation was found between and across ocean basins (eastern Pacific, western Atlantic, eastern Atlantic, Indo-West Pacific) with distinct island populations in Japan and Fiji. Bull Sharks appear to maintain gene flow using shallow coastal waters as dispersal corridors, whereas large oceanic distances and historical land-bridges act as barriers. Females tend to return to the same area for reproduction, making them more susceptible to local threats and an important focus for management actions. Given these behaviors, the exploitation of Bull Sharks from insular populations, such as Japan and Fiji, may instigate local decline that cannot readily be replenished by immigration, which can in turn affect ecosystem dynamics and functions. These data also supported the development of a genetic panel to ascertain the population of origin, which will be useful in monitoring the trade of fisheries products and assessing population-level impacts of this harvest.
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BACKGROUND: Holothuria (Halodeima) atra Jaeger, 1833 is a tropical sea cucumber usually harvested for the "bêche-de-mer" trade market. It has been reported to reproduce both sexually, through gamete spawning, or asexually, through fission. To date, no study has ever investigated clonality, nor genetic connectivity, among its populations, using microsatellite markers. METHODS AND RESULTS: We isolated the first 21 microsatellite loci specific for H. atra, which were then used to investigate clonal diversity, genetic structure and diversity among 44 H. atra individuals sampled in Reunion Island (southwestern Indian Ocean), over two seasons. All 21 loci were polymorphic, with number of alleles per locus ranging from 2 to 10. No repetitive multi-locus genotype (MLG) and few clonal lineages (MLL) were found. Observed heterozygosities per locus and season ranged from 0.000 to 0.909, while expected heterozygosities ranged from 0.290 to 0.882. Four loci were at Hardy-Weinberg equilibrium for both seasons, all others presenting a deficit of heterozygotes in one or both seasons. Meanwhile, no genetic differentiation was detected between seasons, according to assignment tests and global FST. CONCLUSIONS: These results suggest low asexual propagation in this population. These loci represent useful tools to better understand reproductive strategies and population connectivity of H. atra, and thus provide relevant knowledge for efficient management.
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Holothuria , Pepinos-do-Mar , Animais , Humanos , Equinodermos/genética , Holothuria/genética , Oceano Índico , Repetições de Microssatélites/genética , Polimorfismo Genético , Reunião , Pepinos-do-Mar/genética , Reprodução Assexuada/genética , Reprodução/genéticaRESUMO
BACKGROUND: The tiger shark (Galeocerdo cuvier) is a large iconic marine predator inhabiting worldwide tropical and subtropical waters. So far, only mitochondrial markers and microsatellites studies have investigated its worldwide historical demography with inconclusive outcomes. Here, we assessed for the first time the genomic variability of tiger shark based on RAD-seq data for 50 individuals from five sampling sites in the Indo-Pacific (IP) and one in the Atlantic Ocean (AO) to decipher the extent of the species' global connectivity and its demographic history. RESULTS: Clustering algorithms (PCA and NMF), FST and an approximate Bayesian computation framework revealed the presence of two clusters corresponding to the two oceanic basins. By modelling the two-dimensional site frequency spectrum, we tested alternative isolation/migration scenarios between these two identified populations. We found the highest support for a divergence time between the two ocean basins of ~ 193,000 years before present (B.P) and an ongoing but limited asymmetric migration ~ 176 times larger from the IP to the AO (Nm ~ 3.9) than vice versa (Nm ~ 0.02). CONCLUSIONS: The two oceanic regions are isolated by a strong barrier to dispersal more permeable from the IP to the AO through the Agulhas leakage. We finally emphasized contrasting recent demographic histories for the two regions, with the IP characterized by a recent bottleneck around 2000 years B.P. and the AO by an expansion starting 6000 years B.P. The large differentiation between the two oceanic regions and the absence of population structure within each ocean basin highlight the need for two large management units and call for future conservation programs at the oceanic rather than local scale, particularly in the Indo-Pacific where the population is declining.
