Search

Background During the 2019 First Descent: Seychelles Expedition, shallow and deep reef ecosystems of the Seychelles Outer Islands were studied by deploying a variety of underwater technologies to survey their benthic flora and fauna. Submersibles, remotely operated vehicles (ROVs) and SCUBA diving teams used stereo-video camera systems to record benthic communities during transect surveys conducted at 10 m, 30 m, 60 m, 120 m, 250 m and 350 m depths. In total, ~ 45 h of video footage was collected during benthic transect surveys, which was subsequently processed using annotation software in order to assess reef biodiversity and community composition. Here, we present a photographic guide for the visual identification of the marine macrophytes, corals, sponges and other common invertebrates that inhabit Seychelles’ reefs. It is hoped that the resulting guide will aid marine biologists, conservationists, managers, divers and naturalists with the coarse identification of organisms as seen in underwater footage or live in the field. New information A total of 184 morphotypes (= morphologically similar individuals) were identified belonging to Octocorallia (47), Porifera (35), Scleractinia (32), Asteroidea (19), Echinoidea (10), Actiniaria (9), Chlorophyta (8), Antipatharia (6), Hydrozoa (6), Holothuroidea (5), Mollusca (2), Rhodophyta (2), Tracheophyta (2), Annelida (1), Crinoidea (1), Ctenophora (1), Ochrophyta (1) and Zoantharia (1). Out of these, we identified one to phylum level, eight to class, 14 to order, 27 to family, 110 to genus and 24 to species. This represents the first attempt to catalogue the benthic diversity from shallow reefs and up to 350 m depth in Seychelles.

Deep-water sedimentary habitats off Nova Scotia have only rarely been explored. The topographically and oceanographically complex shelf of Nova Scotia harbours two interesting topographic features, Emerald Basin, a sedimentary habitat reaching greater depths (max of 270 m) than the surrounding shelf and the Gully, the largest canyon in NW Atlantic. Emerald Basin is exposed to upwellings of slope water and harbours predominantly deep-sea hexactinellid sponges. Such distributional pattern resembles “deep-water emergence”. In this study an abundant benthic group, the polychaetes, were selected to test for such deep-water faunal link. Qualitative boxcores were collected from Emerald Basin (180 m depth, N = 5) and the adjacent Gully Canyon (1600 m, N = 3). At species level, there was no overlap in distribution between Emerald Basin (N = 73, S=29) and Gully Canyon (N = 351, S = 60) fauna based on morphological assessment of all specimens and molecular analysis (COI and 16S markers) of selected morphotypes. In an alternative approach, Multivariate analysis (nMDS, Cluster Analysis) of incidence data for polychaete genera (N = 179) from 24 Atlantic sites (5–1600 m) was carried out. These results showed a greater similarity of Emerald Basin polychaetes to bathyal sites (400–1000 m), particularly the 680 m site off Nova Scotia rather than shelf sites (5–80 m), including those on the Nova Scotia shelf. Thus, at 1600 m, the Gully Canyon samples were likely “too deep” for our comparative purposes and depths of ≺1000 m should be targeted in the future. Our data also provide the first published assessment of polychaete diversity from the Gully Canyon, suggesting the presence of a diverse assemblage (S = 60). Unusually for a deep-sea site, the Gully Canyon polychaetes are mostly known taxa with wider distribution across bathyal NW Atlantic. Additionally, our molecular data provide an interesting insights into the distribution of several polychaete species commonly found in deep-sea (e.g Aurospio dibranchiata Maciolek, 1981; Ophelina abranchiata Støp-Bowitz, 1948) suggesting wide geographical distribution for some but revealing species complexes for others.

The deep sea is the largest biome on earth, and microbes dominate in biomass and abundance. Anthropogenic litter is now almost ubiquitous in this biome, and its deposition creates new habitats and environments, including for microbial assemblages. With the ever increasing accumulation of this debris, it is timely to identify and describe the bacterial and archaeal communities that are able to form biofilms on macrodebris in the deep sea. Using 16S rRNA gene high throughput sequencing, we show for the first time the composition of bacteria and archaea on macrodebris collected from the deep sea. Our data suggest differences in the microbial assemblage composition across litter of different materials including metal, rubber, glass, fabric and plastic. These results imply that anthropogenic macrodebris provide diverse habitats for bacterial and archaeal biofilms and each may harbour distinct microbial communities.

