Specimens of galatheoid and chirostyloid squat lobsters were collected during a scientific cruise to the Saya de Malha Bank in the southwestern Indian Ocean. Nineteen species were identified, including three new species belonging to the genera Coralliogalathea Baba & Javed, 1974, Galathea Fabricius, 1793 and Trapezionida Macpherson & Baba, 2022. The present paper provides systematic accounts of the three new species, along with new locality records of other species. Molecular data are provided to support the identification and differentiation of each new species.

Galathea tukitukimea sp. nov. is described from the seamounts near Rapa Nui (Easter Island) and represents the first record of the genus for this region of the Pacific Ocean and for Chilean territory. The new species belongs to the group of species having the carapace with median protogastric and cardiac spines. G. tukitukimea has always been observed associated with the sea urchin Stereocidaris nascaensis. This potential mimicry-based association is uncommon in squat lobsters, which warrants further study.

Collections of a recent expedition to Guinea-Bissau, West Africa conducted by the Spanish Institute of Oceanography contain five specimens of two unusual species of the squat lobster genus Uroptychus Henderson, 1888, taken at 909 m depth. One of these represents an unidentified species herein described as U. pauroptilus sp. nov. and the other four are referable to U. nitidus (A. Milne Edwards, 1880), so far known only from the western Atlantic. The morphological relationships between the new species and its close relatives U. maroccanus Türkay, 1976 and U. tuerkayi Baba & Macpherson, 2017, both from the eastern Atlantic, are discussed. The identity of U. nitidus was confirmed by morphological and molecular analyses of a large series of specimens from the western and eastern Atlantic and by comparison with material of U. concolor (A. Milne-Edwards & Bouvier, 1894) from the eastern Atlantic. Phylogenetic relationships of these species as well as additional comparable species are discussed.

Environmental gradients in the sea may coincide with phenotypic or genetic gradients resulting from an evolutionary balance between selection and dispersal. The population differentiation of the swimming crab, Liocarcinus depurator, an important by-catch species in the Mediterranean Sea and North-East Atlantic, was assessed using both genetic and morphometric approaches. A total of 472 specimens were collected along its distribution area, and 17 morphometric landmarks, one mitochondrial gene (COI) and 11 polymorphic microsatellite markers were scored in 350, 287 and 280 individuals, respectively. Morphometric data lacked significant differences, but genetic analyses showed significant genetic differentiation between Atlantic and Mediterranean populations, with a steeper gradient in COI compared to microsatellite markers. Interestingly, nuclear differentiation was due to an outlier locus with a gradient in the Atlantic-Mediterranean transition area overlapping with the mtDNA gradient. Such overlapping clines are likely to be maintained by natural selection. Our results suggest a scenario of past isolation with local adaptation and secondary contact between the two basins. Local adaptation during the process of vicariance may reinforce genetic differentiation at loci maintained by environmental selection even after secondary contact.

Early-life stages play a key role in the dynamics of bipartite life cycle marine fish populations. Difficult to monitor, observations of these stages are often scattered in space and time. While Mediterranean coastlines have often been surveyed, no effort has been made to assemble historical observations. Here we build an exhaustive compilation of dispersal traits for coastal fish species, considering in situ observations and growth models (Di Stefano et al., 2023; https://doi.org/10.17882/91148). Our database contains over 110 000 entries collected from 1993 to 2021 in various subregions. All observations are harmonized to provide information on dates and geolocations of both spawning and settlement, along with pelagic larval durations. When applicable, missing data and associated confidence intervals are reconstructed from dynamic energy budget theory. Statistical analyses allow traits’ variability to be revisited and sampling biases to be revealed across taxa, space and time, hence providing recommendations for future studies and sampling. Comparison of observed and modelled entries provides suggestions to improve the feed of observations into models. Overall, this extensive database is a crucial step to investigate how marine fish populations respond to global changes across environmental gradients.

Seagrass meadows are biodiversity hotspots for invertebrate species' including decapods. Understanding the drivers of species abundance, richness and diversity of decapod assemblages is crucial for the conservation of such hotspots, but how drivers act across multiple spatial scales remains unexplored. Here we describe the decapod assemblages of Posidonia oceanica seagrass meadows and assess the influence of attributes from three increasing spatial scales (habitat, landscape, and geographical levels) on the assemblages’ structure and composition, as well as the variability partitioning among each one of these levels. Overall, geographical level attributes (i.e., inlet aperture, confinement) affected the most the decapod assemblages, while we only found a modest contribution from habitat (e.g., detritus biomass, sediment organic matter) and landscape attributes (e.g. fragmentation). We suggest that decapod assemblages are driven by the interaction of multiple processes occurring at different scales and other highly stochastic phenomena such as larval dispersion and recruitment.

