Decapod Crustacean Assemblages Research Articles

Decapod Crustacean Records from A Collection of Marine Soft-Bottom Macrofauna of the Italian Waters Supporting the Update of Checklists and Registers of the Mediterranean Basin

Decapod crustaceans are important components of the fauna of soft-bottom habitats. In this work, the records of decapod crustaceans are provided through the analysis of a large soft-bottom benthic macroinvertebrates dataset of the Central Mediterranean Sea. Decapod crustacean assemblages were collected in the last twenty years by a Van Veen grab in 42 study sites located along the Italian coasts at depths ranging from 1 up to 120 m. The spatial distribution of the crustaceans examined, which include 120 species belonging to 40 families, was investigated according to the biogeographical zones identified in the Italian seas. The spatial distribution of 36 species was updated, comparing the ISPRA decapod crustacean dataset with the most recent Italian checklists. For the species updated, the number of specimens, the year and season of sampling, and environmental data, such as the bathymetric range and habitat details, are provided for each site investigated. Data are discussed and compared with the existing literature, also referring to what is reported in the World Register of Marine Species (WoRMS), with the aim of contributing to the knowledge of the biodiversity of the marine species and supporting the updating of checklists and registers in the Mediterranean Basin.

A new mid-Cretaceous hermit crab (Crustacea, Anomura) from Central Russia sheds new light on paguroid evolution

Paguroid anomurans constitute a large portion of modern-day decapod crustacean assemblages in all oceans and seas across the globe. However, their palaeontological record is still rather patchy, which partly explains why their phylogeny remains poorly understood. A newly collected specimen of an extinct paguroid is here shown to have a major impact on the evolutionary history of this group of anomurans. A new genus and species, Mutotylaspis tripudium, are here erected to accommodate a well-preserved, extraordinarily crab-like hermit crab from the lower Albian (mid-Cretaceous) of Vladimir Oblast (Central Russia) that appears closely related to the extant enigmatic deep-sea taxon Tylaspis anomala Henderson, 1885, as well as to other members of the extant family Probeebeidae Boone, 1926. Ongoing palaeontological research during the last two decades has provided ample evidence that paguroid evolution was much more intricate and complex than gleaned solely from extant hermit crabs. The newly collected specimen named herein is the first fossil member of the family Probeebeidae and constitutes an additional key species for unravelling paguroid evolution and extending the stratigraphical range of the family downwards into the mid-Cretaceous.

An Aptian sponge-associated decapod crustacean assemblage from Cal Cassanyes (Catalonia, north-east Iberian Peninsula): Taxonomy and palaeoecological implications

A highly diverse decapod crustacean fauna is described from the classic Aptian outcrop of Cal Cassanyes (Castellet i la Gornal) in Catalonia. Although decapod crustaceans are a minor component of the rich invertebrate assemblages at that locality, the just over fifty specimens collected comprise sixteen taxa assignable to the Macrura, Anomura and Brachyura. Of these, the last-named are the most prominent group, comprising eleven species, representing seven families, inclusive of one representative of the Eubrachyura. On the basis of this material, two new genera and five new species are erected, namely Pagurus? garrafensis sp. nov., Garrafosopon gen. nov. angustus (Wright and Collins, 1972) comb. nov., Vectis blesai sp. nov., Mesodromilites prietoi sp. nov., Necrocarcinus mariae sp. nov. and Iberodorippe vinea gen. nov., sp. nov. In addition, Hoploparia sp., an indeterminate axiid and one paguroid, as well as one indeterminate galatheoid are recorded here. Material of Distefania incerta (Bell, 1863), the commonest species at the study site by far, of Goniodromites laevis (Van Straelen, 1940) and of Etyxanthosia fossa (Wright and Collins, 1972) represents the first Aptian and stratigraphically oldest records for these taxa. Added to this list are also Eodromites sp., Paranecrocarcinus? sp. and Pseudonecrocarcinus? sp. The high decapod crustacean diversity at Cal Cassanyes establishes this locality as the richest Aptian assemblage from the Iberian Peninsula, but also one of the richest in the world. The faunal assemblages here are dominated by sponges, and the varied composition of the decapod crustacean faunas can be linked to upwelling currents which provided abundant nutrients. In fact, the establishment of sponge communities played a crucial role in activating the food chain and functioned similarly to a patch reef, creating a relatively sheltered environment that facilitated the colonisation of other invertebrate communities, including decapod crustaceans. The latter occupied various trophic levels as both primary and secondary consumers. Current knowledge of Early Cretaceous decapod crustaceans is scant and hinders a thorough palaeobiogeographical analysis. The present study emphasises the challenges surrounding the identification of endemic taxa, thus impacting our understanding of decapod crustacean palaeobiogeography of the late Early Cretaceous.

