The content of ascorbic acid and tocopherol in the tissues and eggs of wild <i>Macrobrachium rosenbergii</i> during maturation

Variations in the concentrations of ascorbic acid (AA) and tocopherols in association with the gonadal development of the freshwater prawn Macrobrachium rosenbergii were investigated in females captured in the Mae Klong River, Thailand. Mean ovarian AA levels ranged from 210 to 540 µg/g dry weight (dw) and were at least 11-fold higher than midgut gland (MG) levels. Variations in ovarian AA levels are believed to be related to the biosynthesis of steroid hormones, the formation of collagen, and the deposition of egg yolk compounds. alpha-Tocopherol (alpha-T) was the predominant form of vitamin E in prawn tissues and eggs. The level of alpha-T in the MG was constant, whereas in the ovaries, it ranged from 143 to 425 µg/g dw. The incorporation of a-T into the ovary was highly correlated (r² = 0.87) to ovarian lipid levels, which probably reflects the role of this vitamin as a major antioxidant agent. The present results provide further evidence of the essentiality of these vitamins in crustacean reproduction

Performance of <i>Macrobrachium rosenbergii</i> broodstock fed diets with different fatty acid composition

The effect of linoleic acid (18:2n-6) and n-3 highly unsaturated fatty acids (HUFA) on the reproductive performance and offspring quality of the freshwater prawn Macrobrachium rosenbergii was evaluated in a 180-day trial. Three isonitrogenous and isolipidic diets containing different levels of fatty acids, high 18:2n-6 and n-3 HUFA concentrations, high 18:2n-6 and low n-3 HUFA, and low 18:2n-6 and n-3 HUFA, were fed ad libitum to three groups of six females. Fecundity was improved by the addition of higher amounts of 18:2n-6 (from 3 to 13 mg g-1 DW). As a consequence of higher fecundity, smaller eggs were obtained most likely because the number of oocytes competing for a limited amount of yolk was higher. The higher gonado-somatic index of females fed diets with high levels of 18:2n-6 and n-3 HUFA levels further supports this hypothesis. The fatty acid composition of the eggs reflected to some extent the composition of the diets. Eggs of females fed high levels of 18:2n-6 and n-3 HUFA had the highest n-3 HUFA content and had increased hatchability. Eight-day-old larvae from females fed high levels of 18:2n-6 and n-3 HUFA tended to present a better stress tolerance when exposed to 100 mg l-1 total ammonia for 24 h. No other differences were detected among larval characteristics from the different offspring groups. Results demonstrate that feeding M. rosenbergii broodstock with high levels of 18:2n-6 and n-3 HUFA (13 and 15 mg g-1 DW, respectively) improved fecundity, egg hatchability, and the overall quality of the larvae

Maturation performance, offspring quality and lipid composition of <i>Macrobrachium rosenbergii</i> females fed increasing levels of dietary phospholipids

The effects of increasing levels of dietary phospholipids (PL) on the reproductive performance, egg and larval quality, and lipid composition of females of the freshwater prawn Macrobrachium rosenbergii were investigated. Three isolipidic diets containing similar amounts of highly unsaturated fatty acids but varying levels of PL (0.8, 2.4 and 4.6%) were fed during 180 days to three groups of eight females originating from Thai ponds. No significant differences were observed for fecundity, egg size and hatchability, starved larvae size, and size, survival and tolerance to stress of 8 day-old larvae. Similarly, no major differences in the lipid composition of the midgut gland, ovaries and muscle tissue of females could be detected. Results indicate the lack of need of dietary supplementation of PL for M. rosenbergii broodstock, as previously reported for earlier life stages. It is suggested that the basal level of 0.8% dietary PL was sufficient to meet the dietary demands of the prawn broodstock. The PL requirements of M. rosenbergii broodstock, if any, may be satisfied in commercial feeds through the inclusion of ingredients containing some phospholipids endogenously

Variations in lipid classes and fatty acid content in tissues of wild <i>Macrobrachium rosenbergii</i> (de Man) females during maturation

This study describes the variations in total lipid, lipid classes and fatty acids in the midgut gland (MG), ovary, and muscle tissue of wild-caught Macrobrachium rosenbergii to elucidate the importance of these components during sexual maturation. Mature females were captured in the Mae Klong River, Thailand, from July to September 1998, and divided into five groups according to their ovarian development. Total lipid levels in the ovary increased with maturation, but no concomitant decrease in MG lipids was observed. Thus, the lipid requirements of the developing ovary are thought to be more dependent on the immediate ingestion of dietary lipid than on MG reserves. Higher proportions of neutral lipids (NL), mainly triacylglycerols (TG), were observed in both MG and ovary, whereas polar lipids (PL) predominated in muscle. In the ovary, total NL increased significantly along with maturation mainly due to an increase of TG and sterols.Phosphatidylcholine (PC) and phosphatidylethanolamine (PE) formed the bulk of ovarian PL and also increased significantly as maturation progressed. Major fatty acids in both MG and ovary were 14:0, 16:0, 18:0, 18:1n-9, 18:2n-6, 18:3n-3, 20:4n-6, 20:5n-3 and 22:6n-3. Significant increases in the levels of saturated and mono-unsaturated fatty acids were observed in both MG and ovary. The levels of n-3 highly unsaturated fatty acids (HUFA), particularly 20:5n-3, decreased in the MG as ovarian development proceeded. In contrast, an increase in the ovarian contents of n-3 HUFA was detected

Induced thermotolerance and stress resistance in larvae of the freshwater prawn, <i>Macrobrachium rosenbergii</i> (de Man, 1879)

Optimal conditions for heat shock (HS) were used to demonstrate induced thermotolerance (ITT) in larvae of the prawn, Macrobrachium rosenbergii. Larvae from three different broodstock nutritional regimes exhibited comparable degrees of ITT, which remained high for about 4 days. Survival and growth of larvae given the standard HS treatment (37 °C for 30 min) were not statistically different from those of controls, so the cost of mounting a heat shock response was not sufficient to reduce those parameters. However, the percentage of heat-shocked larvae undergoing metamorphosis appeared to be slightly lower than that of controls. Previously heat-shocked larvae withstood hypersalinity exposures much better than control larvae, but showed the same survival level when both were challenged with ammonia toxicity. We suggest that the use of induced thermotolerance might provide a means to improve the performance of larvae during transport and/or initial inoculation into grow-out ponds. The present paper provides the basis upon which that suggestion might be examined

Experimental culture of the river prawn Macrobrachium americanum larvae (Bate, 1868), with emphasis on feeding and stocking density effect on survival [Cultivo experimental de larvas de langostino Macrobrachium americanum (bate, 1868), con énfasis en alimentación y efecto de la densidad sobre la supervivencia]

The cauque river prawn Macrobrachium americanum occurs along the Pacific coast of America. This prawn can grow to a large size, making it an interesting option for aquaculture production. Currently, supplies of juveniles are limited because hatchery and laboratory-reared larvae are difficult to raise. This study assesses larval survival for different combinations of stocking density and feeding from larvae cultivated in green water. From these combinations, larvae fed with Artemia nauplii and maintained at a density of 50 larvae L-1 had the highest survival