DEVELOPMENT OF THE SEA‐STAR, ASTERINA BATHERI GOTO

Abstract

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.

REPRODUCTION AND DEVELOPMENT OF THE HERMAPHRODITIC SEA-STAR,ASTERINA MINORHAYASHI

“…In A. batheri a few hermaphroditic individuals occur among gonochoric individuals (Ohshima, 1929). No difference seems to exist in the sexual status of this species from different geographical regions (Kano and Komatsu, 1978). In this study, it was found that A. minor is a spatial hermaphroditic and all individuals bear hermaphroditic gonads comprising both functional testes and ovaries.…”

“…Sexuality of asterinids has been fairly well studied since Cuenot (1887) reported the occurrence of protandric hermaphroditism in A. gibbosa. Among asterinid species, in addition to A. gibbosa, hermaphroditism is known in A. pancerii, A. batheri and A. scobinata (Ohshima, 1929;Cognetti, 1954;Dartnall, 1970;Kano and Komatsu, 1978). In A. batheri a few hermaphroditic individuals occur among gonochoric individuals (Ohshima, 1929).…”

“…The data accumulated so far indicate that genus Asterina, or its closely related groups, despite intimate similarity in adult morphology in different species, shows a remarkable variety in the mode of development and the method of breeding (Ludwig, 1882; MacBride, 1896; Goto, 1898; Mortensen, 1921;James, 1972;Komatsu, 1975;Kano and Komatsu, 1978). This observation may bring out the importance of studies on the development of Asterina group which may not only clarify the ontogeny of a given species but may also help towards understanding the evolution of asteroid development as a typical group having divergent breeding methods and development.…”

“…In general, asteroids whose development is direct have pear-shaped brachiolaria with three brachiolar arms. In species belonging to Asterina, the brachiolar arms of A. batheri and A. coronata japonica are short and blunt (Komatsu, 1975;Kano and Komatsu, 1978). The brachiolariae of these species have pelagic life.…”

Development of nervous systems to metamorphosis in feeding and non-feeding echinoid larvae, the transition from bilateral to radial symmetry

“…2001) and 3-4 days in sea star, such as Asterina batheri (Kano and Komatsu 1978). The NS formation was initiated by the appearance of a pair of nerve cell aggregates both on the left and right sides of the larval body that were linked with a bundle of axons by 4-day vestibula stage.…”