Purification of vitellin from the ovary of Chinese mitten-handed crab (Eriocheir sinensis) and development of an antivitellin ELISA.

Vitellin was purified from ovaries of mature female Chinese mitten-handed crab (Eriocheir sinensis) using gel filtration chromatography. Analysis by native PAGE showed the vitellin had a native molecular mass of 520 kDa, while denaturing SDS-PAGE revealed two subunits of 97 and 74 kDa. Purified vitellin was used to raise polyclonal antisera, with which an enzyme-linked immunosorbent assay (ELISA) was developed. The ELISA was sensitive and could effectively detect vitellin in the range of 7.8-500 ng. Furthermore, vitellin levels in various developmental stages of oogenesis were measured with the ELISA assay. The results indicated that levels of vitellin increased significantly from 0.22 mg/ovary at Stage II to 360.31 mg/ovary at Stage IV.

Reproduction response of Chinese mitten-handed crab (Eriocheir sinensis) fed different sources of dietary lipid.

The effect of feeding three semi-purified diets containing different lipid sources (anchovy oil, soybean oil and pork lard) on fecundity, hatchability and egg fatty acid composition of Chinese mitten-handed crab (Eriocheir sinensis) broodstock was compared with a fresh clam diet in a 6-month feeding trial. Broodstock crabs fed the diet containing pork lard showed poor fecundity and low hatchability. Crabs fed the diet containing soybean oil showed improved fecundity; however, no significant improvement in hatchability was observed. Broodstock fed the diet containing anchovy oil showed the highest fecundity and egg hatchability. Eggs from broodstock fed anchovy oil as sole dietary lipid had a higher n-3 polyunsaturated fatty acid (PUFA) content (33.3%) compared with those of crabs fed diets with soybean oil (20.1%) and pork lard (16.3%) as lipid sources. The results indicate a close correlation between: (1) the 20:5n-3 content of the egg lipid and fecundity; (2) the 22:6n-3 content and hatchability; and (3) fecundity, hatchability and n-3/n-6 fatty acid ratio. The results also suggest that each of these n-3 HUFAs may play different and specific roles in crab reproduction and that either must be adequate in the broodstock diet.