Decapod crustacean assemblages on trawlable grounds in the northern Alboran Sea and Gulf of Vera

This study analyses the samples collected annually (2012 to 2018) on circalittoral and bathyal soft bottoms (30 to 800 m) by the MEDITS surveys in the northern Alboran Sea (including Alboran Island) and the Gulf of Vera to determine the composition, structure and distribution of decapod crustacean assemblages. A total of 94 decapod crustacean species were identified. Non-metric multidimensional scaling showed depth to be the main factor for distinguishing four main decapod assemblages: the inner shelf (30-100 m depth), outer shelf (101-200 m), upper slope (201-500 m) and middle slope (501-800 m). PERMANOVA analyses revealed further significant depth-related differences between three established geographical sectors of the study area (northern Alboran Sea, Gulf of Vera and Alboran Island). Generalized additive model analyses were used to assess the bathymetrical, geographical and environmental effects on the ecological indices of each assemblage. Results showed that depth and the geographical effect were the main drivers in all cases. Decreases in abundance and increases in species richness, Shannon-Wiener diversity and Pielou’s evenness indices with depth were detected. This study shows the primacy of depth and geographical effect on the distribution of decapod species in the study area, in alignment with findings from other parts of the Mediterranean Sea.

Decapod crustaceans from the lower Miocene Qom Formation of the Isfahan area, Central Iran

From the lower Miocene (Burdigalian) of the Qom Formation, exposed in three sections (Kuh-e-Donbeh, Bagher-Abad, and Vartun) in Central Iran, a deca-pod crustacean assemblage is described. The specimens exhibit two modes of preservation: carapaces (either isolated or with attached appendages) and isolated cheliped elements. All studied specimens are fractured and/or eroded. Based on this moderately preserved material, three brachyuran crab taxa are identified, including Mursia cf. lienharti (Bachmayer, 1962), Palaeocarpilius rugifer Stoliczka, 1871, and Necronectes sp. The occurrence of P. rugifer represents the youngest confirmed occurrence of the species, whereas other two taxa represent the first confirmed Iranian occurrences of respec-tive genera. This report enriches our knowledge on Miocene decapod assemblages of Iran, and thus helping to better understand the decapod migratory patterns along the Tethyan Sea-way.

Systematics and distribution of decapod crustaceans associated with late Eocene coral buildups from the southern Pyrenees (Spain)

A new decapod crustacean assemblage associated with late Eocene coral reef deposits in northeast Spain (southern Pyrenees) is recorded; it includes Gemmellarocarcinus riglosensis sp. nov., Daira corallina sp. nov., Lobogalenopsis joei sp. nov., Liopsalis cf. anodon (Bittner, 1875) and Galenopsis crassifrons A. Milne- Edwards, 1865. The genera Gemmellarocarcinus, Daira and Lobogalenopsis are here recorded for the first time from Eocene strata of the Iberian Peninsula, extending their palaeobiogeographical distribution. Detailed sampling from three different coral reef facies within the La Peña buildup, here referred to as branching, tabular and massive, suggest that the core of the reef, which was dominated by branching corals, hosted the highest diversity and abundance of decapod crustaceans. Daira corallina sp. nov. predominated in the branching corals facies, while G. crassiforns was the most abundant taxon within the tabular coral facies and carpiliids showed preferences for environments with massive corals. Thus, this constitutes a good example of primary ecological zonation among decapod crustaceans within a discrete reef.