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Tubarões , Animais , Teorema de Bayes , Tubarões/genética , Oceano Atlântico , Repetições de Microssatélites/genética , Oceanos e MaresRESUMO
Correctly delimiting species and populations is a prerequisite for studies of connectivity, adaptation and conservation. Genomic data are particularly useful to test species differentiation for organisms with few informative morphological characters or low discrimination of cytoplasmic markers, as in Scleractinians. Here we applied Restriction site Associated DNA sequencing (RAD-sequencing) to the study of species differentiation and genetic structure in populations of Pocillopora spp. from Oman and French Polynesia, with the objectives to test species hypotheses, and to study the genetic structure among sampling sites within species. We focused here on coral colonies morphologically similar to P. acuta (damicornis type ß). We tested the impact of different filtering strategies on the stability of the results. The main genetic differentiation was observed between samples from Oman and French Polynesia. These samples corresponded to different previously defined primary species hypotheses (PSH), i.e., PSHs 12 and 13 in Oman, and PSH 5 in French Polynesia. In Oman, we did not observe any clear differentiation between the two putative species PSH 12 and 13, nor between sampling sites. In French Polynesia, where a single species hypothesis was studied, there was no differentiation between sites. Our analyses allowed the identification of clonal lineages in Oman and French Polynesia. The impact of clonality on genetic diversity is discussed in light of individual-based simulations.
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Antozoários , Animais , Antozoários/genética , Estruturas Genéticas , Metagenômica , Análise de Sequência de DNA , Especificidade da EspécieRESUMO
Holothurians are marine invertebrates that are among the most widespread benthic megafauna communities by both biomass and abundance in shallow-water and deep-sea ecosystems, their functions supporting important ecological services worldwide. Despite their simple appearance as sea cucumbers, holothurians show a wide range of feeding practices. However, information on what and how these animals eat is scattered and potentially confusing. We provide a comprehensive review of holothurian nutrition in coastal and deep-sea ecosystems. First, we describe morphological aspects of holothurian feeding and the ultrastructure of tentacles. We discuss the two processes for food capture, concluding that mucus adhesion is likely the main method; two mucous cells, type-1 and type-2, possibly allow the adhesion and de-adhesion, respectively, of food particles. Secondly, this review aims to clarify behavioural aspects of holothurian suspension- and deposit-feeding. We discuss the daily feeding cycle, and selective feeding strategies. We conclude that there is selectivity for fine and organically rich particles, and that feeding through the cloaca is also a route for nutrient absorption. Third, we provide a wide description of the diet of holothurians, which can be split into two categories: living and non-living material. We suggest that Synallactida, Molpadida, Persiculida, Holothuriida and Elasipodida, ingest the same fractions, and emphasise the importance of bacteria in the diet of holothurians.
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Ecossistema , Pepinos-do-Mar , Animais , BiomassaRESUMO
Each year, 75-100 unprovoked shark attacks on humans are recorded, most of them resulting in no or minor injuries, while a few are fatal. Often, shark identification responsible for attacks relies on visual observations or bite wound characteristics, which limits species determination and preclude individual identification. Here, we provide two genetic approaches to reliably identify species and/or individuals involved in shark attacks on humans based on a non-invasive DNA sampling (i.e. DNA traces present on bite wounds on victims), depending on the knowledge of previous attack history at the site. The first approach uses barcoding techniques allowing species identification without any a priori, while the second relies on microsatellite genotyping, allowing species identification confirmation and individual identification, but requiring an a priori of the potential species involved in the attack. Both approaches were validated by investigating two shark attacks that occurred in Reunion Island (southwestern Indian Ocean). According to both methods, each incident was attributed to a bull shark (Carcharhinus leucas), in agreement with suggestions derived from bite wound characteristics. Both approaches appear thus suitable for the reliable identification of species involved in shark attacks on humans. Moreover, microsatellite genotyping reveals, in the studied cases, that two distinct individuals were responsible of the bites. Applying these genetic identification methods will resolve ambiguities on shark species involved in attacks and allow the collection of individual data to better understand and mitigate shark risk.