This preprint has been peer-reviewed and recommended by Peer Community in Evolutionary Biology (PCI Evol Biol, doi: 10.24072/pci.evolbiol.100056). Diverging semi-isolated lineages either meet in narrow clinal hybrid zones, or have a mosaic distribution associated with environmental variation. Intrinsic reproductive isolation is often emphasized in the former and local adaptation in the latter, although both can contribute to isolation. Rarely these two patterns of spatial distribution are reported in the same study system. Here we report that the long-snouted seahorse Hippocampus guttulatus is subdivided into discrete panmictic entities by both types of hybrid zones. Along the European Atlantic coasts, a northern and a southern lineage meet in the southwest of France where they coexist in sympatry with little hybridization. In the Mediterranean Sea, two lineages have a mosaic distribution, associated with lagoon-like and marine habitats. A fifth lineage was identified in the Black Sea. Genetic homogeneity over large spatial scales contrasts with isolation maintained in sympatry or close parapatry at a fine scale. A high variation in locus-specific introgression rates provides additional evidence that partial reproductive isolation must be maintaining the divergence. Surprisingly, fixed differences between lagoon and marine populations in the Mediterranean Sea belong to the most differentiated SNPs between the two Atlantic lineages, against the genome-wide pattern of structure. These parallel outlier SNPs cluster on a single chromosome-wide island of differentiation. Since Atlantic lineages do not match the lagoon-sea habitat variation, genetic parallelism at the genomic island suggests a shared genetic barrier contributes to reproductive isolation in contrasting contexts -i.e. spatial vs. ecological. We discuss how a genomic hotspot of parallel differentiation could have evolved and become associated either with space or with a patchy environment in a single study system.

The effective design of species conservation programs is reliant on information such as extant geographic distribution, taxon-specific life-history characteristics, and the relative influence of historic processes and contemporary environmental parameters in shaping population genetic diversity. Seahorses are weak swimmers and have a brooded young, limiting their dispersal potential. They live in sheltered locations, which are physically isolated from each other. Therefore panmixia across their geographic range is unlikely. Hippocampus guttulatus, a seahorse inhabiting European waters, has a geographic range spanning a number of contemporary oceanographic features that are proposed barriers to gene flow. Thus this fish is well-placed to test the contributions of environment and life-history factors in shaping population structuring. This study found that mitochondrial DNA and nuclear DNA (microsatellite) genotype data are concordant in suggesting that, like many other small fishes in European waters, H. guttulatus extant populations expanded from at least one southern European refugial population. Subsequent population differentiation of four geographic lineages reflects contemporary oceanographic barriers to gene flow. Demographic analyses suggest a northward, and long-term isolation between Black Sea and Mediterranean Sea populations. Moreover H. guttulatus contemporary population distribution and population structure are predominately explained by historic and oceanographic influences. These findings suggest that conservation of genetic diversity in H. guttulatus may be aided by a network of marine protected areas (MPAs), implemented to conserve coastal habitats, but the species’ unusual life history and gamete retaining behaviours should be considered as part of management decisions including MPA design and fisheries management plans.

Accurate taxonomy, population demography, and habitat descriptors inform species threat assessments and the design of effective conservation measures. Here we combine published studies with new genetic, morphological and habitat data that were collected from seahorse populations located along the European and North African coastlines to help inform management decisions for European seahorses. This study confirms the presence of only two native seahorse species (Hippocampus guttulatus and H. hippocampus) across Europe, with sporadic occurrence of non-native seahorse species in European waters. For the two native species, our findings demonstrate that highly variable morphological characteristics, such as size and presence or number of cirri, are unreliable for distinguishing species. Both species exhibit sex dimorphism with females being significantly larger. Across its range, H. guttulatus were larger and found at higher densities in cooler waters, and individuals in the Black Sea were significantly smaller than in other populations. H. hippocampus were significantly larger in Senegal. Hippocampus guttulatus tends to have higher density populations than H. hippocampus when they occur sympatrically. Although these species are often associated with seagrass beds, data show both species inhabit a wide variety of shallow habitats and use a mixture of holdfasts. We suggest an international mosaic of protected areas focused on multiple habitat types as the first step to successful assessment, monitoring and conservation management of these Data Deficient species. Natural Environment Research Council Industrial Case studentship [NER/S/C/2005/13461]; Chocolaterie Guylian; European Commission (ASSEMBLE project) [227799] info:eu-repo/semantics/publishedVersion

