Zygochlamys patagonica epibionts in deep waters, SW Atlantic Ocean

SCHEJTER LAURA; LÓPEZ GAPPA, JUAN; BREMEC CLAUDIA

Florianopolis

Workshop; 19th. International Pectinid Workshop; 2013

In southern SW Atlantic, the continental slope shows many recognized submarine canyons, varying in depth and extension. The Argentinean continental slope is cut by multiple deep submarine canyons and channels crossing the upper continental slope in a W-E direction, organised in two submarine canyon systems, the Ameghino and the Patagonia (or Almirante Brown) systems (Ewing et al. 1964, Lastras et al. 2011). Recent studies were focused on megafauna living near canyon areas outside the Argentinean shelf break (Portela et al., 2012), while within one of the canyons (43º35'S - 59º33'W, 325 m depth), the only available information refers to the general composition of the benthic invertebrate community (Bremec and Schejter, 2010) and to taxonomy of sponges collected as part of the assemblage (Bertolino et al., 2007). In this deep habitat, the Patagonian scallop contributed with nearly 20% of the total biomass, and taxa richness inside canyon, which remained undisturbed, was higher than in the surrounding fishing grounds. It is well known that most basibiont species are found in larger hard shelled molluscs and crustaceans (Wahl 2009), which, in different habitats or regions, often feature different epibiotic species or different degrees of epibiotic coverage (Reiss et al. 2003, Dougherty and Russell 2005, Wahl 2009). In order to update information, we studied the epibiotic species settled on Patagonian scallops collected from a submarine canyon at the Argentinean continental margin. Material and methods The benthic fauna was collected with a 2.5 m mouth opening dredge, 10mm mesh size, in a submarine canyon detected in April 2005 by means of a multibeam SIMRAD EM1002 sonar, and located at 43º35'S - 59º33'W, 325 m depth. We sampled 103 Patagonian scallops Zygochlamys patagonica (King, 1832) ranging from 22 to 69 mm total shell height, which were carefully preserved and studied under a binocular microscope for the identification of epibionts. Presence-absence data of all epibionts were registered on both valves. Results and discussion We found 53 epibiotic taxa on living Patagonian scallops in deep waters. Bryozoa were represented by 34 species, followed by Cnidaria (5 species), Polychaeta and Porifera (4 species each), Ascidiacea (2 taxa), Crustacea, Bivalvia and Brachiopoda (1 species each) and Foraminifera. Bryozoa richness registered on Z. patagonica during this study (34) was higher than the value reported for scallop fishing grounds distributed in shelf-break frontal areas along the 100m isobaths, where the group was represented by 22 taxa (López Gappa and Landoni, 2009. Although the group is dominant in terms of species richness, only 15 of the species recorded in the deep location were previously registered as epibionts of scallops in commercial beds located at the Argentinean continental shelf. The most frequent epibionts recorded were the bryozoans Osthimosia eatonensis (Busk, 1881) and Arachnopusia monoceros (Busk, 1854), the polychaetes Serpula narconensis (Baird, 1865), Idanthyrsus macropalea (Schmarda, 1861) and Serpulinae. We registered for the first time seventeen species of Bryozoa, three different species of Cnidaria: Stylasteridae (2 species) and Clavulariidae colonies, two species of Porifera (Tedania spp.) and the Brachiopoda Lyothyrella uva, encrusting the valves of the Patagonian scallop. In the case of bryozoans and the brachiopod, all the species are commonly found in the Magellanic Biogeographic Province associated to Malvinas Current (Roux and Bremec, 1996; López Gappa, 2000). The species Tedania (Tedaniopsis) infundibuliformis was previously registered in Chilean Pacific waters (Desqueyroux-Faúndez and Van Soest, 1996) and this constitutes a new record for the SW Atlantic Ocean. Bibliography Bertolino M., Schejter L., Calcinai B., Cerrano C., Bremec C. 2007. Porifera Research: Biodiversity, Innovation and Sustainability, Custódio Marcio R., Hajdu Eduardo, Lobo-Hajdu Gisele, Muricy Guilher (Eds.). Proceed. 7º Int. Sponge Symposium, Buzios, Brasil, 189-201. Bremec C., Schejter L. 2010. Rev. Chilena Hist. Nat. 83: 453-457. Desqueyroux-Faúndez R, Van Soest R.1996. Rev. Suisse Zool. 103: 3-79. Dougherty J., Russell M. 2005. J. Shellfish Res. 24: 35-46. Ewing M., Ludwig W., Ewing J. 1964. J. Geophys. Res. 69: 2003-2032. Lastras G., Acosta J., Muñoz A., Canals M. 2011. Geomorphology 128: 116-136. López Gappa J. 2000. Div. Distr. 6: 15-27. López Gappa J., Landoni N. 2009. Sci. Mar. 73: 161-171. Portela J. et al. 2012. Marine Ecosystems, Antonin Cruzado (Ed.), InTech, pp. 199-228. Roux A., Bremec C. 1996. Rev. Invest. Des. Pesq. 10: 109-114. Reiss H., Knauper S., Kröncke I. 2003. Sarsia 88: 404-414. Schejter L., Bremec C. 2007. J. Mar. Biol. Ass. U.K. 87: 917-925. Wahl M. 2009. Marine Hard Bottom Communities, Ecological Studies 206, M. Wahl (Ed.): 61-72. Financial support: PICT 2008-1119, PIP 2010-2012 No. 0291, IAI CRN 3070, CONICET, INIDEP.