Environmental gradients in the sea may coincide with phenotypic or genetic gradients resulting from an evolutionary balance between selection and dispersal (i.e. marine clines). The population differentiation of the harbour crab, Liocarcinus depurator, an important by-catch species in the Mediterranean Sea and North-East Atlantic, was assessed here using both genetic and morphometric approaches. A total of 472 specimens were collected along its distribution area, and 17 morphometric landmarks, one mitochondrial gene (COI) and 11 polymorphic microsatellite markers were scored in 350, 287 and 280 individuals, respectively. Morphometric data lacked significant differences, but genetic analyses showed a reduction in gene flow between Atlantic and Mediterranean populations, with a steeper gradient in COI compared to microsatellite markers. Interestingly, nuclear differentiation was due to an outlier locus overlapping with the mtDNA genetic gradient. Such overlapping clines are likely to be maintained by natural selection along the Atlantic-Mediterranean transition area. Our results suggest a scenario of past isolation with local adaptation and secondary contact between the two basins. The process of vicariance may reinforce genetic differentiation at loci maintained by environmental selection even after secondary contact.

Specimens of squat lobsters belonging to the family MunididaeAhyong et al., 2010, representing the genera Garymunida Macpherson & Baba, 2022, Trapezionida Macpherson & Baba, 2022 and Typhlonida Macpherson & Baba, 2022, were collected during several cruises around New Caledonia and Papua New Guinea, Southwest Pacific. The integrative study of these specimens revealed the presence of one new species in Garymunida, five in Trapezionida and one in Typhlonida. We describe and illustrate these new species, providing some new data on the taxonomy of several rare or scarcely studied species of Trapezionida. Molecular data from different markers (mitochondrial and nuclear) was also included, based on data availability, to support the taxonomic status of different species. Finally, a key to species for each genus is also provided.

After 50 years, the dumping of red mud at the head of Cassidaigne Canyon (Southern France) was stopped in 2015. The area was surveyed in 2021 with an ROV at depths of 440–630 m. Biological findings reported here (images, sampling) have been obtained during a single ROV transect in the heavily impacted zone. In spite of the industrial waste deposit, a diverse faunal assemblage has persisted at the canyon head. Bioconstruction comprising large deep-sea oyster shells, scleractinian corals and hexactinellid sponge skeletons provides elevate and complex substrates for other organisms. Among the more significant findings, three live specimens of Neopycnodonte zibrowii Gofas, C. Salas & Taviani, 2009, previously only known as dead shells in that canyon, were documented and the rarely observed stenopodid shrimp Odontozona edwardsi (Bouvier, 1908) has been sampled (first record in the Mediterranean) and DNA barcoded.

A new assessment of the global biodiversity of decapod Crustacea (to 31 December 2022) records 17,229 species in 2,550 genera and 203 families. These figures are derived from a well-curated dataset maintained on the online platform DecaNet, a subsidiary of the World Register of Marine Species (WoRMS). Distinct phases are recognised in the discovery process (as measured by species descriptions) corresponding to major historical and geopolitical time periods, with the current rate of species descriptions being more than three times higher than in the Victorian age of global exploration. Future trends are briefly explored, and it is recognised that a large number of species remain to be discovered and described.

Specimens of munidid squat lobsters belonging to the genera Heteronida Baba & de Saint Laurent, 1996 and Torbenella Baba, 2008 were collected in scientific expeditions made by several French cruises along the southwestern Pacific. These specimens were identified as two species (one new) of Heteronida and six species (four new) of Torbenella. The present paper provides systematic accounts of the five new species, along with new locality records of known species shown by this material and color information where available. Molecular data is provided to support the systematic status of each new species. A key to species for each of the genera is also presented.

Specimens of munidid squat lobsters belonging to the genera Heteronida Baba & de Saint Laurent, 1996 and Torbenella Baba, 2008 were collected in scientific expeditions made by several French cruises along the southwestern Pacific. These specimens were identified as two species (one new) of Heteronida and six species (four new) of Torbenella. The present paper provides systematic accounts of the five new species, along with new locality records of known species shown by this material and color information where available. Molecular data is provided to support the systematic status of each new species. A key to species for each of the genera is also presented.

Mortality at early life stages of fishes is common in nature and can be shaped by stochastic and selective processes. Selective mortality has rarely been assessed in natural conditions but can now be studied by combining genomic data with information on different life stages that realates to fitness. Here we investigate selective mortality between settlers and six-month survivors of the sharpsnout seabream by genotype-phenotype/environmental association studies in three localities along a geographic gradient. We gathered information on 105 individuals at 85,031 SNPs, obtained from individual based 2b-RAD libraries, as well as 9 phenotypic and environmental variables derived from individual otolith readings. We found common signals across localities for potential selection, such as lower survival rates for individuals hatching earlier, growing faster and experiencing higher temperatures during their planktonic phase. We identified 122 loci with parallel significant association to phenotypic and environmental variables. Importantly, one of these loci mapped to the exonic region of the il20rb , a gene involved in immune response, in the phylogenetically closest reference genome, showing parallel frequency changes in non-synonymous mutations in the three studied populations. Further temporal assessments are needed to understand how polymorphisms that are key to selective mortality are maintained.