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Mordeduras e Picadas , Tubarões , Animais , DNA/genética , Genética Forense , Humanos , Tubarões/genéticaRESUMO
Anomalous heat waves are causing a major decline of hard corals around the world and threatening the persistence of coral reefs. There are, however, reefs that have been exposed to recurrent thermal stress over the years and whose corals appear to have been tolerant against heat. One of the mechanisms that could explain this phenomenon is local adaptation, but the underlying molecular mechanisms are poorly known. In this work, we applied a seascape genomics approach to study heat stress adaptation in three coral species of New Caledonia (southwestern Pacific) and to uncover the molecular actors potentially involved. We used remote sensing data to characterize the environmental trends across the reef system, and sampled corals living at the most contrasted sites. These samples underwent next generation sequencing to reveal single nucleotide polymorphisms (SNPs), frequencies of which were associated with heat stress gradients. As these SNPs might underpin an adaptive role, we characterized the functional roles of the genes located in their genomic region. In each of the studied species, we found heat stress-associated SNPs located in proximity of genes involved in pathways well known to contribute to the cellular responses against heat, such as protein folding, oxidative stress homeostasis, inflammatory and apoptotic pathways, and DNA damage-repair. In some cases, the same candidate molecular targets of heat stress adaptation recurred among species. Together, these results underline the relevance and the power of the seascape genomics approach for the discovery of adaptive traits that could allow corals to persist across wider thermal ranges.
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Antozoários , Animais , Antozoários/genética , Recifes de Corais , Genômica , Resposta ao Choque Térmico/genética , Nova CaledôniaRESUMO
Investigations of the genetic structure of populations over the entire range of a species yield valuable information about connectivity among populations. Seabirds are an intriguing taxon in this regard because they move extensively when not breeding, facilitating intermixing of populations, but breed consistently on the same isolated islands, restricting gene flow among populations. The degree of genetic structuring of populations varies extensively among seabird species but they have been understudied in their tropical ranges. Here, we address this across a broad spatial scale by using microsatellite and mitochondrial data to explore the population connectivity of 13 breeding populations representing the six subspecies of the white-tailed tropicbird (Phaethon lepturus) in the Atlantic, Indian, and Pacific Oceans. Our primary aim was to identify appropriate conservation units for this little known species. Three morphometric characters were also examined in the subspecies. We found a clear pattern of population structuring with four genetic groups. The most ancient and the most isolated group was in the northwestern Atlantic Ocean. The South Atlantic populations and South Mozambique Channel population on Europa were genetically isolated and may have had a common ancestor. Birds from the Indo-Pacific region showed unclear and weak genetic differentiation. This structuring was most well defined from nuclear and mtDNA markers but was less well resolved by morphological data. The validity of classifying white-tailed tropicbirds into six distinct subspecies is discussed in light of our new findings. From a conservation standpoint our results highlight that the three most threatened conservation units for this species are the two subspecies of the tropical North and South Atlantic Oceans and that of Europa Island in the Indian Ocean.
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We investigated the occurrence of intracolonial genetic variability (IGV) in Pocillopora corals in the southwestern Indian Ocean. Ninety-six colonies were threefold-sampled from three sites in Reunion Island. Nubbins were genotyped using 13 microsatellite loci, and their multilocus genotypes compared. Over 50% of the colonies presented at least two different genotypes among their three nubbins, and IGV was found abundant in all sites (from 36.7% to 58.1%). To define the threshold distinguishing mosaicism from chimerism, we developed a new method based on different evolution models by computing the number of different alleles for the infinite allele model (IAM) and the Bruvo's distance for the stepwise mutation model (SMM). Colonies were considered as chimeras if their nubbins differed from more than four alleles and if the pairwise Bruvo's distance was higher than 0.12. Thus 80% of the IGV colonies were mosaics and 20% chimeras (representing almost 10% of the total sampling). IGV seems widespread in scleractinians and beyond the disabilities of this phenomenon reported in several studies, it should also bring benefits. Next steps are to identify these benefits and to understand processes leading to IGV, as well as factors influencing them.
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Multiple paternity seems common within elasmobranchs. Focusing on two deep-sea shark species, the velvet belly lanternshark (Etmopterus spinax) and the slendertail lanternshark (Etmopterus molleri) we inferred the paternity in 31 E. spinax litters from Norway (three to 18 embryos per litter) and six E. molleri litters from Japan (three to six embryos), using 21 and 10 specific microsatellites, respectively. At least two E. spinax litters were sired from multiple fathers each, with highly variable paternal skew (1:1 to 9:1). Conversely, no clear signal of genetic polyandry was found in E. molleri.
