The aim of the present work was to obtain the lipid utilization of Octopus vulgaris supplying formulated semi-moist diets with different contents in cod oil (reduced from water content): 0 g kg À1 (A0, 138 g kg À1 lipids DW; N = 4), 100 g kg À1 (A100, 286 g kg À1 lipids DW; N = 6) and 200 g kg À1 (A200, 388 g kg À1 lipids DW; N = 6). The rest of the ingredients were constant in the three diets: 200 g kg À1 gelatin, 100 g kg À1 egg yolk powder, 150 g kg À1 freeze-dried Todarodes sagittatus and 50 g kg À1 freeze-dried Sardinella aurita). Survival was 100% with the three diets. The highest absolute feeding (15.8 AE 1.2 g day À1 ), growth (9.6 AE 1.4 g day À1 ; 0.91% BW day À1 ) and feed efficiency rates (60.3%) were obtained with diet A0. This diet also showed greater retention of lipid and protein than A100 and A200. Protein digestibility was above 95% in all of the diets. Only diet A0 led to a high lipid digestibility coefficient (81.25%), which fell drastically to 12.3% in A200. It was notable the high polar lipid digestibility rates (83-89%) respect to neutral lipids (2-87%) in all diets. The best results were obtained with lipid feeding rates of around 1 g day À1 and a suitable lipid content on 130-140 g kg À1 DW in formulated diets for O. vulgaris.

No abstract

Habitat degradation can affect trophic ecology by differentially affecting specialist and generalist species, and the number and type of interspecific relationships. However, the effects of habitat degradation on the trophic ecology of coral reefs have received limited attention. We compared the trophic structure and food chain length between two shallow Caribbean coral reefs similar in size and close to each other: one dominated by live coral and the other by macroalgae (i.e., degraded). We subjected samples of basal carbon sources (particulate organic matter and algae) and the same 48 species of consumers (invertebrates and fishes) from both reefs to stable isotope analyses, and determined the trophic position of consumers and relative importance of various carbon sources for herbivores, omnivores, and carnivores. We found that both reefs had similar food chain length and trophic structure, but different trophic pathways. On the coral-dominated reef, turf algae and epiphytes were the most important carbon source for all consumer categories, whereas on the degraded reef, particulate organic matter was a major carbon source for carnivores. Our results suggest that the trophic structure of the communities associated with these reefs is robust enough to adjust to conditions of degradation.