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Asterina pseudoexigua pacifica is a true ovoviviparous asteroid in that its development and metamorphosis occur within the spatial hermaphroditic gonad. From the middle of June to the middle of July, the gonad contains numerous embryos and juveniles in various stages through metamorphosis. The opaque, greenish yellow mature ovum is 450 μm in diameter. Development is direct. Embryos develop through wrinkled blastula and gastrula stages into a pear-shaped brachiolaria with three arms. The general process is similar to that of asteroids having direct development. Newly metamorphosed juveniles are released from the gonopores. Peak release occurs in the middle of July. The maximum number of juveniles released from an adult is about 1300. The juvenile is 900 μm in diameter and has two pairs of tubefeet in each arm; the skeletal plates are well developed. The present results are compared with those of other true viviparous echinoderms.

Using natural spawning and artificial fertilization, the entire process of development from eggs to juveniles was observed in the sea-star, Asterina batheri Goto.The breeding season of this animal in Tsukumo Bay and Toyama Bay is estimated to be late summer. The spawned eggs are approximately 430 pm in diameter and float near the surface of sea water. Tliey develop, through a wrinkled blastula stage by holoblastic, radial cleavage, into a pear-shaped brachiolaria bearing 3 blunt brachiolar arms. Metamorphosis takes place while the brachiolariae are swimming. Ten days after fertilization, metamorphosis is complete; the resulting juveniles are about 800 pm in diameter and colored pale brown with a green tint. They bear 2 pairs of tube-feet and a terminal tentacle in each arm.Development of this species is thus of the direct type, and very similar in every respect to that of Asterina coronata japonica, which is closely related to the present species.

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