Hermit crabs (Decapoda: Crustacea) from deep Mauritanian waters (NW Africa) with the description of a new species

De Matos-Pita, Susana S., Ramil, Fran (2015): Hermit crabs (Decapoda: Crustacea) from deep Mauritanian waters (NW Africa) with the description of a new species. Zootaxa 3926 (2): 151-190, DOI: http://dx.doi.org/10.11646/zootaxa.3926.2.

Decapod assemblages in deep Mauritanian waters

Crustacean decapods are amongst the dominant groups of megabenthic invertebrates in the Atlantic continental shelf and slope. Although studies on West African decapod fauna are numerous, knowledge on their communities is scarce and focussed in Namibian (Macpherson, 1991), South African (Kensley, 2006) and Guinea-Bissauan (Muñoz et al. 2012) waters. However, nothing is currently known on the structure and composition of the crustacean decapod assemblages off Mauritania. Between 2007 and 2010 the Spanish Institute of Oceanography (IEO) carried out four annual multidisciplinary surveys of one month’s duration in Mauritanian waters, from Cape Blanc to the Senegal River. Conducted in collaboration with the Mauritanian Institute for Oceanographic Research and Fisheries (IMROP) and the University of Vigo (Spain), these surveys were part of a larger programme (ECOAFRIK) focussing on the study of the biodiversity of African benthic ecosystems. Maurit- 0911 and Maurit- 1011 surveys sampled five transects perpendicular to the coast at five bathymetric strata using an Agassiz trawl. We identified a total of 77 decapod species belonging to 36 families. Brachyura was the richest group, with 28 species, followed by Caridea (21 spp.), Anomura (14 spp.), Dendrobranchyata (10 spp.) and Reptantia (6 spp.). The most diverse families were Paguridae, Pandalidae, Inachidae and Pasiphaeidae (with 6-5 spp. each). We defined four bathymetric main assemblages: continental shelf (<150 m), break shelf and upper slope (150–300 m), middle slope (500 m) and deep slope (1000–1500 m). Mean species richness decreased with depth from deep shelf to slope (16 to 4 species), while the highest abundance and biomass were found in the break shelf and upper slope. Although the Pielou’s evenness index peaked in the deepest strata (>500 m), no clear pattern was observed for the Shannon- Wiener diversity index. The maximum similarity value (47.6%) corresponded to the shelf assemblage due to the abundance of three brachyuran species: Calappa pelii, Inachus angolensis and Solenolambrus noordendei. As expected, absolute dissimilarity (100%) was found between the shelf and deep slope assemblages. Identifying the main features (distribution, structure and composition) of the decapods’communities is a key issue to assess the effects of the trawling pressure on them in Mauritanian fishing grounds. References Kensley B (2006) Pelagic shrimp (Crustacea: Decapoda) from the shelf and oceanic waters in the southeastern Atlantic Ocean off South Africa. Proceed Biol Soc Washington 119: 384–394. Macpherson E (1991) Biogeography and community structure of the decapod crustacean fauna off Namibia (Southeast Atlantic). Journ Crust Biol 11, 401–415. Muñoz I, García-Isarch E, Sobrino I, Burgos C, Funny R and González-Porto M (2012) Distribution, abundance and assemblages of decapod crustaceans in waters off Guinea-Bissau (north-west Africa). Journ Mar Biol Ass UK 92(3): 475-494.MAVA (contract 12/87 AO C4/2012

Contribution to the knowledge of the deep brachyuran fauna (Crustacea: Decapoda) in waters off Mauritania (NW Africa)

Four multidisciplinary oceanographic surveys were conducted in November and December from 2007 to 2010, along the Mauritanian coast (NW Africa). A total of 10,514 brachyuran crabs belonging to 33 species were captured in 316 hauls at depths between 79 and 1867 m. The most specious family was Inachidae represented by nine species; the remaining 24 species belonged to 16 other brachyuran families. Monodaeus cristulatus is reported for the first time since its original description. Seven other species, Ethusa rugulosa, Pseudomyra mbizi, Inachus grallator, Macropodia gilsoni, Macropodia hesperiae, Solenolambrus noordendei and Spinolambrus notialis extend their range of distribution northwards and, together with Goneplax barnardi, are reported here for the first time in Mauritanian waters. New data about depth ranges are reported for Acanthocarpus brevispinis, Ethusa rugulosa, Inachus aguiarii, Inachus grallator, Inachus nanus, Macropodia macrocheles, Solenolambrus noordendei, Spinolambrus notialis, Liocarcinus corrugatus and Monodaeus cristulatus. New data relating to the spawning period for most of the species are also included, as are some biogeographic and bathymetric considerations about brachyurans studied in the area

Decapod assemblages in Mauritanian waters

We studied the decapods collected in four trawling surveys conducted in Mauritanian waters, in 281 hauls performed at depths between 81 and 1825 m, in November–December 2007–2010. A total of 214,982 specimens with a biomass of 1.6 tonnes was captured, Nematocarcinidae being the most abundant family, mainly due to one single species, Nematocarcinus africanus . Parapenaeus longirostris and Glyphus marsupialis were the species that most contributed to the total biomass, while Acanthephyra pelagica was the most common in the studied area. With a total of 118 species, belonging to 39 families , Mauritanian waters are more diverse in decapods than other comparable zones, probably due to the coexistence of tropical and temperate species. Two new species were described and some records increased the geographic range of certain species in the Atlantic . Five main assemblages were identified: shelf (< 100 m), deep shelf-upper slope (100–400 m), deep reef (400–550 m), middle slope (550–1400 m) and deep slope (1400–1800 m). Species of each assemblage are typified. Depth was the main factor structuring the assemblages, along with depth-dependant variables such as bottom temperature, longitude and organic matter content. Latitude also influenced assemblage structure. Greatest abundance and biomass occurred on the deep reef , in relation to minimum oxygen values (1.0–1.3 ml l−1), which may favour the abundance of certain species, such as N. africanus, but negatively affect other species, resulting in a diversity reduction. Diversity generally increased with depth, the highest values being registered on the deep slope

