동남참게 초기유생에 대한 생리 생태학적 연구

Physiological and ecological studies on the early larval stages of a fresh water crab, eriocheir japonicus

The present experiment was designed to obtain the adequate condition of temperature, daylength and salinity on the gonadal maturation of adult female, spawning and hatching of egg, and growth of larvae of the freshwater crab Eriocheir japonicus. Gonadal maturation was influenced by water temperature, but not daylength. GSI of female crabs more increased in experimental regime of 18℃ than that of 10℃ without regard to photoperiod conditions(12L/12D and 15L/9D). However, in both photoperiod conditions of 26℃ regime, GSIs were not changed, and vitellogenic oocytes were not observed. Spawning was considerably influenced by water temperature and salinity without regard to daylength. Vitellogenic female crabs did not spawn at 10℃ in any conditions of salinity. However, at 18℃ and 26℃, over a half of rearing female crabs spawned in condition of 30% sea water(salinity 9.6‰) and 60% sea water(salinity 19.2‰), while no spawned females appeared in freshwater condition(salinity 0.0‰). In 20% sea water(salinity 6.4‰) and less conditions, ovigerous female crabs removed eggs from the abdormal egg-chamber of one s own self before hatching out. However, all ovigerous female crabs hatched out in 40% sea water(salinity 12.8‰) and more conditions. Hatching rates were 33.3% and 83.3% in 40% sea water condition and in 60% and 80% sea water conditions, respectively. In experiment of effects on temperature on hatch out of eggs, hatching rates of eggs were 66.7% and 83.3% at 18℃ and 26℃, respectively. whereas, at 10℃ and 32℃ conditions, ovigerous females died or removed eggs before hatching out. In investigation of days required to hatch out from brooding time according to the water temperature, required days to hatch out were 28.0±1.7 days in 18℃ condition and 14.0±0.3 days in 26℃. In 20% sea water and less conditions, zoea larva died before metamorphosing to larvae of megalopha stage. However, in 40% sea water and more conditions, zoea larva metamorphosed to megalopha stage. Rates of metamorphosed zoea larva to megalopha stage were 32%, 44% and 48% in conditions of 40%, 60% and 80% sea water, respectively. Under rearing condition of 80% sea water, all of the first stage of zoea larva reared at 10℃ did not metamorphose to the second zoea stage and than died within 24 days. At 15℃, 16% of zoea larva metamorphosed to the fifth zoea stage. However, larva metamorphsing to meglaopha stage were observed from 20 and 14 days rearing at 20℃ and 26℃, respectively.