水槽内に出現したイカリヨツボシクラゲ(刺胞動物門, ヒドロ虫綱, 花クラゲ目)の166日間の成長と老衰そして新たな分布の可能性

Abstract

A young medusa of Pandeopsis ikarii with 2 marginal tentacles and 2 marginal warts was collected from a jellyfish breeding tank. It was kept for 166 days until degeneration at room temperature 22.1-26.4°C, fed with Artemia nauplii and fish meat. Tentacles increased to 8 on the 28th day and not increased thereafter. A total of 24 marginal swellings were observed on the 96th day. The bell diameter had reached 11 mm on the 102nd day, thence not increased. On the 30th day at least three light black spots existed on the manubrium. Black spots increased in number and became dark with the growth of the medusa, lastly on the 116th day about 30 clear black spots were found on the manubrium. The small ovaries were formed on and after the 122nd day but they did not mature. On the 33rd day a cirrus appeared on the tentacle bulb just on the position of ocellus, and on the 35th day the second cirrus was formed, then they disappeared at least on the 50th day. Presence of cirri suggests the kin relationship between Pandeidae and Leptomedusae. This species will be found from Mie Prefecture in the future, judging from breeding circumstances.