http://hdl.handle.net/1834/1360 Thu, 23 May 2013 01:22:48 GMT 2013-05-23T01:22:48Z http://hdl.handle.net/1834/1571 Title: Ecological boundaries in estuaries: macrobenthic ß-diversity in the Rio de la Plata system (34-36°S) Authors: Giberto, D.A.; Bremec, C.; Cortelezzi, A.; Rodrigues Capitulo, A.; Brazeiro, A. Abstract: In this study, we analyse spatial patterns of macrobenthic communities of the Río de la Plata system, and assess the species turnover or beta diversity and its relationship with environmental gradients. Macrobenthic samples and physico-chemical parameters were collected from 20 sampling sites along a transect of 560 km, including the freshwater (FW), estuarine (ES)and marine (MA)sectors. Three main assemblages corresponding to the above mentioned sectors were defined with multivariate analysis (cluster, MDS). In total 134 taxa were recorded, 81 in MA, 33 in FW and 38 in ES, represented mainly by polychaete, mollusc and crustacean species. Depth, salinity and clay showed the strongest correlation with the observed faunal patterns (pw=0.62; BIO-ENV analysis). Beta diversity varied between dominant taxonomic groups and was positively correlated with changes in salinity. The high variability in the composition of assemblages was reflected in beta diversity, reaching its highest values at the boundaries between the defined sectors. This study suggests that beta diversity represents a useful tool to define ecological boundaries for benthic communities in the Río de la Plata. Mon, 01 Jan 2007 00:00:00 GMT http://hdl.handle.net/1834/1571 2007-01-01T00:00:00Z http://hdl.handle.net/1834/1815 Title: Epibionts on Flexopecten felipponei (Dall, 1922), an uncommon scallop from Argentina Authors: Schejter, L.; Bremec, C. Abstract: Flexopecten felipponei (Dall, 1922) is a non-commercial, seldom reported pectinid from the SW Atlantic Ocean. In this contribution we review its taxonomy, describe epifaunal species and their levels of encrustation, and discuss the composition of the macrobenthic assemblage where this scallop Iives. Eighteen epibiont taxa were observed to Iive on the valves of these scallops. The most frequent and abundant epibionts on F. felipponei were serpulids, barnacles, and oysters. Although both valves were encrusted, the left valves had higher percentages of coverage. The benthic community contained 69 invertebrate taxa that generally charaeterize other mid-shelf bottorns between 37°S and 39°S. Eight pea crabs of the species Tumidotheres maculatus (Say, 1818)were found inside eight individuals of F. felipponei. Two other scallops had burrows of Polydora websteri Hartman, 1943. These were the first observations of these infestations on F. felipponei. Mon, 01 Jan 2007 00:00:00 GMT http://hdl.handle.net/1834/1815 2007-01-01T00:00:00Z http://hdl.handle.net/1834/1572 Title: The Invasive Rapa Whelk Rapana venosa (Valenciennes 1846): Status and potential ecological impacts in the Rio de la Plata estuary, Argentina-Uruguay Authors: Giberto, D.A.; Bremec, C.; Schejter, L.; Schiariti, A.; Mianzan, H.W.; Acha, E.M. Abstract: Recent range extensions of the invasive rapa whelk Rapana venosa, biological data of the population and possible ecological impacts on the food webs of the Rio de la Plata estuary are presented. A total of 41 rapa whelks and 21 egg capsules were collected between February 2004 and March 2006. Specimens were found all over the mixohaline waters of the estuary, with records off Montevideo, Samborombon Bay and off Punta Rasa. Specimens ranged between 28 and 120 mm shell length. Almost all R. venosa presented epibionts all over the shell, suggesting an exposed lifestyle. Egg-masses were attached to specimens of R. venosa, debris and plastic garbage. The spatial distribution of R. venosa within the estuary was coupled with the spatial distribution of Mactra isabelleana, a typical subtidal bivalve of mixohaline waters. The implications for the food webs of the estuary, including possible predators, are discussed. The presence of R. venosa in muddy sediments together with the finding of egg-capsules over the specimens, and the low salinity values at which it is found in the Rio de la Plata estuary, confirmed the high plasticity of R. venosa and the potential capability of successfully invading novel environments. Sun, 01 Jan 2006 00:00:00 GMT http://hdl.handle.net/1834/1572 2006-01-01T00:00:00Z http://hdl.handle.net/1834/1570 Title: Crecimiento y rendimiento en carne del Lenguado Paralichthys orbignyanus (Valenciennes, 1839) cultivado en Argentina Authors: Müller, M.I.; Radonic, M.; López, A.V.; Bambill, G.A. Abstract: The results of the final on-growing (500 g to 1 kg)of flounder Paralichthys orbignyanus under closed recirculated water systems and controlled conditions are presented. 22.5 percent of fish reached 1 kg alter 2.1 months of starting the on-growing trial. Sex ratio was 20.6 percent females and 79.4 percent males. Average length for females and males was 38.53 ± 4.58 cm TL and 32.52 ± 5.25 cm TL, respectively. Average body weight for females and males was 710.58 ± 262.95 g and 427.59 ± 203.01 g, respectively. Statistically significant differences were found for average length for sex (p0.01)and for average body weight for sex (0.01 0.05). Flesh yield was 43.1percent fillets without skin and 57percent fillets with skin. Flesh of cultivated flounder had a higher proportion of lipids and humidity than flesh of wild flounder. The present study shows the aquaculture potential of flounder Paralichthys orbignyanus and the higher growth of females suggests the convenience of monosex culture Sun, 01 Jan 2006 00:00:00 GMT http://hdl.handle.net/1834/1570 2006-01-01T00:00:00Z