Induced out-of-season spawning of the mud crab, Scylla paramamosain (Estampador) and effects of temperature on embryo development

摘要

Treated with combined bilateral eyestalk ablation and maintenance of water temperature at 22.5pl1.5 pC, mud crab Scylla paramamosain females with mature ovaries were induced to produce eggs outside the natural spawning season in subtropical southern China. Newly extruded eggs from a crab were incubated in vitro at 10, 15, 20, 25, 27, 30, 35 pC, respectively, and the embryonic development was closely monitored. Abnormal cell division was observed at temperatures 10 and 35 pC. At 15 pC, development remained at the gastrula stage by day 32 post-spawn, at which time the experiment was terminated. Hatching of in vitro incubated eggs occurred between 20 and 30 pC. An increase in incubation temperature from 20 to 25 pC reduced the incubation duration by 14 days, 2.6 times of that measured for a similar 5 pC increase from 25 to 30 pC. Embryonic development of S. paramamosain was divided into stage 0-10, and the duration of each stage was recorded for each incubation temperature. The information obtained allows accurate prediction of hatching time of female crabs incubated under variable temperatures. Larvae hatched from in vitro incubated eggs were reared to reach first juvenile crab stage and their dry weights were similar to those of larvae hatched naturally.