ABSTRACT
The entire process of development from eggs to juveniles in the seastar, Luidia maculata, was observed. The breeding season of this sea-star in Tomioka Bay, Nagasaki Prefecture, Japan is in July. The eggs are transparent and 174 µm in average diameter. One and a half hours after fertilization, the first cleavage occurs at approximately 20°C. Embryos develop into a bipinnaria through the wrinkled blastula stage by total and equal cleavage. Metamorphosis takes place at the posterior portion of the bipinnaria 50 days after fertilization. At this stage, 9 spicules, corresponding to the rudimental terminal plates of adult skeleton, appear. One week later, full grown bipinnariae are 2.5 mm in length and have 5 pairs of bipinnaria arms. Sixty-four days after fertilization, metamorphosis is completed and resulting juveniles are about 700 µm in diameter. They have 9 arms like the adult and this seems to be related to the systematic position of L. maculata within the genus. The present observations show that L. maculata undergoes nonbrachiolarian type of development, like all species of Luidia previously reported.
