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1 August 2006 A Gastric-Brooding Asteroid, Smilasterias multipara
Miéko Komatsu, P. Mark O'Loughlin, Barry Bruce, Hideki Yoshizawa, Kanako Tanaka, Chisato Murakami
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The gastric-brooding asterinid sea star, Smilasterias multipara, broods from late August to early November in the shallow sublittoral zone of southeastern Australia. We observed males and females spawning in the laboratory. They shed gametes through gonopores on the sides of the arms. The eggs were orange, about 1.0 mm in diameter, and heavier than seawater. They were externally fertilized by sperm, and placed into the stomach of the female by the tube feet. Twenty-four hours after fertilization, the first cleavage occurred. Cleavage was equal, total, and radial. Development via a non-feeding lecithotrophic brachiolaria was direct, there being no planktrotrophic bipinnaria or brachiolaria larva. Embryos developed, through wrinkled blastula and gastrula stages, into brachiolariae with arms. All of the surfaces of the brachiolaria were covered by cilia. At metamorphosis, a starfish rudiment appeared on the posterior portion of the larval body, while the anterior portion of the larval body was absorbed. Two months after fertilization, metamorphosis was complete. After metamorphosis, juveniles in the stomach grew six pairs of tube feet in each arm. Juveniles, 3 mm in diameter, emerged from the mouth of the mother in early November. Developmental evidence suggests that this asteroid has evolved mechanisms for the protection of larvae and juveniles from gastric digestion.

Miéko Komatsu, P. Mark O'Loughlin, Barry Bruce, Hideki Yoshizawa, Kanako Tanaka, and Chisato Murakami "A Gastric-Brooding Asteroid, Smilasterias multipara," Zoological Science 23(8), 699-705, (1 August 2006).
Received: 20 December 2005; Accepted: 1 May 2006; Published: 1 August 2006
gastric brooding
larval development
Smilasterias multipara
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