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Comportamento Sexual Animal/fisiologia , Tubarões/fisiologia , Animais , Escuridão , Feminino , Japão , Masculino , Repetições de Microssatélites/genética , Noruega , PaternidadeRESUMO
BACKGROUND: In recent years, the Asian tiger mosquito Aedes albopictus has emerged as a species of major medical concern following its global expansion and involvement in many arbovirus outbreaks. On Réunion Island, Ae. albopictus was responsible for a large chikungunya outbreak in 2005-2006 and more recently an epidemic of dengue which began at the end of 2017 and is still ongoing at the time of writing. This dengue epidemic has seen a high number of human cases in south and west coastal regions, while few cases have been reported in the north and east of the island. To better understand the role of mosquito populations in such spatial patterns of dengue virus transmission in Réunion Island, we examined the genetic diversity and population structure of Ae. albopictus sampled across the island. RESULTS: Between November 2016 and March 2017, a total of 564 mosquitoes were collected from 19 locations in three main climatic regions (West, East and Center) of Réunion Island and were genotyped using 16 microsatellite loci. A high genetic diversity was observed with 2-15 alleles per locus and the average number of alleles per population varying between 4.70-5.90. Almost all FIS values were significantly positive and correlated to individual relatedness within populations using a hierarchical clustering approach based on principal components analyses (HCPC). However, the largest part of genetic variance was among individuals within populations (97%) while only 3% of genetic variance was observed among populations within regions. Therefore, no distinguishable population structure or isolation by distance was evidenced, suggesting high rates of gene flow at the island scale. CONCLUSIONS: Our results show high genetic diversity but no genetic structure of Ae. albopictus populations in Réunion Island thus reflecting frequent movements of mosquitoes between populations probably due to human activity. These data should help in the understanding of Ae. albopictus vector capacity and the design of effective mosquito control strategies.
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Aedes/genética , Variação Genética , Mosquitos Vetores/genética , Aedes/classificação , Aedes/fisiologia , Animais , Febre de Chikungunya/transmissão , Dengue/transmissão , Genótipo , Humanos , Ilhas , Repetições de Microssatélites , Mosquitos Vetores/classificação , Mosquitos Vetores/fisiologia , ReuniãoRESUMO
Knowledge of population structure, connectivity, and effective population size remains limited for many marine apex predators, including the bull shark Carcharhinus leucas. This large-bodied coastal shark is distributed worldwide in warm temperate and tropical waters, and uses estuaries and rivers as nurseries. As an apex predator, the bull shark likely plays a vital ecological role within marine food webs, but is at risk due to inshore habitat degradation and various fishing pressures. We investigated the bull shark's global population structure and demographic history by analyzing the genetic diversity of 370 individuals from 11 different locations using 25 microsatellite loci and three mitochondrial genes (CR, nd4, and cytb). Both types of markers revealed clustering between sharks from the Western Atlantic and those from the Western Pacific and the Western Indian Ocean, with no contemporary gene flow. Microsatellite data suggested low differentiation between the Western Indian Ocean and the Western Pacific, but substantial differentiation was found using mitochondrial DNA. Integrating information from both types of markers and using Bayesian computation with a random forest procedure (ABC-RF), this discordance was found to be due to a complete lack of contemporary gene flow. High genetic connectivity was found both within the Western Indian Ocean and within the Western Pacific. In conclusion, these results suggest important structuring of bull shark populations globally with important gene flow occurring along coastlines, highlighting the need for management and conservation plans on regional scales rather than oceanic basin scale.
