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Round-trip Catadromous Migration in a Japanese Amphipod, Sternomoera rhyaca (Gammaridea: Eusiridae)

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Title: Round-trip Catadromous Migration in a Japanese Amphipod, Sternomoera rhyaca (Gammaridea: Eusiridae)
Authors: Kuribayashi, Keiko Browse this author
Katakura, Haruo Browse this author →KAKEN DB
Kyono, Masaki Browse this author
Dick, Matthew H. Browse this author →KAKEN DB
Mawatari, Shunsuke F. Browse this author
Keywords: adaptation
Issue Date: Sep-2006
Publisher: 日本動物学会
Journal Title: Zoological Science
Volume: 23
Issue: 9
Start Page: 763
End Page: 774
Publisher DOI: 10.2108/zsj.23.763
Abstract: We conducted a field study of the life cycle of the eusirid gammaridean amphipod Sternomoera rhyaca Kuribayashi, Mawatari, and Ishimaru, 1996 in a stream at Gokibiru, Hokkaido, Japan over the course of two non-consecutive years. This species is biennial; it spends most of its life in freshwater, but undertakes a short catadromous migration to the sea for reproduction. Reproduction occurs from March-June. Mature adults drift downstream to the sea singly and in precopulating pairs. Copulation and oviposition in the marsupium occur in mixed water at the stream mouth. Males die after copulation; ovigerous females return upstream by walking or swimming, where their eggs develop and hatch, after which the females also die. Juveniles remain in the stream, growing until they reach sexual maturity. Laboratory experiments showed that survivorship of all stages was lowest in seawater and highest in freshwater, though juveniles survived equally well in mixed water (50% seawater) and freshwater. Eggs developed to hatching only in freshwater; hatchlings in seawater and mixed water died within one and 21 days, respectively. Thus, S. rhyaca is well adapted to freshwater. Indeed, the only stages that required elevated salinity were copulation and subsequent oviposition, and we speculate that freshwater inhibits the female pre-reproductive molt. Because the life cycle of S. rhyaca has the most ontogenetically and temporally restricted saltwater phase known in any catadromous animal, its origin and maintenance are of evolutionary interest. We discuss two alternative hypotheses for the origin of the migratory life cycle, and discuss its maintenance in terms of fitness costs and benefits.
Rights: (c) 日本動物学会 / 本文献の公開は著者の意思に基づくものである
Type: article
Appears in Collections:理学院・理学研究院 (Graduate School of Science / Faculty of Science) > 雑誌発表論文等 (Peer-reviewed Journal Articles, etc)

Submitter: 片倉 晴雄

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