千葉県から得られた北限記録のオウギハゼとその分散要因

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書誌事項

タイトル別名
  • Northernmost record of <i>Bunaka gyrinoides</i> from Chiba Prefecture, Honshu Island, Japan, with a note on its dispersal

説明

A juvenile specimen of Bunaka gyrinoides (Bleeker, 1853) was collected from the Yoro River in Chiba Prefecture, Honshu Island, Japan. The specimen was characterized as follows: 15 branched rays in caudal fin; body cylindrical; foremost predorsal scales same size as others; head lacking sensory canal and pore; pelvic fin short, not reaching anal-fin origin; pectoral fin without upper free rays; scales present on top of head and upper gill covers; mouth large, cleft not exceeding anterior margin of eye; parietal scales small; predorsal scales ca. 33; anterior nasal canal short, its tip not reaching upper lip; sensory papillae on the cheek arranged longitudinally; no spines on anterior gill cover. The species is widely distributed in the Indo-Pacific region, and has previously been recorded from the Ryukyu Islands in Japan. The occurrence in Chiba Prefecture represents not only the first record from the Japanese mainland, but also the northernmost record of the species. Given the species is an amphidromous fish, this occurrence would be due to the natural dispersal of larvae via the Kuroshio Current from the south. Hitherto, reproduction of the species has not been confirmed in Japan; however, its dispersal to the Japanese mainland might have been facilitated in recent years by its reproduction area possibly moving northward.

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