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Scleractinia of the Maputaland reef complex (MRC) in South Africa exist at the margins of the Western Indian Ocean (WIO) coral distribution and are the only substantial hermatypic coral communities in South Africa. Pocillopora species occupy a conspicuous component of the MRC, and previous investigations identified three species of Pocillopora utilizing conventional taxonomy. Thus, our aims were four-fold: to elucidate Pocillopora species diversity using genetic techniques, primarily using species delimitation methods based on the ORF gene; to test for the presence of hybridisation within the Pocillopora community on the South-West margin of distribution in the Indian Ocean using two nuclear and two mitochondrial markers; to test the presence of cryptic species, using 13 microsatellite markers, finally, to elucidate the degree of genetic diversity within each Pocillopora species found and compare this to communities in lower latitudes. We illustrate taxonomic inconsistencies between these inventories and our phylogenetic data. The MRC harbours unique populations of Pocillopora, consisting of three species hypothetically co-occurring throughout the south WIO, namely: P. meandrina/P. eydouxi, commonly misidentified as P. verrucosa, P. verrucosa, sometimes correctly identified, but also commonly misidentified as P. damicornis sensu lato, and P. villosa, almost always misidentified as P. eydouxi. The hypothesis that hybrid swarms of Pocillopora occur in marginal environments such as the MRC was not supported, with low levels of introgressive hybridization reported instead. Analyses illustrate low genetic diversity at the species and population resolutions, suggesting a small founder population for each species. Nevertheless, these populations are demographically unique, exhibiting high levels of ITS2 haplotype endemism compared to higher latitude populations and the rest of the WIO. Pocillopora diversity on the MRC represents a unique assemblage and warrants further protection.
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Antozoários/genética , Recifes de Corais , Variação Genética , Repetições de Microssatélites , Animais , Haplótipos , Oceano Índico , África do SulRESUMO
To improve understanding of bull shark Carcharhinus leucas reproductive biology, we analysed reproductive traits from 118 bull sharks caught along Reunion Island coasts (Western Indian Ocean), including 16 gravid females. Specific microsatellite loci were used to investigate the frequency of multiple paternity. Males and females reached maturity at c. 234 cm and 257 cm total length (LT ), respectively, and litter sizes ranged from 5 to 14 embryos. Analysis of the 16 litters collected in various months of the year indicated that parturition occurs between October and December, with a size at birth c. 60-80 cm LT and that the gestation period is probably c. 12 months. Assuming a 1 year resting period and a period of sperm storage (4-5 months) between mating (in June-September) and fertilisation, the reproductive cycle of bull sharks at Reunion Island would be biennial. At least 56.25% of the litters investigated were polyandrous, sired by 2-5 males. Several males that each sired several litters conceived during the same or distinct mating seasons were detected, suggesting both a seasonal aggregation of sharks to mate and some male fidelity to mating site. Altogether, these findings provide valuable information for both shark risk management and conservation of the species in the Western Indian Ocean.
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Comportamento Sexual Animal , Tubarões/fisiologia , Animais , Feminino , Oceano Índico , Masculino , Repetições de Microssatélites , Paternidade , Reprodução , Reunião , Estações do Ano , Tubarões/genéticaRESUMO
The prickly redfish Thelenota ananas (Jaeger, 1833) is a widely distributed tropical sea cucumber. Populations of this species have been increasingly harvested throughout its distribution area in the Indo-Pacific region, which led to significant overexploitation issues. In order to investigate the genetic structure, diversity and connectivity of its populations, 42 microsatellite loci were isolated from a T. ananas microsatellite-enriched DNA library. These loci were characterized on 24 individuals collected from the Seychelles. The number of alleles per locus ranged from 3 to 22. The observed heterozygosity ranged from 0.083 to 0.952, while the expected heterozygosity ranged from 0.162 to 0.974. No linkage disequilibrium was detected among all loci and 20 loci (48%) were at Hardy-Weinberg equilibrium. These 42 loci represent useful tools for assessing genetic diversity, structure and gene flow among T. ananas populations, providing relevant knowledge for the management and conservation of those major commercial resources.