Oyster Reefs in Northern Gulf of Mexico Estuaries Harbor Diverse Fish and Decapod Crustacean Assemblages: A Meta-Synthesis

Oyster reefs provide habitat for numerous fish and decapod crustacean species that mediate ecosystem functioning and support vibrant fisheries. Recent focus on the restoration of eastern oyster (Crassostrea virginica) reefs stems from this role as a critical ecosystem engineer. Within the shallow estuaries of the northern Gulf of Mexico (nGoM), the eastern oyster is the dominant reef building organism. This study synthesizes data on fish and decapod crustacean occupancy of oyster reefs across nGoM with the goal of providing management and restoration benchmarks, something that is currently lacking for the region. Relevant data from 23 studies were identified, representing data from all five U.S. nGoM states over the last 28 years. Cumulatively, these studies documented over 120,000 individuals from 115 fish and 41 decapod crustacean species. Densities as high as 2800 ind m-2 were reported, with individual reef assemblages composed of as many as 52 species. Small, cryptic organisms that occupy interstitial spaces within the reefs, and sampled using trays, were found at an average density of 647 and 20 ind m-2 for decapod crustaceans (range: 18 - 2843) and fishes (range: 2 - 56), respectively. Both groups of organisms were comprised, on average, of 8 species (range: 3 - 15). Larger-bodied fishes captured adjacent to the reef using gill nets were found at an average density of 6 ind m-2 (range: 1- 68) which came from 23 species (range: 9 - 46). Decapod crustaceans sampled with gill nets had a much lower average density, < 1 ind m-2, and only contained 2 species. On average, seines captured the greatest number of fish species (n = 33), which were made up of both facultative residents and transients. These data provide general gear-specific benchmarks, based on values currently found in the region, to assist managers in assessing nekton occupancy of oyster reefs, and assessing trends or changes in status of oyster reef associated nekton support. More explicit reef descriptions (e.g., rugosity, height, area, adjacent habitat) would allow for more precise benchmarks as these factors are important in determining nekton assemblages, and sampling efficiency.

Middle Miocene decapod crustacean assemblage from the Tuzla Basin (Tušanj, Bosnia and Herzegovina), with a description of two new species and comparison with coeval faunas from Slovenia

Middle Miocene decapod crustacean assemblage from the Tuzla Basin (Tušanj, Bosnia and Herzegovina), with a description of two new species and comparison with coeval faunas from Slovenia

Exploration of the Canyon-Incised Continental Margin of the Northeastern United States Reveals Dynamic Habitats and Diverse Communities.

The continental margin off the northeastern United States (NEUS) contains numerous, topographically complex features that increase habitat heterogeneity across the region. However, the majority of these rugged features have never been surveyed, particularly using direct observations. During summer 2013, 31 Remotely-Operated Vehicle (ROV) dives were conducted from 494 to 3271 m depth across a variety of seafloor features to document communities and to infer geological processes that produced such features. The ROV surveyed six broad-scale habitat features, consisting of shelf-breaching canyons, slope-sourced canyons, inter-canyon areas, open-slope/landslide-scar areas, hydrocarbon seeps, and Mytilus Seamount. Four previously unknown chemosynthetic communities dominated by Bathymodiolus mussels were documented. Seafloor methane hydrate was observed at two seep sites. Multivariate analyses indicated that depth and broad-scale habitat significantly influenced megafaunal coral (58 taxa), demersal fish (69 taxa), and decapod crustacean (34 taxa) assemblages. Species richness of fishes and crustaceans significantly declined with depth, while there was no relationship between coral richness and depth. Turnover in assemblage structure occurred on the middle to lower slope at the approximate boundaries of water masses found previously in the region. Coral species richness was also an important variable explaining variation in fish and crustacean assemblages. Coral diversity may serve as an indicator of habitat suitability and variation in available niche diversity for these taxonomic groups. Our surveys added 24 putative coral species and three fishes to the known regional fauna, including the black coral Telopathes magna, the octocoral Metallogorgia melanotrichos and the fishes Gaidropsarus argentatus, Guttigadus latifrons, and Lepidion guentheri. Marine litter was observed on 81% of the dives, with at least 12 coral colonies entangled in debris. While initial exploration revealed the NEUS region to be both geologically dynamic and biologically diverse, further research into the abiotic conditions and the biotic interactions that influence species abundance and distribution is needed.