Hymenopteran species with single-locus complimentary sex-determination (sl-CSD) face an additional cost of inbreeding because of a loss of diversity at the sex-determining locus. Laboratory studies of a range of Hymenoptera have found that a small percentage of diploid males produce viable diploid sperm, and that if these males mate, then the resultant females produce triploid offspring that are sterile. Here, we use microsatellite markers to determine the frequency of triploid individuals of Bombus muscorum and B. jonellus in a model island system. Triploids were found in populations of both species. Observed triploid frequencies of up to 8% were detected, and estimated total frequencies peaked at 20% with respect to normal diploid workers. For both species, triploid frequency was negatively correlated with surrogates of population size, providing direct evidence for inbreeding in small populations. Populations limited to

Partial fin-clipping is a non-lethal sampling technique commonly used to sample tissue for molecular genetic studies of fish. The effect of this technique was tested on seahorses (Hippocampus spp.) as they have several peculiar biological characteristics when compared with other fish and are on the IUCN Red List of Threatened Species. Partial fin-clipping of the seahorse dorsal fin was evaluated on Hippocampus kuda. The fish were assessed for short-term effects (fin re-growth time) as well as the longer term effects (growth and mortality) of partial fin clipping over a four month period. Total fin re-growth occurred between 2 and 4 weeks with no significant difference observed in the fin re-growth time between sexes. There was no significant difference between the mortality rate/growth rate of clipped versus unclipped seahorses. Results indicate partial fin-clipping has no significant effect on seahorses, and should be considered as a useful method for tissue sampling.

Seahorses (Hippocampus spp.) are non-sex-role-reversed members of the Syngnathidae family that provide extensive brood care. Previous studies of seahorses have revealed monogamy within a single brood, but their longer term mating system had not been comprehensively evaluated. The parental contribution to 29 wild-born broods of Hippocampus guttulatus, sampled from six Portuguese populations with differing seahorse densities and sex ratios, was assessed using microsatellite DNA markers. To assess the longer term genetic mating system of this species parentage was determined in eleven broods sampled from a captive population over two breeding seasons. Genetic data suggest that this socially polygamous seahorse is serially monogamous across breeding seasons, i.e. monogamous within a season but may switch mates between seasons, and that differing population densities and sex ratios do not affect the mating system.

A seahorse specimen from Banco Açores (Azores Archipelago) was identified using morphological and molecular genetic data as Hippocampus erectus. This specimen represents the first record of H. erectus in the eastern Atlantic Ocean, well outside its reported range, and may provide evidence of long-distance translocation in what are assumed to be relatively sedentary fish.

Mate competition and mate choice are not mutually exclusive behaviors. Both behaviors may drive sexual selection in one or both sexes of a population. One of several factors affecting which behavior is exhibited by which sex is the operational sex ratio (OSR) in the study population. The present study combines behavioral observations in the field with controlled experiments in aquaria to investigate social interactions and mate choice in both male and female long-snouted seahorses Hippocampus guttulatus in the context of the population OSR. Compared with the more readily studied pipefishes, data on OSR and mate choice in seahorses are scarce in the published literature. Our field data provide novel evidence of social promiscuity, size-assortative mating, and an OSR that varies from being unbiased early and midseason to male biased at the end of the breeding season. Our mate choice experiments revealed intersexual differences in mate preference with males significantly preferring larger females to familiar ones. Taken together, our field and experimental results suggest that mate choice rather than intrasexual competition could drive sexual selection in seahorses. Key words: assortative mating, reproductive behavior, sexual selection, Syngnathidae. [Behav Ecol]

