International audienceKnowledge on the energy distribution during the reproductive cycle of the giant lion-paw scallop, Nodipecten subnodosus is limited, but necessary for aquaculture purposes. In a previous work, we found that natural food availability can sustain the full cost of gametogenesis in optimal environmental conditions. The present study analyses the lipid and sterol classes' composition of several tissues during gametogenesis. In female gonads, the quantity of triacylglycerol (TG) increased parallel to gametogenesis from December (spawned gonads, 0.7 mg g(-1) or 7% of total lipids) to June (ripe gonads, 52 mg g(-1) or 66% of total lipids). In male gonads sampled in June, the concentration of TG (0.7 mg g(-1) or 3.5% of total lipids) and esterified sterols was significantly lower than in female gonads. Total phospholipids (PL) increased two-fold in female gonads of scallops sampled in June compared to the other months, which could be a result of oocyte production and growth, but no differences were found in the concentration of PL or in free sterol composition between male and female gonads. TG concentration in the digestive gland was similar in December and February (37-3 8 mg g- 1 or 68% of total lipids), but increased eight-fold by April and remained high in June (252-277 mg g(-1) or 90% of total lipids). Together with the increase in esterified sterols, these data suggest an increase in food availability during these months. A lack of decrease of TG levels in digestive gland during gonad development is in accordance to sufficient food availability in this location to satisfy the energetic demands of gametogenesis. Cholesterol was the principal sterol found in all tissues; its concentration, as well as the concentration of several phytosterols, remained constant throughout the maturation process, except in digestive gland where they increased from December to June, further supporting an increased availability of food. However, the presence of several phytosterols in substantial concentrations, mainly brassicasterol and 24-methylenecholesterol in gonad and somatic tissues, further supports a specific physiological role of these sterols in pectinids. (c) 2007 Elsevier B.V. All rights reserved

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Litopenaeus vannamei (Boone) grown in ponds are exposed to salinities of less than 5 g L−1 during inland shrimp culture or to more than 40 g L−1 from evaporation and reduced water exchange in dry, hot climates. However, dietary requirements for shrimp grown in low or high salinities are not well defined, particularly for fatty acids. Feeding shrimp postlarvae with highly unsaturated fatty acids (HUFA) enhances tolerance to acute exposure to low salinity, as a result of better nutritional status, or/and specific effects of HUFA on membrane function and osmoregulation mechanisms. This study analysed the effect of HUFA supplementation (3% vs. 34%) on L. vannamei juveniles reared for 21 days at low (5 g L−1), medium (30 g L−1) and high salinities (50 g L−1). Juveniles grown at 5 g L−1 had lower survival compared with controls (30 g L−1) or shrimp grown at 50 g L−1, but no significant effect on survival was observed as a result of HUFA enrichment. In contrast, growth was significantly lower for shrimp grown at 50 g L−1, but this effect was compensated by the HUFA‐enriched diet. Osmotic pressure in haemolymph was affected by salinity, but not by HUFA enrichment. Shrimp fed HUFA‐enriched diets had significantly higher levels of eicosapentaenoic acid and docosahexaenoic acid in hepatopancreas and gills. These results demonstrate that growth at high salinities is enhanced with diets containing high HUFA levels, but that HUFA‐enriched diets have no effect on shrimp reared at low salinities.

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