Taxonomy and palaeoecology of a decapod crustacean assemblage from the Oxfordian of Stránská skála (Southern Moravia, Czech Republic)

Taxonomy and palaeoecology of a decapod crustacean assemblage from the Oxfordian of Stránská skála (Southern Moravia, Czech Republic)

New decapod crustacean assemblage from the Upper Cretaceous (Cenomanian) of Chiapas, Mexico

New decapod crustacean assemblage from the Upper Cretaceous (Cenomanian) of Chiapas, Mexico

Diversity of decapod crustaceans at the interface of unconsolidated seabed areas and rocky shores in tropical/subtropical Brazil

The decapod crustacean assemblages from unconsolidated seabed areas located near rocky shores in the Ubatuba region on the south-east coast of Brazil were analysed by investigating the abundance, richness, diversity and dominance of species. The relationships of the sediment and bottom-water temperature to total species abundance, richness and diversity were also evaluated. Monthly samples were taken from January 1998 through December 1999 at sites in Ubatumirim and Mar Virado. At each locality, three areas were defined as either ‘exposed’, ‘sheltered’ or ‘island’. The highest species abundance was found in the sheltered area of Ubatumirim and the exposed area of Mar Virado, and during autumn. At Ubatumirim, the highest richness occurred in the exposed area and the highest diversity near the island. At Mar Virado, the highest richness and diversity were found near the island. Autumn and winter collections yielded the highest richness but the lowest diversity. The higher diversities, which were measured near the islands and during spring and summer, were consequences of the greater evenness of the data. The areas with the highest diversity also had the most heterogeneous sediment composition, thus reinforcing the hypothesis that areas with more complex substrata support more diverse faunas.

Succession of fish and crustacean assemblages following reinstatement of tidal flow in a temperate coastal wetland

Fish and decapod crustacean assemblages were sampled from two manipulated creeks in which tidal flow had been increased through culvert removal. Assemblages were compared to those of two control creeks where culverts remained and two reference creeks without culverts. The presence of culverts reduced the richness and abundance of estuarine–marine dwelling species. Successional changes over a 16 year period (2 years prior to culvert removal and 14 years after) showed an immediate response at one manipulated creek but many years to attain reference condition. The other manipulated creek showed a completely different trajectory: oscillation between control and reference status with no clear intermediary condition. We concur with other investigators that short-term studies may give only a partial indication of response to rehabilitation efforts in coastal wetlands and longer-term studies (5–10 years) are recommended. There is some evidence that over longer-time frames, the presence of distinct groups of fish and/or decapods may indicate stages in the maturation of a rehabilitated wetland.

Impact of hard-bottom substrata on the small-scale distribution of fish and decapods in shallow subtidal temperate waters