During two deep-sea expeditions off the island of Guadeloupe, French West Indies, several specimens belonging to Munida and Munidopsis (Galatheoidea) were collected. Further study, integrating morphological and molecular data, indicated that some of the specimens belonged to three undescribed species, one to Munida and two to Munidopsis. Munida anteaen. sp. is morphologically closely related to the Atlantic species M. microphthalma A. . Both species can be easily distinguished morphologically and represent independent evolutionary lineages. The closest relative to Munidopsis balconin. sp. is M. glabra from the Gulf of Mexico. They can be distinguished by the armature of the carapace and pereiopods, among other differences. Munidopsis pholidotan. sp. is sister to M. squamosa (A. ) and both are considered cryptic species, distinguished only by molecular characters and subtle morphological differences like the number of epipodites. Our phylogenetic results show some monophyletic groups within Munidopsis and Munida, and the existence of morphological convergences.

The exceptional hidden diversity included in the squat lobster genus Phylladiorhynchus and its wide bathymetric and geographic range make it an interesting group to thoroughly study its evolutionary history. Here we have analyzed the entire currently known species diversity of Phylladiorhynchus using an integrative approach that includes morphological and molecular characters. The aim was to establish whether depth range (bathymetry) has played a role in their morphological and molecular evolution and in their diversification pathways. Phylogenetic analyses recovered the genus as monophyletic and as the sister group of Coralliogalathea, conforming with current systematic hypotheses, although their placement in a monophyletic Galatheidae is doubted. All the analyzed species represent well-supported lineages, structured in ten clades, correlated in most part with the morphological phylogeny. The reconstruction of ancestral habitat showed that the most recent common ancestor of Phylladiorhynchus most likely lived in shallow water environments. The divergence time estimation analyses dated the origin of the genus back to the Upper Jurassic, preceding the origin of all the other galatheoid lineages. Morphological analyses suggested that species from deeper waters exhibit greater morphological divergences and lower genetic divergences in comparison to species from shallower waters. In Phylladiorhynchus, the colonization of deeper waters has taken place independently multiple times since the Lower-Cretaceous. Our reconstruction of ancestral habitat suggests that shallow water ancestors might show an acceleration in the molecular rate of evolution and a slowdown in the rates of morphological evolution in comparison to deep sea lineages. However, although lineages from shallow and deep sea habitats show slight differences in diversification trends, bathymetry does not significantly affect the diversification rate in Phylladiorhynchus according to our diversification analyses.

The history of colonization and dispersal of fauna among deep-sea chemosynthetic ecosystems remains enigmatic and poorly understood. The distribution of squat lobsters of the genus Munidopsis Whiteaves, 1874 can be influenced by the rich organic matter and associated organism communities of chemosynthetic ecosystems. The present work analyzed the molecular relationships and morphology of individuals from different populations of Munidopsis exuta Macpherson & Segonzac, 2005 and M. geyeri Pequegnat & Pequegnat, 1970 in such ecosystems along the Atlantic Equatorial Belt, including the Chapopote Knoll, in the southern Gulf of Mexico. Munidopsis geyeri is re-described based on the present findings and reference to the literature. This analysis documented the genetic distances, as well as range of variation in the diagnostic characters that support the separation of M. exuta and M. geyeri. Our results confirm that the two species coexist in seep ecosystems and have an amphi-Atlantic distribution.

Unravelling the evolutionary history of taxa requires solid delimitation of the traits characterising these. This can be challenging especially in groups with a highly complex taxonomy. The squat lobster family Munididae contains more than 450 species distributed among 21 genera, Munida being the most speciose (similar to 300 species). Previous phylogenetic studies, based on a small part of the diversity of the group, have suggested polyphyletic origins for Munida and the paraphyly of Munididae. Here, we use an integrative approach based on multi-locus phylogenies (two mitochondrial and three nuclear markers) paired with 120 morphological characters, to resolve taxonomic and evolutionary relationships within Munididae. Our study covers similar to 60% of the family's known diversity (over 800 specimens of 291 species belonging to 19 of the 21 genera collected from the Atlantic, Indian and Pacific oceans). Using this information, we confirm the validity of most genera, proposing new ones in cases where the genetic analyses are compatible with morphological characters. Four well-defined munidid clades were recovered, suggesting that new genera should be erected in the currently recognised Munididae (three for the genus Agononida and eleven in Munida), and the genus Grimothea is resurrected. A key to all genera of the family is presented. Molecular clock estimates and ancestral biogeographic area reconstructions complement the taxonomic profiles and suggest some explosive diversification within Munididae during the Cretaceous and the Palaeogene. Further anagenetic events and narrow sympatry accounting for changes in distribution indicate a more limited dispersal capacity than previously considered. Our study unravels how diversification may occur in deep waters and further highlights the importance of the integrative approach in accurately delineating species in understanding the history of a family and the factors driving the evolution.