The effect of dietary EPA and DHA on the molting rate of larval swimming crab Portunus trituberculatus.
This experiment was conducted to investigate the effectiveness of two n-3 highly unsaturated fatty acids, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), for larval swimming crab P. trituberculatus. Two experiments were carried out in 1-litre beakers in duplicate, each holding 30 larvae. Starting with the larval stage zoea 3, and though the megalopa stage, they were fed Artemia containing different amounts of EPA and/or DHA prepared using emulsified oils (EPA ethyl ester, DHA ethyl ester, and DHA38G). During the feeding experiments, the molting rate and the inter-molt period in days to reach each stage were measured. It was found that EPA and DHA had different roles in larval development. EPA was effective in maintaining the survival rates for larvae, while DHA accelerated the developmental period and improved the growth of carapace. The highest molting rate and largest carapace width at the first crab were observed when the larvae were fed Artemia enriched with DHA38G from the zoea 3 stage. Larvae fed unenriched Artemia had low molting rates and the smallest carapace width. These results suggest that it is important to feed the swimming crab with Artemia containing both EPA and DHA from the zoea 3 stage to avert the high rate of cannibalism among them during mass seed production.