The bionomics and larvae of the two gobioid fishes, Ctenotrypauchen microcephalus (Bleeker) and Taenioides cirratus (Blyth)

Ctenotrypauchen microcephalus (Bleeker) is a blind, red gobioid fish synonymous with Trypauchen wakae Jordan et Snyder (Fig. 1). The burrowing-habit of this gobioid fish was not recognized with certainty in this research at the natural habitat. The spawning-season seems to extend from June to August in the innermost part of Ariake Sound and in Inland Sea. Neither spawned eggs nor spawning habit yet is known. The ripe ovary contains two groups of eggs, the ripe egg-group, 0.51～0.65 mm in diameter, and the unripe ones, less than 0.17mm. The number of the ripe ovarian eggs was enumerated as 1,477～2,413 in three individuals (Table 1). The ripe testes are whity band-like in shape lacking adjunctive organ (Seminal vesicle : Weisel, G. F. 1949). The larvae, less than 8 mm in total length, are not yet obtained. The postlarvae, 8～15 mm, were collected together with other fish larvae and small shrimps from July to October with set-nets put in the water-course of estuary of Ariake Sound. These postlarvae are elongate and laterally compressed in shape, provided with normally developed eyes, 35 (10+25) myotomes, large air-bladder, fan-like pectoral fins, lacking chromatophore (Fig. 2). They are translucent when alive, but become opaque and white after preserved. These postlarvae gathered under the light at night in the natural habitat of Inland Sea. After the swimming life has passed they enter into the bottom life at the size of 20 mm in total length when the juvenile stage begins. Only soft mud was detected from the alimentary duct of the adult fish collected from Ariake Sound. From the examination of size frequency of the specimens collected from Ariake Sound, this gobioid fish seems to grow over 85 mm in total length in a year, and some individuals become mature. A few individuals seem to live over three years. Taenioides cirratus (Blyth) is a blind eel-like gobioid fish synonymous with Taenioides lacepedei (Schlegel) (Fig. 3). The number of the ripe ovarian eggs of a mature female, 187 mm in total length, is enumerated as 20,126 (Right ovary 10,168+Left ovary 9,958). The ripe testes are whity and band-like in shape with small leaves of the adjunctive organ. Neither spawned eggs nor spawning habit is yet known. The spawningseason seems to extend from June to September in the innermost part of Ariake Sound. based upon the examination of the ovarian eggs and the collection of larval fish. The larvae, less than 9 mm in total length, are not yet obtained. The postlarvae, 9～15 mm in total length, were collected from July to October with set-nets, put in the water-course of estuary of Ariake Sound (Fig. 4). The postlarvae were swimming and gathered under the light at night in the natural habitat of Inland Sea. They are elongate and laterally compressed in shap, provided with normally developed eyes, large air-bladder, 32 (10+22) myotomes and a few melanophores at the base of the caudal fin. After the swimming life has passed this gobioid fish enters into bottom life at the size 15 mm in total length when the juvenile stage begins. The juveniles are eel-like in shape, with the eyes half buried under the skin. No food particle was detected from the alimentary ducts of the postlarvae.アカウオ Ctenotrypauchen microcephalus (Bleeker) およびチワラスボ Taenioides cirratus (Blyth)は共にハゼ亜目Gobiinaのワスラボ科Taenioidaeに属する特異な形態を示すハゼで, 東南アジア, 印度の各地に広く分布することが知られ, 日本では南部各地の内湾に棲むことが報告されている. ここでは主として瀬戸内海および有明海から得た材料によつてこれらのハゼの形態, 生態および幼期について述べる