海蜇的生活史

THE LIFE HISTORY OF RHOPILEMA ESCULENT A KISHINOUYE

本文概述了海蛰 Rhopilema escylenta Kishinonye自受精卵、浮浪幼虫、螅状体、横裂体、碟状体至幼水母各发育阶段的形态学变化。首次报告了这个种的生活史。

The stages of development of the medusae, Rhopilema esculenta from fertilizedegg, planula, scyphistoma, strobila, and ephyra to young medusae were observed inlabolatory and described in this article. The medusae are dioecious. Fertilized eggs develop exteral to the parent body.planulae are formed 7 hours after fertilization. Most of the planulae metamorphose intoscyphistomae with four tentacles in 3 or 4 days, then 16 tentacles in 15--20 dayswhen the scyphistomae grow up. During the course of growth and after full growth,the scyphistomae continuously form podocysts, from which new scyphistomae bud out.It is a way of asexual reproduction. Two months later strobilation takes place attemplature 18--20℃. Generally a strobila can produce 6--10 ephyrae. A typical ephy-ra possesses 8 pairs of rhopalar lappets, 8 rhopalia and 4 gastric filaments. Lappet istalon-shaped and usually has 4--6 branches, the distance between the tips of the twosymmetrical lappets being 1.5--3.0 mm. It needs about 15 days for the young medusaeto grow to about 20 mm in diameter of the umbrella when cultured in laboratory, andmay attain 50 mm in diameter within 30 days. In the sea the medusae need 2 to 3months of growth from ephyra to maturity with umbrella 250--450 mm in diameterin the Liaodong Wan.