The contents of three essential fatty acids, arachidonic acid (AA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), from wild Penaeus monodon broodstock were evaluated in comparison with natural diet fed P. monodon. Spermatophores of wild male broodstock contained higher levels of AA than those of arti¢cial diet fed males. Polychaetes had higher proportion of AA to EPA and DHA at 5.8:5.5:1 in mud polychaetes followed by 12:7:1 in sand polychaetes, while DHAwas a preferential n-3 highly unsaturated fatty acid (HUFA) in squids and ¢sh. The experimental feed was constructed to simulate the HUFA pro¢le of polychaetes (AA:EPA:DHA as 5:1:1) and then fed to farmed male black tiger prawn broodstock for 1 month. The results exhibited comparable reproductive characteristics to wild male suggesting the possibility of replacing wild males with pondreared males. Rearing farmed males in a test unit for a month did not reduce the quality of prawn sperm. Reproductive performance indices (sperm sac weight, total number of sperm, percentage of live sperm, percentage of abnormal sperm) from the males of all treatments were not statistically di¡erent except in males fed with pellets. Control (live feeds) and combined diet provided better reproductive performance in pond-reared males. Analysis of AA, EPA and DHA in reproductive tissues, hepatopancreas and muscle of treated animals in each treatment revealed an accumulation of dietary HUFA into reproductive tissues. No evidence of transfer of HUFA from hepatopancreas or muscle to spermatophore was found.

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Prostaglandins are involved in the reproductive processes in a variety of animals, including crustaceans. It was found that polychaetes, the best maturation diet for shrimp broodstock, possessed the greatest variation of prostaglandin E 2 (PGE 2 ) when compared with other live feeds. The level of PGE 2 varied according to sizes, feed intake, sources and type of polychaete. The matured and also larger sand polychaete Perinereis sp. contained higher PGE 2 levels than younger and smaller sand polychaetes (18.16 ± 5.82 ng PGE 2 mg -1 protein for polychaetes at an average length of 10 cm up to 160.8 ± 37.09 ng PGE 2 mg -1 protein for polychaetes at an average length of 17 cm). The PGE 2 levels in ovaries and haemolymph of female shrimp fluctuated with the developmental stage of the ovaries. The highest concentration of PGE 2 in haemolymph was at stage 3 of ovarian development, whereas the highest concentration of PGE 2 in shrimp ovaries was at stage 4. In vitro incubation of Penaeus monodon pre-vitellogenic oocytes with polychaete extract and synthetic PGE 2 demonstrated that both PGE 2 s enhanced oocyte development, especially during late development and ovulation. The putative role of PGE 2 from polychaetes or the presence of PGE 2 in polychaetes may be a factor in their role as a dietary constituent required for shrimp oocyte development.

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