| Budget Amount *help |
¥2,100,000 (Direct Cost: ¥2,100,000)
Fiscal Year 1992: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1991: ¥1,600,000 (Direct Cost: ¥1,600,000)
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| Research Abstract |
(1) In this study, the development of Luidia maculata Muller et Troschel, through metamorphosis was observed. The eggs are 173 mum in diameter. One and half hours after fertilization, cleavage is total and radial. Embryos develop into a bipinnaria through the wrinkled blastula stage. Metamorphosis takes place gradually at the posterior portion of the bipinnaria, 40 days after fertilization. At this stage 9 spicules, corresponding to the terminal plates of adult skeleton, appear. One week later, bipinnariae reach a length of 2.5 mm. Sixty-four days after fertilization, metamorphosis is completed and resulting juveniles are about 700 mum in diameter. They have 9 arms and bear 2 pairs of tube-feet in each arm.
(2) This study shows the ontogeny of the present species may be correlated to the phylogenetic relationships of the species of Luidia in the following features. 1.Development of the present species is the non-brachiolarian types as all species of this genus previously reported. 2. The present observations comfirm Mortensen's view (1938) on the parallelism between the form of the bipinnaria, and the systematic position in the genus. Because bipinnaria of the present species belonging to the 2ndly advanced Alternata group (Doderlein 1920) has less one pair of bipinnaria arms than those of L. quinaria, which is included to the 3rdly advanced Quinaria group. 3. Because of just metamorphosed juvenile bearing 9 arms like the adults, the time of arms formation in multiarmed species of asteroid is related to the systematics of Luidia species.
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