Apocryptodon bleekeri (DAY) is a small gobioid fish. some 70 mm in total length, andcylindoric in body-form with small eyes. It is distributed to warm zones from India to thesouth-eastern Asia. In Japan it has been collected from coastal zones of Kasaoka City, InlandSea, and Ariake Sound and Yatsushiro Sea both in Kyushu. It is rather aboundant in the innerpart of Ariake Sound, and caught with various set-nets operating there during warm season.In the Ariake Sound it is frequently observed at the ebb that the gobioid fish lived in thehole of a kind of shrimp, Alpheus bis-incisus (de HAAN)t,o gether with the host (Text-Fig. 1).Sometimes the fish concealed itself in the holes of crabs and one other gobioid fish,Odontambl yopus rubicundus. The fish fed on mud and diatoms. The intestine is narrow andgreatly coiled and longer than body-length. It seems that the fish feeds on diatoms, growingon mud-bottom, at the flood when the bottom is covered with sea-water. Altenatly one othergobioid fish, Boleophthalmus chinensis, feeds on the same diatoms at the ebb when thebottom is exposed in the air.The spawning-season s e ems to extend from May to July, during rainny season, in AriakeSound. The sex-dimorphism devloped in the form of, genital papilla. A light black nuptialcoloration appeared on the ventral fin and anal fin in both sexes. The, fertilized egg is notcollected yet. The artifical insemination have been carried out several times, but it can notattain success. The number of ripe ovarian eggs was enumerated 592 to 5,826 (Table 1). T hedischarged unfertilized egg is ellipsoid form, 1 mm in long axis and 0.5 mm in short axis,with a bundle of adhesive threads at the basal end (Text-Fig. 2, A).The larvae, 10 to 20 m m in total length, were caught with set-n e t of fine mesh operatingin estuary during July to September, about 2 months after the spawning-season (Text-Fig. 2,B, C). These translucent larvae seemed to live a swimming life in coastal zone. Copepodswere detected from the simply cioled intestine of the larva in swimming life (Text-Fig. 2,F, G). The larva resembles that of Boleophthalmus chinensis in general facies, but it can bereadily distingushed from the other by the characteristic series of melanophores at the baseof anal fin. The 20 mm juvenile entered into a bottom life at shallow pool on tidal mudflat(Text-Fig. 2, D). Copepods and organic detritus were detected from the simply coiledintestine of the juvenile (Text-Fig. 2, H). The 23 mm young with coiled intestine li ved abottom-life and fed on diatoms and mud (Text-Fig. 2, I, J).From the examination of over 200 specimens coll e cted it seems that the fish grow to over　55　mm　and　become　mature　in　2　years　as　two　other　herbivorous　gobioid　fishes，　SicyoPterusJ’aPonicus　and　BoleoPntkalmus　chinensis．

長崎大学水産学部研究報告, v.10, pp.133-139; 1961