Rimicaris exoculata is one of the most well-known and emblematic species of endemic vent fauna. Like many other species from these ecosystems, Rimicaris shrimps host important communities of chemosynthetic bacteria living in symbiosis with their host inside the cephalothorax and gut. For many of these symbiotic partners, the mode of transmission remains to be elucidated and the starting point of the symbiotic relationship is not yet defined, but could begin with the egg. In this study, we explored the proliferation of microbial communities on R. exoculata broods through embryonic development using a combination of NGS sequencing and microscopy approaches. Variations in abundance and diversity of egg microbial communities were analyzed in broods at different developmental stages and collected from mothers at two distinct vent fields on the Mid-Atlantic Ridge (TAG and Snake Pit). We also assessed the specificity of the egg microbiome by comparing communities developing on egg surfaces with those developing on the cuticle of pleopods, which are thought to be exposed to similar environmental conditions because the brood is held under the female’s abdomen. In terms of abundance, bacterial colonization clearly increases with both egg developmental stage and the position of the egg within the brood: those closest to the exterior having a higher bacterial coverage. Bacterial biomass increase also accompanies an increase of mineral precipitations and thus clearly relates to the degree of exposure to vent fluids. In terms of diversity, most bacterial lineages were found in all samples and were also those found in the cephalothorax of adults. However, significant variation occurs in the relative abundance of these lineages, most of this variation being explained by body surface (egg vs. pleopod), vent field, and developmental stage. The occurrence of symbiont-related lineages of Epsilonbacteraeota, Gammaproteobacteria, Zetaproteobacteria , and Mollicutes provide a basis for discussion on both the acquisition of symbionts and the potential roles of these bacterial communities during egg development.

Among the endemic and specialized fauna from hydrothermal vents, Rimicaris shrimps constitute one of the most important and emblematic components of these ecosystems. On the Mid-Atlantic Ridge, 2 species belonging to this genus co-occur: R. exoculata and R. chacei that differ in their morphology, trophic regime and abundance. R. exoculata forms large and dense aggregations on active vent chimney walls in close proximity to vent fluid emissions, whereas R. chacei is much less conspicuous, living mostly in scattered groups or solitary further away from the fluids. However, the recent revision of Rimicaris juvenile stages from the Mid-Atlantic Ridge shows that R. chacei abundance would be higher than expected at these early life stages. Here, we describe and compare the population structure of R. exoculata and R. chacei at the Snake Pit and Trans-Atlantic Geotraverse (TAG) vent fields. We show distinct population demographics between the 2 co-occurring shrimp species with a large post-settlement collapse in R. chacei populations suggesting high juvenile mortality for this species. We describe important spatial segregation patterns between the 2 species and their different life stages. Additionally, our results highlight distinct niches for the earliest juvenile stages of both R. exoculata and R. chacei, compared with all other life stages. Finally, we discuss the potential factors, including predation and competitive interactions, that could explain the differences we observed in the population structure of these 2 species.

The diversity of deep-water corals in the Caribbean Sea was studied using records from oceanographic expeditions performed by the R/V Pillsbury. Sampled stations were sorted according to broad depth ranges and ecoregions and were analyzed in terms of species accumulation curves, variance in the species composition and contributions to alpha, beta and gamma diversity. According to the analysis of species accumulation curves using the Chao2 estimator, more diversity occurs on the continental slope (200–2000 m depth) than on the upper continental shelf (60–200 m depth). In addition to the effect of depth sampling, differences in species composition related to depth ranges were detected. However, the differences between ecoregions are dependent on depth ranges, there were fewer differences among ecoregions on the continental slope than on the upper continental shelf. Indicator species for distinctness of ecoregions were, in general, Alcyonaria and Antipatharia for the upper continental shelf, but also the scleractinians Madracis myriabilis and Cladocora debilis. In the continental slope, the alcyonarian Placogorgia and the scleractinians Stephanocyathus and Fungiacyathus were important for the distinction of ecoregions. Beta diversity was the most important component of gamma diversity in the Caribbean Basin. The contribution of ecoregions to alpha, beta and gamma diversity differed with depth range. On the upper continental shelf, the Southern Caribbean ecoregion contributed substantially to all components of diversity. In contrast, the northern ecoregions contributed substantially to the diversity of the Continental Slope. Strategies for the conservation of deep-water coral diversity in the Caribbean Basin must consider the variation between ecoregions and depth ranges.

Alvinocaridid shrimps are endemic species inhabiting hydrothermal vents and/or cold seeps. Although indirect evidences (genetic and lipid markers) suggest that their larval stages disperse widely and support large scale connectivity, larval life and mechanisms underlying dispersal are unknown in alvinocaridids. Here we provide for the first time detailed descriptions of the first larval stage (zoea I) of four alvinocaridid species: Rimicaris exoculata and Mirocaris fortunata from the Mid-Atlantic Ridge, Alvinocaris muricola from the Congo Basin and Nautilocaris saintlaurentae from the Western Pacific. The larvae were obtained from onboard hatching of brooding females (either at atmospheric pressure or at habitat pressure in hyperbaric chambers) and from the water column near adult habitats, sampled with plankton pumps or sediment traps. Major characteristics of the alvinocaridid larvae include undeveloped mandible and almost complete absence of setation in the inner margin of the mouth parts and maxillipeds. Although the larvae are very similar between the four species studied, some morphological features could be used for species identification. In addition, undeveloped mouthparts and the large amount of lipid reserves strongly support the occurrence of primary lecithotrophy in the early stage of alvinocaridids. Although lecithotrophy in decapod crustaceans is usually associated with abbreviated larval development, as a mechanism of larval retention, morphological and physiological evidences suggest the occurrence of an extended and lecithotrophic larval stage in the Alvinocarididae. These traits permit the colonization of widely dispersed and fragmented environments of hydrothermal vents and cold seeps. Distribution of larval traits along the phylogenetic reconstruction of the Alvinocarididae and related families suggest that lecithotrophy/planktotrophy and extended/abbreviated development have evolved independently along related families in all potential combinations. However, the Alvinocarididae is the only taxa with a combination of lecithotrophy and extended larval development.

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A reassessment of the adult and larval morphology as well as comparison with published molecular information confirms the monophyly of the genus Calyptraeotheres Campos, 1990, and its relationship with Dissodactylus Smith, 1870, Clypeasterophilus Campos & Griffith, 1990 and Tumidotheres Campos, 1990. Calyptraeotheres pepeluisi new species, is described from Michoacán, Mexico on the basis of a female specimen. The new species is distinguished from the other nominal species of the genus by having a subarcuate carapace with longer setae on its front and anterolateral margin, the eyes are dorsally visible, and a third maxilliped with a 2-segmented palp and a conical propodus.

The crustacean decapod fauna of Cubagua Island in the Caribbean Sea, Venezuela, an island much affected by coastal upweling, was surveyed. A total of 178 species from 41 families were recorded, of which 56 species were new records for the island; eigth genera and six species were new records for Venezuela. Most species had previously been recorded from the the Caribbean province, 19.7% were endemic for the province, 64.1% had affinities to the Brazilian province, 57.3% to the Texan and Carolinian provinces and 45.5% showed continuous distributions across the provinces but showing less endemism and more affinities with Brazilian province than the general trends of distributions of decapods in the Caribbean. It appears that upwelling processes around the island hinders the development of the typical Caribbean marine ecosystems. The proximity with the northern limit of the Brazilian province also affects the biodiversity of the island.