日本で初めて記録されたギヤマンハナクラゲTimoides agassizii (Anthomedusae, Pandeidae)の大量出現と刺症被害

Abstract

The blooms of a hydromedusa, Timoides agassizii (Giyaman-hanakurage in Japanese) occurred in July, 1999 and June, 2000 0ff the coast of Chinen-son, Okinawa, Japan. This is a new record of this species from Japan. Morphological observation was performed for 12 and 10 specimens collected in 1999 and 2000, respectively. Medusae collected in 1999 were larger (up to 44 mm in umbrella diameter) than those recorded previously from Maldive Islands and Papua New Guinea. Because the marginal cirri-like structures probably develop into the tentacles with growth, prospective tentacle is proposed as a proper term. The medusa (20 mm in diam.) collected in 2000 matured and produced planulae in a laboratory aquarium. We suggest that injuries reported from Chinen-son coastal water in 2000 must be caused by T. agassizii.