The micro-scale spatial distribution patterns of a demersal fish and decapod crustacean assemblage were assessed in a hard-bottom kelp environment in the southern North Sea. Using quadrats along line transects, we assessed the in situ fish and crustacean abundance in relation to substratum types (rock, cobbles and large pebbles) and the density of algae. Six fish and four crustacean species were abundant, with Ctenolabrus rupestris clearly dominating the fish community and Galathea squamifera dominating the crustacean community. Differences in the substratum types had an even stronger effect on the micro-scale distribution than the density of the dominating algae species. Kelp had a negative effect on the fish abundances, with significantly lower average densities in kelp beds compared with adjacent open areas. Averaged over all of the substrata, the most attractive substratum for the fish was large pebbles. In contrast, crustaceans did not show a specific substratum affinity. The results clearly indicate that, similar to other complex systems, significant micro-scale species–habitat associations occur in northern hard-bottom environments. However, because of the frequently harsh environmental conditions, these habitats are mainly sampled from ships with sampling gear, and the resulting data cannot be used to resolve small-scale species–habitat associations. A detailed substratum classification and community assessment, often only possible using SCUBA diving, is therefore important to reach a better understanding of the functional relationships between species and their environment in northern temperate waters, knowledge that is very important with respect to the increasing environmental pressure caused by global climate change.

The decapod community from the Early Pliocene (Zanclean) of “La Serra” quarry (San Miniato, Pisa, Toscana, central Italy): sedimentology, systematics, and palaeoenvironmental implications

We report an unusual and rich decapod crustacean assemblage from the early Pliocene (Zanclean), recently collected during the excavations of the “La Serra” quarry, located in La Serra, near San Miniato, Pisa (Toscana, central Italy). The studied specimens have been assigned, as follows: Axius sp., Callianassa chalmasiiBrocchi, 1883, and Calliaxina cf. C. punica (de Saint Laurent and Manning, 1982) (infraorder Axiidea de Saint Laurent, 1979); Gebiacantha tuscia Garassino, Pasini, De Angeli and Charbonnier sp. nov. (infraorder Gebiidea de Saint Laurent, 1979); Pagurus alatusFabricius, 1775, and Pagurus sp. (infraorder Anomura MacLeay, 1838); Dromia neogenicaMüller, 1978, Dromia sp., Medorippe cf. M. ampla Garassino, De Angeli, Gallo and Pasini, 2004, Ilia nucleus (Linnaeus, 1758), Ristoria pliocaenica (Ristori, 1891), Pisa armata (Latreille, 1803), Macropodia sp., Maja squinado (Herbst, 1788), Derilambrus angulifrons (Latreille, 1825), Atelecyclus undecimdentatus (Herbst, 1783), Liocarcinus sp., Thalamita italica Garassino, Pasini, De Angeli and Charbonnier sp. nov., Pilumnus cf. P. hirtellus (Linnaeus, 1761), Eriphia cocchiiRistori, 1886, Goneplax rhomboides (Linnaeus, 1758), Goneplax sacciCrema, 1895, (infraorder Brachyura Linnaeus, 1758). Moreover, two specimens have been assigned to callianassideans sensu lato and 13 specimens to indeterminate axiideans. CalliaxinaNgoc-Ho, 2003, GebiacanthaNgoc-Ho, 1989, Ristoria Garassino, Pasini, De Angeli and Charbonnier gen. nov., and Macropodia Leach, 1814, are reported for the first time in the fossil record and the extant Pagurus alatus, Ilia nucleus, Pisa armata, Derilambrus angulifrons, and Pilumnus cf. P. hirtellus, are reported in the fossil record from the Pliocene. Everywhere “La Serra” quarry bio-community is very important, representing one of the richest and most diversified crustacean faunas from the Pliocene reported to date in the Mediterranean basin and worldwide, increasing notably the knowledge on the decapod populations and distribution during the early Pliocene. This community is indicative of a palaeoenvironment of shallow sublittoral water, with sandy-muddy and alternate hard shell bottom, partially covered or in proximity of seagrass, similar to the extant Mediterranean Posidonia beds, mainly inhabited by fossorial and benthonic decapods.

Long-term changes in the composition and diversity of deep-slope megabenthos and trophic webs off Catalonia (western Mediterranean): Are trends related to climatic oscillations?

