人工採苗マコガレイの体色異常個体の出現に及ぼす飼育密度および水槽の色の影響

抄録

The effect of population density and tank color on the appearance of abnormal coloration in juvenile mud dab, Limanda yokohamae, was studied by rearing experiment. Two days old larvae were stocked by series of tanks (transparent and black), each with six tanks. These larvae were reared with same fbods (rotifer, Brachionus plicatilis, Tigriopus japonicus and minced meat) . High population density and tank color slightly decreased the frequency occurrence of albinic juveniles. Then changes of coloration in tank reared juveniles were examined. Continuous irradiation with sun light decreased slowly their albinic portions on ocular side and increased their. ambicolored portions on blind side. As one of morphological abnormalities associated with abnormal coloration, the abnormality of eye migration was examined. On the juveniles with almost total albinism (almost total ambicoloration), the incompete and reversed eye migration were found in 3.67% and 12.44% of specimens examined (99.76% and 30.62%) respectively, which were extremely higher rate than in the other color type juveniles.