ヒゲミミズハゼ

Lucigobius saikaiensis Dotu is a small elongated gobioid fish, blackish brown in coloration, and attaining some 36 mm in total length. It resembles to Luciogobius guttatus Gill (Jordan D. S. and Snyder, J. 0. 1901, D 3tu, Y. 1957 b ; Fig. 1 A, B). Specimens of this goby have been obtained from limited areas on rocky coasts, facing the open sea of the Amakusa Islands and the Tsushima Islands, both in Kyushu. In the natural habitat this goby was found to carry a bottom life, hiding under stones lying on the sandy bottom. The sex dimorphism is slightly observed in the form of the genital papillae. The ripe testis in a translucent narrow band with a small adjunctive organ at its posterior end (Weisel, G. F. 1949). The ripe ovary contains two groups of eggs, namely the orange-colored mature egg-group, 0.63～0.80 mm in egg diameter, and light yellow or translucent inmature group, 0.07～0.30 mm in egg diameter. From the similarity of the external features of the mature ovarian eggs, they seemed to be spawned at a time. The number of mature ovarian eggs was enumerated as 66～127 in five individuals examined (Table 1). The spawning-season seemed to extend from March to April on the coast of the Amakusa Islands. The spawning was carried out in the above-mentioned natural habitat. The spawned eggs were attached in one layer to the under side of the stone lying on the bottom sand. The number of the spawned eggs of one brood was enumerated as 85, 91, 130 and 131 in four cases. The spawned eggs are elongated spindle shaped, 2.9～3.0 mm in long axis and 1.2～1.4 mm in short axis. They are demersal and adhesive, with a large perivitelline space and a bundle of adhesive filaments at its basal end (Plate 20 A～F). The incubation period extended about the ten days at 15～20℃. The newly hatched larva is 4.5 mm in total length, strongly resembling to the larva of L. guttatus Gill. The larva completely consumed its yolk in seven days (Plate 20 L). The hatched larvae were reared in a glass-jar for thirty-two days. In this rearing-period the larvae were chiefly fed with small living planktonic copepods collected from the coastal zone with a plankton net. They grew to 12.2 mm in total length in this period (Plate 20 I～K). The postlarvae, 8～15 mm in total length, were found to live a swimming life in a same shoal with the larvae of another gobioid fish, Chasmichthys gulosus (Guichenot) of the same size in the littoral zone near the spawning-ground (Plate 20 L). The gut-contents of these larvae consisted of small planktonic copepods , other crustacean larvae and fish larvae, whereas that of the adult fish consisted of creeping copepods and isopods. From the examination of size-frequency of the collected specimens, this gobioid fish of the Amakusa Islands seems to attain about 35 mm in total length in a year and become mature. From the comparition of the body-form, bionomics and life history of Luciogobius saikaiensis and its allied L. guttatus, the author came to the conclusion that the former species more specialized than the latter (Dotu, Y. 1957a, 1957 b).