For depths ranging between 650 and 1700 m we have compared recent (2007–2008) to older (from 1988 to 1992) data, searching for long-term changes in the distribution, abundance and composition of deep megafauna (fish and decapods) off the central Catalonian coasts (western Mediterranean). Overall, in the depth interval between 600 and 1100 m, we found higher abundance of fish in 1988–1992 than in 2007, a decrease simultaneous with an increase of decapod crustaceans. Older and more recent haul replicates (after 20 years) had similar assemblage composition in the depth range 1300–1700 m, whereas we found significant changes at 1000 m. Diversity of fish was greater in 1988–1992 than in 2007, while diversity of decapod crustaceans increased between the two periods. Thus, there was a reorganization in benthopelagic communities, rather than a loss of biodiversity. This was in agreement with long-term changes described for diversity of (neritic) zooplankton in the western Mediterranean. We found a dominance of plankton-suprabenthos feeders (e.g. fish such as Lepidion lepidion, Hymenocephalus italicus and Alepocephalus rostratus; the decapods Plesionika spp. and Sergestes arcticus) in 1988–1992. In 2007 by contrast, dominance of plankton-suprabenthos feeders decreased, and assemblages were increasingly composed of benthos-feeding decapods (e.g. Aristeus antennatus, Pontophilus norvegicus and some hermit crabs) preying for instance on polychaetes. These results coincided with low/negative North Atlantic Oscillation index (NAO) in 2007 and in the period immediately before (2004–2006) 2007 (increase of benthos feeders), and with high average NAO in 1988–1992 (decrease of benthos feeders, which in turn may enhance abundance of plankton feeders). The benthic decapod Calocaris macandreae and suprabenthos (small crustaceans, mostly peracarids, living on and just beneath the sediment surface) are key prey in food webs off Catalonian margins, acting as links between surface oceanographic processes and abundance of benthopelagic predators. A conceptual model is presented relating changes in climatic conditions with changes in deep-sea, benthic-suprabenthic food webs. Calocari macandreae was more abundant in 2007, after 3 years of negative NAO. Under negative/low NAO, rainfall and river discharges increase in the NW Mediterranean, which may enhance advective food inputs for macrobenthos. This fits well with the higher abundance of benthos feeders in 2007, as well as with the significant deepening of decapod crustacean assemblages in that same period. Suprabenthos, being short-lived and annual species, were more abundant under positive NAO conditions (1988–1992), probably enhancing the abundance or aggregation of suprabenthic/pelagic feeders.

Decapod crustacean assemblages from littoral bottoms of the Alborán Sea (Spain, west Mediterranean Sea): spatial and temporal variability

The structure of decapod crustacean assemblages living in shallow waters (5 to 25 m depth) in an area of the Alboran Sea (Mediterranean Sea) neighbouring the Strait of Gibraltar was studied. The relatively high richness found in this area is probably due to the diversity of substrata and the confluence of Atlantic and Mediterranean waters. The most abundant species was the hermit crab Diogenes pugilator due to the prevalence of sandy substrate, the shallow depth-range, and the species’ life history. The coralligenous bottom showed the highest species richness and diversity values due to the complexity of microhabitats in this type of bottom and probably due to the food flux associated with currents. Conversely, shallow, well calibrated, fine to medium sandy bottoms of 5 m had the lowest values and the maximum densities due to the high abundance of a few well adapted species. The analysis of the different stations showed significant spatial differences according to depth and sedimentary characteristics. Depth is the environmental variable that correlates best with the decapod assemblages, with a particularly significant boundary between 5 m and 15 m. Nevertheless, there was a continuous transition between the assemblages. These results evidence the importance of quantitative studies in differentiating decapod assemblages. Relationships between these assemblages should also be taken into account in coastal management, since altering a substrate could have repercussions for the structure of the communities of neighbouring substrates. No seasonal significant differences were found in the overall analysis of the area, but there were differences between spring and autumn and spring and summer in relation to depth and substrate (crossed analysis). Finally, we present the species which allow us to discriminate the different assemblages according to sediment and depth, as well as the species’ contributions.