Deep-sea cnidarians of Northwest Africa: Distribution patterns

Cnidarians are one of the most relevant phylum in deep-waters, where Scleractinia, Alcyonacea and Antipatharia may build three-dimensional habitats which host some of the most biodiverse and vulnerable marine ecosystems (‘hot-spots’) along the continental margins. Although ancient expeditions recorded the existence of Lophelia pertusa on the Moroccan, Western Saharan and Mauritanian slopes, the distribution of this cold-water coral and other related vulnerable species in Northwest African is currently unknown. The intensive benthic sampling program developed in the CCLME region from 2002 to 2012 within the framework of the EcoAfrik and FAO EAF-Nansen projects, has allowed to obtain a first insight of the biodiversity and distribution patterns of the cnidarians along the deep-shelf and slope of Northwest Africa. This work analyzes the quantitative data of nine cnidarian taxa (Hydrozoa, Scyphozoa, Alcyonacea, Pennatulacea, Antipatharia, Ceriantharia, Zoantharia, Actiniaria and Scleractinia) collected at 908 trawling stations, carried out between 100 and 1865-m depth, during the 11 research surveys developed onboard R/V Dr. Fridtjof Nansen and R/V Vizconde de Eza in the region. The highest diverse taxa are undoubtedly Hydrozoa (more than 100 species), followed by Alcyonacea and Actiniaria; Zoantharia, Ceriantharia and Scyphozoa showed the lowest values. Our results mainly evidenced that the Saharan and South Moroccan waters were the highest diverse areas, followed by Cape Verde Islands. Diversity values were four times higher northern Cape Blanc than in the tropical area, being Hydrozoa and Alcyonacea the main contributors to the cnidarian diversity in the northern area. Only Actiniaria was the most diverse taxon in the southern part, exhibiting together Zoantharia high biomass values. Antipatharia (black corals) show some relevance only in Cape Verdean and Saharan slopes. The intensive sampling program developed in Northwest Africa will allow the identification and location of areas hosting vulnerable cnidarians, effectively contributing to management and protection of deep-sea ecosystems, mainly in areas which support an intensive fishing exploitation

First record of the deep sea fan species Thesea talismani Grasshoff, 1986 (Anthozoa: Octocorallia: Paramuriceidae) off Mauritania (Northwest Africa)

The sea fan Thesea talismani is a rare deep sea species that was previously only known from the type material, namely one fragment of a colony designated as holotype, which was collected at 956 m depth off Larache (Morocco), and one colony 12 cm height designated as paratype, captured at 888 m off Cap Barbas (Western Sahara) (Grasshoff, 1986). We report here the species for the first time after its original description, based on some specimens captured during the Spanish Maurit surveys and the German cruise MSM16j3, both carried out in waters off Mauritania by the years 2009 and 2010. The samples were collected with a beam trawl and a rock dredge during the Spanish Maurit-0911 and Maurit -1011 surveys, and with a grab, a box corer and also directly with a Remote Operated Vehicle (ROV) during the German cruise MSM16jg. High resolution images, both photography and video recording were also obtained by the ROV. The species was collected between 462 and 1090 m depth and seems associated to coral carbonate mounds and canyon habitats. Our colonies mostly agree with the original description although some intraspeci.fic differences were observed. Most of the colonies match with the type material in size (10-15 cm) and in the ramification pattern with branches up to the second order. In addition, some simple, unbranched colonies were also collected, one of them reaching 30 cm with the distal part devoid of coenenchyme. Sclerite types are similar to those described for the type material although coenenchyme sclerites distribution and abundance vary between the different colonies.MAVA (Contract 12/87 AO C4/2012

Le benthos du CCLME. Bilan des activités de recherche

Benthic ecosystems, mainly those located in shelf and continental margins of African coasts are found among more unknown and slightly studied habitats from our Planet (Decker et al., 2003). The ECOAFRIK project is based on the benthic invertebrate collections and the information gathered in 2147 stations sampled by trawling during the 24 surveys carried out from 2004 to 2012 in shelf and continental margins of Atlantic and Indian African coasts on board R/V Vizconde de Eza and Dr. Fridtjof Nansen. In all these surveys, same methodology have been used and quantitative data sampling of commercial crustacean and cephalopods species, as well as non commercial megabenthic invertebrates, have been planned carefully; in addition, in some surveys specific gear for benthos study have been used, environmental parameters (geomorphologic prospecting with multibeam, sediment samples and oceanographic data) have been taken, and important faunistic collection are preserved. In this presentation are resumed the research and training activities developed in the framework of the CCLME project during the last five years.MAVA (Contract 12/87 AO C4/2012); EAF-NANSEN Mentoring Program (FAO); CCLME-FAO Projec