FEEDING AND STARVATION TOLERANCE OF THE YOLK-SAC LARVAE OF GOBIOCYPRIS RARUS

Eleven batches of yolk-sac larvae of Gobiocypris rarus were reared at 25±1℃ to study the feeding ability and starvation tolerance.The time to initial feeding and to the point-of-no-return (PNR, when 50% larvae are no longer strong enough to feed) was determined, and characters of development both on fed and unfed larvae were observed.The larvae began to feed on 1.5-2d after hatching, when the yolk volume was less than 0.03mm3 (0.1 when hatching).The initial feeding rate usually reached its peak in 1-1.5d when the yolk became exhausted.The highest feeding rate was 100%, and the time keeping the rate above 80% was 4 to 5 days.Starvation has disadvantageous effect on growth, development and survival.Not only the starved larvae occurred in negative growth, but also showed a series of characters, including decrease in size of various organs, the pectoral angle etc.The PNR was 8 to 10 days after hatching, with a mode of 9.On 1-2d before PNR, the survival rate of starved larvae became lower than 50 %, while all unfed larvae died within 2 days after PNR.