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Pepinos-do-Mar/genética , Animais , Equinodermos/genética , Fluxo Gênico/genética , Loci Gênicos/genética , Heterozigoto , Desequilíbrio de Ligação , Repetições de Microssatélites , Perciformes/genética , Polimorfismo GenéticoRESUMO
Population genetics has been increasingly applied to study large sharks over the last decade. Whilst large shark species are often difficult to study with direct methods, improved knowledge is needed for both population management and conservation, especially for species vulnerable to anthropogenic and climatic impacts. The tiger shark, Galeocerdo cuvier, is an apex predator known to play important direct and indirect roles in tropical and subtropical marine ecosystems. While the global and Indo-West Pacific population genetic structure of this species has recently been investigated, questions remain over population structure and demographic history within the western Indian (WIO) and within the western Pacific Oceans (WPO). To address the knowledge gap in tiger shark regional population structures, the genetic diversity of 286 individuals sampled in seven localities was investigated using 27 microsatellite loci and three mitochondrial genes (CR,COI, and cytb). A weak genetic differentiation was observed between the WIO and the WPO, suggesting high genetic connectivity. This result agrees with previous studies and highlights the importance of the pelagic behavior of this species to ensure gene flow. Using approximate Bayesian computation to couple information from both nuclear and mitochondrial markers, evidence of a recent bottleneck in the Holocene (2,000-3,000 years ago) was found, which is the most probable cause for the low genetic diversity observed. A contemporary effective population size as low as 111 [43,369] was estimated during the bottleneck. Together, these results indicate low genetic diversity that may reflect a vulnerable population sensitive to regional pressures. Conservation measures are thus needed to protect a species that is classified as Near Threatened.
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Holothuria (Microthele) fuscogilva (Cherbonnier, 1980), Holothuria sp. type "Pentard" and Holothuria (Microthele) nobilis (Selenka, 1867) are three tropical sea cucumber taxa that are heavily fished worldwide for the beche-de-mer trade market. In order to investigate the population genetic structure, diversity and connectivity of these taxa, 16, 19 and 25 microsatellite loci were isolated from H. fuscogilva, Holothuria sp. type "Pentard" and H. nobilis DNA libraries, respectively. These loci were tested on 94, 60 and eight individuals of the respective species, collected from the Seychelles. The number of alleles per locus ranged from 2 to 30. The observed heterozygosity ranged from 0.245 to 0.890 for H. fuscogilva and from 0.200 to 0.950 for Holothuria sp. type "Pentard", while the expected heterozygosity ranged from 0.231 to 0.952 and from 0.504 to 0.951, respectively. Several loci were at Hardy-Weinberg equilibrium and linkage disequilibrium was detected in only three pairs of loci. Cross-amplification was also tested and almost all loci (49 over 60) were polymorphic for at least two of the three studied taxa, showing high transferability among them. These loci represent useful tools for assessing genetic diversity and population structure of these three taxa in fishery areas, and therefore providing relevant knowledge for resource management.
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Pepinos-do-Mar/genética , Animais , Equinodermos/genética , Frequência do Gene , Genética Populacional/métodos , Holothuria/genética , Desequilíbrio de Ligação , Repetições de Microssatélites , Reação em Cadeia da Polimerase/métodos , Polimorfismo Genético/genética , SeichelesRESUMO
Etmopterus spinax (Linnaeus, 1758) and Etmopterus molleri (Whitley, 1939) are two bioluminescent deep-sea sharks, usually caught in large numbers as bycatch by deep-water fisheries. Yet, no study has ever involved population status of these two species using genetic tools. In order to investigate population genetic structure, diversity and connectivity of these two lanternsharks, 29 and 19 microsatellite loci were isolated from E. spinax DNA library for E. spinax and E. molleri, respectively. These loci were tested on 32 E. spinax individuals from the North Sea and seven E. molleri from the East China Sea. The number of alleles per locus ranged from 2 to 13. The observed heterozygosity ranged from 0.031 to 0.839 for E. spinax and from 0.000 to 1.000 for E. molleri, while the expected heterozygosity ranged from 0.031 to 0.903 and from 0.143 to 0.821, respectively. Almost all loci (24 and 16, respectively) were at Hardy-Weinberg equilibrium for both species and no linkage disequilibrium among loci was detected. These loci represent useful tools to better understand the population structure of these two species. Besides, they could also be suitable for other lanternsharks in general, as these latter remain largely understudied, specially in terms of understanding the basic science that will serve into their conservation.