Sperm Quality in Relation to Age and Weight of White Shirimp Litopenaeus Vannamei

Optimal sperm quality is an important feature for management of shrimp broodstock. The understanding of the sperm quality in relation to age and weight of shrimp is useful to select male broodstock. To evaluate the effect of age and weight on sperm quality, Litopenaeus vannamei males from the same cohort at ages of 6, 8, 10, and 12 months were examined, using body weight as a covariable in ANCOVA. Additionally, males of the same cohort at an age of 12 months, but from different culture conditions, were compared. Spermatophore weight, sperm count, and percentage of normal sperm were positively correlated to body weight. Sperm count was positively correlated to spermatophore weight and percentage of normal sperm. Males at an age of 12 months had superior sperm quality than younger males, based on observations of larger spermatophore weight, higher sperm count, and higher percentage of normal sperm. By eliminating the influence of body weight with the use of ANCOVA, the same effect was still observed, indicating that the effect of age of males on sperm quality was independent of body weight. However, when large differences in growth were forced by changing culture conditions, sperm quality differences were observed and could be explained by body weight. In conclusion, using 12-month-old males would lead to improved shrimp seed production, since they are mature males with high sperm quality. In addition, for improved productivity, it is important to consider the culture conditions under which domesticated male broodstock will be obtained

Lipid composition of the giant lion's-paw scallop (Nodipecten subnodosus) in relation to gametogenesis: I. Fatty acids

cited By 37International audienceSeasonal variations in fatty acid composition in several tissues of a 1-year-old population of giant lion's-paw scallop Nodipecten subnodosus were analyzed during gonad development. Samples were taken bimonthly from December 1999 to June 2000, a period in which gonad development was occurring. Fatty acid accumulation in neutral and polar lipids of the female gonad was concomitant to the gonad development and presented a maximum in June. Among essential fatty acids, a specific accumulation was observed only for 20:5n - 3 in the female gonad, as suggested by an increase in its proportion in the neutral and the polar fractions. However, no specific accumulation was observed for 22:6n - 3, as its proportion remained relatively constant in both fractions. We suggest that a specific increase of 22:6n - 3 is not necessary during gametogenesis because its proportion was high enough for reproductive purposes (20-30%). Although some data suggest a partial mobilization of polyunsaturated fatty acids from the muscle and digestive gland to the female gonad during gonad development, the main supply came directly from the diet. The maximum increase in total and specific fatty acids in the digestive gland occurred in April and was maintained in June. These changes reflect either a higher lipid availability of the food, or the beginning of storage process in the digestive gland. However, in the female gonad, the maximum increase was observed in June, whereas gonad development and spawning were observed from April. It is suggested that different patterns of lipid accumulation in the first (April) and second (June) maturation processes could be related to the reproductive cycle of this species, which exhibits an initial facultative maturation during spring and the main reproductive activity during summer. © 2005 Elsevier B.V. All rights reserved

Lipid composition of the pacific lion-paw scallop, Nodipecten subnodosus, in relation to gametogenesis

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

Effect of diets containing different levels of highly unsaturated fatty acids on physiological and immune responses in Pacific whiteleg shrimp <i>Litopenaeus vannamei</i> (Boone) exposed to handling stress

Juveniles fed a diet containing a low or a high level of highly unsaturated fatty acids (HUFA) for 38 days were exposed to handling stress. In a first experiment, stress was applied daily for 30 days, after which the physiological and immunological variables were measured, whereas in a second experiment, stress was applied once and samples were obtained 1 and 24 h after the stressor event. Shrimp that were stressed for 30 days showed significantly lower survival, final weight and feed consumption compared with unstressed shrimp. The concentration of the high-density lipoprotein beta-glucan-binding protein was significantly higher in shrimp fed the high-HUFA diet. The glucose concentration in the haemolymph was significantly higher in long-term stressed shrimp compared to controls. The lactate level in the haemolymph was significantly lower in shrimp fed the high-HUFA diet. Lactate and glucose in the haemolymph increased in the 1-h stressed shrimp, but returned to normal levels in 24-h stressed shrimp. A negative effect of repeated-handling stress applied for 30 days was mainly observed on biological performance, whereas the single-stressor event had a more pronounced effect on shrimp physiological and immune responses measured 1 and 24 h after the stressor. A beneficial role of enrichment with HUFA on tolerance to handling stress was observed on immune response capacity