Abstract
During the years from 1977 to 1981 four specimens of Bougainvillia bitentaculata UCHIDA, 1925 were collected at Oshoro, Hokkaido, northern Japan. An immature specimen, 0.75 mm in umbrellar width and 0.63 mm in umbrellar height and with three marginal tentacles and four unbranched oral tentacles, was reared in laboratory for 83 days, fed with Artemia-nauplii, and the metamorphosis and the nematocyst equipment were examined. This specimen grew up into a male mature medusa with a peduncle, eight marginal tentacles, and four oral tentacles branched twice on the 11th day after rearing, when it was 1.44 mm in diameter and 1.25 mm in height. Such morphology is the characteristic of the present species, however a further growth appeared successively, becoming to have 19 marginal tentacles and four oral tentacles branched four or five times, and the size attaining 2.5 mm in diameter and 2.1 mm in height. The tip of manubrium and the tentacular bulb were black in color, but no ocellus was present. Nematocysts of desmoneme and microbasic eurytele were found in the mature medusa. The present species closely resembles Bougainvillia aurantiaca BOUILLON, 1980 and B. muscoides (M. SARS, 1846) and their taxonomic relationship is discussed.
