魚類学雑誌
Online ISSN : 1884-7374
Print ISSN : 0021-5090
ISSN-L : 0021-5090
ニセヨーロッパタナゴRhodeus pseudosericeusの初期発育
鈴木 伸洋
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ジャーナル フリー

2006 年 53 巻 1 号 p. 47-54

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After hatching from eggs deposited in the gill cavity of freshwater bivalves, bitterling larvae undergo initial development in the bivalve before adopting a free-swimming mode. This study examined the early ontogeny of Rhodeus pseudosericeus, collected from the Som River, part of the Namhan River system in South Korea. Ripe unfertilized eggs and larval development were observed in a controlled water temperature (22±1°C), the eggs being rather pear-shaped with an opaque yellow yolk, measuring ca. 3.1 mm in length and 2.2 mm in breadth. Larvae of R. pseudosericeus are characterized by a pair of wing-like processes on the yolk, which is anteroventrally convex, as in other Rhodeus larvae, until an advanced stage (i.e., 9 day-old). The anterior region of the yolk sac at hatching is hollowed, unlike the spherical triangular shape in most other Rhodeus larvae and broad spheroid in R. spinalis. Rhodeus pseudosericeus larvae began to feed when the free swimming stage was reached. Dorsal and anal fin rays were formed completely by 24 or 25 days after hatching. Melanophores aggregated anteriorly onthe dorsal fin became a trapezoid-like black spot in the juvenile stage (i.e., 54 day-old), elliptical in R. atremius atremius, R. atremius suigensis, R. notatus, cresentic in R. ocellatus ocellatus, R. ocellatus kurumeus, roughly rectangular in R. sinensis and round in R. spinalis. Minute tubercles on the skin surface in R. pseudoseriseus shared similar morphology with those of other Rhodeus species.

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