Changes in biomass and elemental composition during early ontogeny of the Antarctic isopod crustacean Ceratoserolis trilobitoides

Changes in biomass and elemental composition (dry mass, DM; carbon, C; hydrogen, H; nitrogen, N) were studied throughout the early ontogeny in the serolid isopod Ceratoserolis trilobitoides from a population off the South Shetland Islands (62°24.35?S, 61°23.77?W). Specimens of C. trilobitoides were sampled using an Agassiz trawl during the expedition ANT XXIII-8 of RV Polarstern in January 2007. Classification of embryos into six developmental stages followed previous studies. No clear size-dependant fecundity relationship was found in ovigerous C. trilobitoides. Egg volume increased by about 160 and 400% from stage I to IV and stage IV to VI, respectively. DM, C, N, and H continuously decreased throughout the early ontogeny from stage I to VI, but DM showed significant increase on reaching the late-V stage and premanca stages. The C:N ratio remained relatively stable throughout stages I to V, followed by a significant drop from about 6.17 to 5.5 in subsequent stages, indicating depletion of lipid resources of maternal origin. The results coincide with previous studies and indicate a shift from a lipid-based metabolism throughout early embryo stages to a protein-based metabolism in the late-V and premanca stage, which requires external energy supply. Given the steep increase in DM in the final phase of embryo development (late-V stage to premanca) and the need for external food supply to exert growth, the possibility of external food supply or cannibalism in early offspring of C. trilobitoides is discussed

Reproduction patterns of four Antarctic octocorals in the Weddell Sea: an inter-specific, shape, and latitudinal comparison

13 pages, 6 figures, 5 tablesThe reproductive patterns of four Antarctic gorgonian species have been investigated. Two of them, Dasystenella acanthina and Thouarella sp., present the bottle-brush-shape type; the other two, Fannyella rossii and Fannyella spinosa, are fan-shaped. Two different reproductive patterns have been observed in D. acanthina and Thouarella sp., which point to two size classes in the frequency distribution of oocytes. This feature indicates a reproduction cycle with overlapping generations, being each of them of more than one year, probably with seasonal spawning. F. rossii and F. spinosa show only one size class of oocytes, which could point towards an annual reproductive cycle. The presence of larvae in the gastrovascular cavities in both Fanyella species and Thoaurella sp. is a sign of a possible larvae release during austral summer. The number of oocytes per polyp ranges from 1.1 ± 0.10 SE to 1.5 ± 0.06 SE, and the size ranges from 50 to 1200 μm. The number of spermatic cysts ranges from 2.6 ± 0.19 SE to 5.0 ± 0.21SE, and their sizes range from 50 to 800 μm. These values are comparable to the reproductive trends and features found in gorgonians from other latitudes, which correspond in some cases with similar morphotypes. These coincident strategies could be related to morphological similarities rather than with latitude or water temperature. The results of this study indicate that octocoral morphology may play a crucial role in determining the reproductive output of these organismsFinancial support for this study was provided by a European Comission fellowship within the programme “Training and Mobility of Researchers” (TMR-CT97-2813), by CICYT (Spanisch Antarctic Research Programme) grants ANT98-1739-E and ANT099-1608-E, and by the programme “Acciones integradas hispano-alemanas” (314-Al-e-dr/ia. “Ministerio de Educación y Ciencia” and DAAD (Deutscher Akademischer Austauschdienst)Peer reviewe