Biol. Bull.
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Biol. Bull. 215: 89-97. (August 2008)
© 2008 Marine Biological Laboratory

Morphology and Gene Analysis of Hybrids Between Two Congeneric Sea Stars With Different Modes of Development

Kaori Wakabayashi1,*, Miéko Komatsu1, Manabu Murakami2, Isao Hori3 and Tsutomu Takegami2

1 Graduate School of Science and Engineering, University of Toyama, 3190 Gofuku, Toyama 930-8555, Japan
2 Division of Molecular Oncology and Virology, Kanazawa Medical University, Uchinada, Ishikawa 920-0293, Japan
3 Division of Biology, Kanazawa Medical University, Uchinada, Ishikawa 930-0293, Japan

* To whom correspondence should be addressed. E-mail: d0671309{at}ems.u-toyama.ac.jp

The sea star Astropecten scoparius has feeding bipinnarian larvae, whereas its congener Astropecten latespinosus has nonfeeding barrel-shaped larvae. To investigate evolutionary changes in the development of asteroids, we performed reciprocal crosses between these two species with different larval forms. In the cross between A. scoparius eggs and A. latespinosus sperm, embryos developed into bipinnaria-like larvae. The larvae exhibited either a functional digestive system (a maternal feature) or a nonfunctional digestive system with the tip of the archenteron not connected to the stomodeum (a paternal characteristic). However, in the reciprocal cross between A. latespinosus eggs and A. scoparius sperm, barrel-shaped larvae resembling those of A. latespinosus were produced, in addition to bipinnaria-like larvae, some with functional digestive systems and some with nonfunctional ones. Juveniles were produced from all types of crosses. 18S rDNA was used as a gene marker in cycle sequencing analysis to investigate the genetic features of these juveniles. The sequences of juveniles from bipinnaria-like larvae showed double-peak nucleotide signals, indicating a biparental genome. On the other hand, juveniles from barrel-shaped larvae from A. latespinosus eggs and A. scoparius sperm showed the same sequence as A. latespinosus juveniles. This suggests that bipinnaria-like larvae of both crosses are always hybrids, whereas barrel-shaped larvae develop parthenogenetically.

Abbreviations: As x Al, cross-fertilization between eggs of Astropecten scoparius and sperm of Astropecten latespinosus • Al x As, cross-fertilization between eggs of Astropecten latespinosus and sperm of Astropecten scoparius






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