흰멍게(Styela plicata)의 번식주기 및 자연채묘 유생의 성장

Abstract

Abstract

In order to investigate the reproduction, settlement of larvae onto the substratum, and the growth process of the sea squirt Styela plicata, aqua cultural studies were conducted on the animal which was cultured along the coast of Jindong, Changwon-si, Kyongnam between 2005 and 2006. The reproductive cycle can be classified into four successive phases; growing, mature, spawning and the resting stages. The spawning stage extendeds from May to October with the early spawning portion covering in May and June and the late spawning portion covering in August and September. A sea squirt Styela plicata’s embryo was a segregated demersal egg, which took two hours to develop into 2-cell stage, three hours into the 8-cell stage, and four hours into the 16-cell stage. The morula stage occurred after six hours. Then tadpole larva appeared in 13 hours. The tail was then absorbed as it metamorphosis into a matured juvenile and had settled into a position in the colony within approximately 24 hours. Occurrence of the tadpole larva stage extendeds from May to October, with the early stage in May and June and late stage in August and September. Most of settled juveniles of the sea squirt Styela plicata seemed to be found attached to the upper surface of the artificial substratum dispersed at about 3 meters below the water surface. After fertilization, it took 4 to 5 months to grow more than 50 mm or to a suitable size for harvest. Suitable water temperature for growth ranged at 20℃ to 25℃. The sea squirt Styela plicata also grew more rapidly in an environment of rising water temperature than in a descending water temperature environment.

Key words: Sea squirt, Styela plicata, Reproductive cycle, Egg development, Naturally collected larva, Growth