Bumblebees are ecologically and economically important, and some species have suffered dramatic population declines. The absence of morphological diagnostic characters for the identification of some species creates difficulties for basic ecological studies, and for conservation management. The widespread and commercially exploited bumblebee subgenus Bombus sensu stricto contains a cryptic species complex, known as the lucorum complex, which in Europe comprises B. lucorum, B. cryptarum and B. magnus. Little is known about these species and much of what has been reported is likely to have suffered from incorrect identification. Although the lucorum complex as a whole is common in Great Britain, we aimed to determine whether the populations of the individual species are vulnerable and require conservation action. Using genetic methods to distinguish them, we determined the geographic distribution and abundance of the lucorum complex species in Great Britain, and assessed the extent of niche differentiation between these species. We detected major differences in the geographic range, forage use and sensitivity to summer temperatures of the three species. Bombus lucorum was found to have the broadest distribution and diet, being present throughout mainland Great Britain, whereas B. cryptarum and B. magnus were absent from large areas of central and southern England. Bombus cryptarum and B. magnus were more likely to be found at sites with lower summer temperatures. Bombus magnus, the least abundant species, was found to exhibit an unusually tight biotope association with heathland habitat. This has conservation implications for B. magnus given the current threats to this habitat type.

Genetic studies provide valuable data to inform conservation strategies for species with small or declining populations. In these circumstances, obtaining DNA samples without harming the study organisms is highly desirable. Excrements are increasingly being used as a source of DNA in such studies, but such approaches have rarely been applied to arthropods. Bumblebees are ecologically and economically important as pollinators; however, some species have recently suffered severe declines and range contractions across much of Western Europe and North America. We investigated whether bumblebee faeces could be used for the extraction of DNA suitable for genotyping using microsatellite markers. We found that DNA could be extracted using a Chelex method from faecal samples collected either in microcapillary tubes or on filter paper, directly from captured individuals. Our results show that genotypes scored from faecal samples are identical to those from tissue samples. This study describes a reliable, consistent and efficient noninvasive method of obtaining DNA from bumblebees for use in population genetic studies. This approach should prove particularly useful in breeding and conservation programs for bumblebees and may be broadly applicable across insect taxa.

This first genetic study of Hippocampus hippocampus covers the species' entire geographic range and employs two mtDNA markers (control region and cytochrome b) to establish patterns of population structuring. A total of 255 specimens from 21 locations were used to obtain 89 concatenated haplotypes. The common haplotype was present in all but one population, however, most haplotypes were unique. The haplotype network had a star-like construction, suggesting expansion from a bottleneck event. F(ST) and AMOVA revealed population subdivision into three geographic regions (English Channel + Bay of Biscay, Mediterranean Sea + Atlantic Ocean Iberian coast + Macaronesian Islands, and West Africa) with barriers to gene flow indentified at Cape Finisterre and the Cape Verde frontal zone. Neutrality tests and nested clade analysis suggest a complex demographic history, with both historic events and contemporary processes shaping patterns of genetic differentiation. The genetic population subdivision detected in this study indicates that H. hippocampus should be managed as three separate units. This is especially pertinent as H. hippocampus populations within the West African region are the only ones known to be specifically targeted for exploitation.

Zooplankton form a trophic link between primary producers and higher trophic levels, and exert significant influence on the vertical transport of carbon through the water column (‘biological carbon pump’). Using a MultiNet we sampled and studied mesozooplankton communities (i.e.>0.2 mm) from six locations around Bermuda targeting four depth zones: ∼0–200 m, ∼200–400 m, ∼400–600m (deep-scattering layer), and ∼600–800 m. Copepoda, our focal taxonomic group, consistently dominated samples (∼80% relative abundance). We report declines in zooplankton and copepod abundance with depth, concurrent with decreases in food availability. Taxonomic richness was lowest at depth and below the deep-scattering layer. In contrast, copepod diversity peaked at these depths, suggesting lower competitive displacement in these more food-limited waters. Finally, omnivory and carnivory, were the dominant trophic traits, each one affecting the biological carbon pump in a different way. This highlights the importance of incorporating data on zooplankton food web structure in future modelling of global ocean carbon cycling.

Non-native lionfish have been recorded throughout the western Atlantic on both shallow and mesophotic reefs, where they have been linked to declines in reef health. In this study we report the first lionfish observations from the deep sea (>200 m) in Bermuda and Roatan, Honduras, with lionfish observed to a maximum depth of 304 m off the Bermuda platform, and 250 m off West End, Roatan. Placed in the context of other deeper lionfish observations and records, our results imply that lionfish may be present in the 200–300 m depth range of the upper-bathyal zone across many locations in the western Atlantic, but currently are under-sampled compared to shallow habitats. We highlight the need for considering deep-sea lionfish populations in future invasive lionfish management.