A REVIEW OF
STUDIES ON THE EFFECT OF DIETARY N-3 HIGHLY UNSATURATED FATTY ACIDS ON
LARVAL SWIMMING CRAB PORTUNUS TRITUBERCULATUS and MUD CRAB SCYLLA
TRANSQUEBARICA
T. Takeuchi-2001
Proc. JSPS Int. Symp. Fisheries Sci. Tropical Area, in press
Abstract:
This paper reviews the effect of n-3 highly unsaturated fatty acids (n-3 HUFA; both eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA)) on swimming crab and mud crab larvae from a nutritional perspective.
Larvae of the swimming crab Portunus trituberculatus, fed on rotifers cultured with the freshwater chlorella Chlorella vulgaris or enriched with corn oil, seldom reached the first crab stage, indicating that perhaps both linolenic and linoleic acids in the rotifer were not essential fatty acids for the swimming crab. In contrast, larval survival rate, growth and development velocity improved according to the amount of n-3 HUFA contained in rotifers. On the basis of the feed performance and fatty acid compositions of rotifers, the suitable levels of n-3 HUFA for larval swimming crabs were between 0.9-0.7g/100g on a dry eight basis. It also suggested that swimming crab larvae should be fed Artemia containing n-3 HUFA from the zoea 3 stage in order to get a high survival rate at the first crab stage.
It is also effective to give Artemia containing n-3 HUFA to larvae of the mud crab Scylla transquebarica from the zoea 3 stage. Mud crab larvae fed unenriched Artemia containing 1.3% EPA alone showed the best survival rate and highest molting rate. A high survival rate and wide carapace at the first crab stage were also observed in mud crab fed DHA-enriched Artemia containing trace DHA (0.46% DHA, plus 1.6% EPA). These results suggest that suitable levels of EPA and DHA in Artemia for mud crab were about 1.3-2.2% and 0.46%, respectively.
In consequence, swimming crab and mud crab larvae definitely need EPA for survival, while DHA was required for carapace growth. It is also important to give Artemia enriched with n-3 HIFA from the zoea 3 stage in order to improve survival rates.
(Department of Aquatic Biosciences, Tokyo University of Fisheries, Konan, Minato, Tokyo 108-8477, Japan,
e-mail: take@tokyo-u-fish.ac.jp)