Screening of Fatty Acid Composition of the 13 Microalgae and Their Application in Artificial Breeding of Mitten Crab

Fatty acid composition of 13 species of marine and freshwater microalgae and 5 clones of Phaeodactylum tricornutum were studied from 1996 to 1999. The microalgae were cultured under optimal conditions respectively and harvested during later log phase. The results suggest that there is high C20∶5(EPA) content in the cells of P. tricornutum, Skeletonema costatum, Nitzschia closterium, Chaetoceros muelleri and Pavlova viridis, their EPA percentage in total fatty acids being 19.13%～28.00%, 24.62%, 27.80%, 21.45% and 26.65%, respectively. All the determined species are poor in C22:6(DHA) except P. viridis (10.35% of total fatty acid), Isochrysis galbana (7.58%)and Isochrysis sp. (8.89%). The experiments of feeding the larvae (Z 1) of mitten crab with different microalgae were carried out, and the results show that the metamorphosis of larvae fed with P. tricornutum or I. galbana is distinctly higher than those fed on other algae (Chlorella sp. and Spirulina platensis) or hen's eggs which are poor in EPA or DHA.