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This paper provides updated taxonomic knowledge about hydrozoan species and provides ecological information including geographical and bathymetric distributions and biological substrata for the various hydroid assemblages from the Sub‐Antarctic Biogeographical Region, mainly Buenos Aires and the Uruguayan coasts. Five of the 41 species found are new records for the study region. Thirty‐one species (75.6%), all found at depths of less than 80 m, have cosmopolitan distributions. Biodiversity decreased markedly below 80 m depth, where nine species (≈22%) distributed in the Southern hemisphere and one endemic species (2.4%) were found. Most species were non‐specific epizoites, occurring on diverse substrata. A non‐parametric multivariate similarity analysis revealed nine species groups that were correlated with large‐scale and local oceanographic patterns and with the availability of suitable substrata. The main hydroid substrata for eight of the groups were cnidarians, molluscs (mainly blue mussels), quartzite rocks and sponges. In a single group found in Patagonian scallop beds, the main biological substrata were polychaete tubes, other hydroids and scallops.

The diet of Dipturus chilensis was composed mainly of the nototheniid fish Patagonotothen ramsayi, squid Illex argentinus, hake Merluccius hubbsi, serolid isopods, and crustaceans. Our results suggest that D. chilensis feeds selectively on some teleosts and rejects eel-like fishes. Total length of consumed P. ramsayi was significantly correlated with the skate's mouth width.

The first open-sea (non-coastal) Marine Protected Area (MPA) in Argentina was created in 2013 (and named ''Namuncurá''), at Burdwood Bank, an undersea plateau located about 200 km south from Malvinas/Falkland Islands, SW Atlantic Ocean. This contribution represents the most recent and complete checklist of benthic organisms (mainly mega and macrofauna) that summarized 240 taxa collected at three sites in the mentioned area. The benthic richness here documented largely exceeds the values coming from other productive areas in Argentinean waters. Faunistic composition was different among the sites, although several species were shared. Bryozoans presented the highest richness compared to the other groups, followed by mollusks and sponges. These data represent valuable information and a very helpful starting point for incoming research, conservation efforts and management. It is essential to establish the spatial distribution of indicator taxa, like corals, sponges and bryozoans, to better attempt at the protection of benthic biodiversity in this rich Argentinean marine system. This is a key issue considering the notable extension of the MPA compared to other areas in Argentina, the bathymetric variations, particular oceanographic conditions and different fishing circumstances within the area.

SUMMARY: The present paper analyses the diet, feeding strategy and niche width of B. macloviana in a sector of the Argentinean Continental Shelf (ACS). Individuals (n = 147) were collected from 43 sampling stations in late summer and autumn 2001. Thirty one alimentary items in the gut contents were found, with a clear dominance of polychaetes. Crustaceans were secondary alimentary items. The polychaete Travisia kerguelensis was the main food item ingested, followed by Nepthyidae, Sabellidae and Lumbrineridae, while Gammaridae and Cirolanidae were the main items among crustaceans. The niche width and feeding strategy displayed by B. macloviana support the specialisation towards polychaetes throughout this study. Slow motile and infaunal species constitute major preys. The results suggest that this skate actively selects worms, reflecting, in some sense, the composition of the polychaete assemblage, and allowing a low dietary overlap with other sympatric skates of the ACS.Keywords: skates, feeding strategy, polychaetes, niche width, specialist, Argentina. RESUMEN: ECOLOGÍA ALIMENTARIA DE BATHYRAJA MACLOVIANA (RAJIFORMES, ARHYNCHOBATIDAE): UNA RAYA CONSUMIDORA DE POLIQUETOS DEL ATLÁNTICO SUDOCCIDENTAL. -En el presente trabajo se analiza la dieta, estrategia alimentaria y amplitud del nicho trófico de Bathyraja macloviana en un sector de la Plataforma Continental Argentina (ACS). Los individuos (n = 147), fueron colectados en 43 estaciones de muestreo a fines de verano y otoño de 2001. Fueron encontrados 31 ítems en los contenidos estomacales con una clara dominancia de poliquetos. Los crustáceos constituyeron ítems secundarios. El poliqueto Travisia kerguelensis fue el principal ítem consumido seguido por Nepthyidae, Sabellidae y Lumbrineridae, mientras que Gammaridea y Cirolanidae fueron los ítems principales entre los crustáceos. En este estudio, la amplitud de nicho y la estrategia alimentaria de esta especie muestran su especialización hacia poliquetos. Especies de baja motilidad e infaunales constituyeron las presas fundamentales. Los resultados sugieren que esta raya selecciona activamente poliquetos, reflejando de algún modo las asociaciones de poliquetos, lo que permite un bajo solapamiento con otras especies de rayas simpátricas del Atlántico Sudoccidental.Palabras clave: rayas, estrategia alimentaria, poliquetos, amplitud de nicho, especialista, Argentina.

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