Decapod crustacean assemblages off the West coast of central Italy (western Mediterranean)

Community structure and faunal composition of decapod crustaceans off the west coast of central Italy (western Mediterranean) were investigated. Samples were collected during five trawl surveys carried out from June 1996 to June 2000 from 16 to 750 m depth. Multivariate analysis revealed the occurrence of five faunistic assemblages: 1) a strictly coastal community over sandy bottoms at depths Leptometra phalangium facies is found in many areas at depths between 120 and 180 m. The brachyuran crab Liocarcinus depurator dominates the shallow muddy-sandy bottoms of the shelf, while Parapenaeus longirostris is the most abundant species from the shelf to the upper slope assemblage. The dominant species on the middle slope are mainly nektobenthic ( Aristeus antennatus , Aristaeomorpha foliacea , Plesionika martia ), bentho-pelagic ( Pasiphaea sivado ) and benthic species ( Nephrops norvegicus ). The average diversity of the five assemblages defined increased with depth and the highest diversity values were found in the slope assemblages. Depth is the main factor influencing decapod assemblage composition, but sediment type and dissolved organic matter seem to be secondary structuring factors particularly in the shelf zone.

서해 함평만 십각 갑각류의 종조성과 계절변동

Species composition and seasonal variation of decapod crustacean assemblage in Hampyeong Bay, Korea were examined. Sampling was monthly made by a shrimp trawl between March 2003 to February 2004. A total of 39 species of 20 families were collected. Of these, Latreutes planirostris, Palaemon gravieri, Parapenaeopsis tenella, Exopalaemon carinicauda, Charybdis japonica, Trachysalambria curvirostris and Palaemon macrodactylus were dominant species comprising of the total number of individuals. Charybdis japonica, P. gravieri, Oratosquilla oratoria, E. carinicauda, T curvirostris, Metapenaeus joyneri and P. tenella represented of the total biomass. While total abundance (number of individuals) was high in spring, total biomass and species richness (number of species) and diversity were high in summer. Cluster analysis, based on monthly abundance data of the 14 most common species, showed that the species were separated into three different groups. Group A composed of Leptochela gracilis, Alpheus japonicus, Crangon uritai, P. macrodactylus, E. carinicauda, P. gravieri, O. oratoria, C. japonica, which were year round residents, group B M. joyneri, T. curvirostris and P. tenella, which were abundant in summer, and group C Crangon hakodatei, Latreutes anoplonyx and L. planirostris, which were abundant in winter. Principal component analysis revealed that seasonal variation in the decapod crustacean assemblage was attributed to the abundance of temporal species such as penaeid shrimps, which were abundant in summer, due to seasonal variation of water temperature and reproductive pattern.

Benthic decapod crustaceans associated with captures of &lt;i&gt;Munida&lt;/i&gt; spp. (Decapoda: Anomura) in the Beagle Channel, Argentina

Benthic decapod crustacean assemblages in the Beagle Channel are dominated by the galatheid crabs Munidasubrugosa and Munida gregaria. This study deals with the bathymetric and spatial distribution, density and diversity of the assemblage of decapod species that co-occur with Munida spp. in the Beagle Channel. A total of 131 samples were obtained using an epibenthic trawl from February 1999 to December 2000. They were taken monthly from two depth strata separated by the 40 m isobath (range: 4-262 m), and from three different sites: Bahia Lapataia, Ushuaia and Punta Segunda. Sixteen of the 36 recorded species of decapod crustaceans from the Beagle Channel were caught. Munidasubrugosa and M. gregaria contributed 94% to the total decapod material. Of the remaining 6%, Austropandalusgrayi (Caridea) was the most abundant species, constituting 43% of the non-galatheid decapod fraction. Some species, namely Paguruscomptus and Eurypodius spp., were characteristic of shallow waters ( 40 m). The average density and diversity of non-galatheid decapods varied with depth and location. Decapod diversity correlated positively with the density of algae and polychaete tubes. The influence of three-dimensional bottom structure on decapod diversity in the Beagle Channel is discussed.