Life history of a goby, Gobius poecilichthys Jorfan et Snyder

Gobius poecilichthys Jordan et Snyder (1902), a small goby, some 80mm in total length, is found in tide-pools on the rocky coast of Southern Japan. Though Tomiyama, I.(1936) regarded this species, together with Bathygobius soporator(Cuvier et Valencinnes) of the south western coast of U.S.A., as synonyms of Gobius fuscus Ruppell(1928), I treat here this Japanese form provisionallu as a distinct species from the forms of other districts, wishing to compare its life history with others(Fig.1). The spawning season extends from June to September at Tomioka in the Amakusa Islands, Kumamoto Pref., Kyushu. The spawning takes place in tide-pools. The eggs are attached in one layer to the under side of a stone lying in the pool. The male parent fish guards the eggs until they hatch out, staying in the breeding-room prepared by himself under the stone. The fertilized egg is club-shaped with a shallow depression circling near its end, 1.8mm in length and 0.35 mm in width. The incubation-period is about 65 hours at the water-temperature of 23～27℃. The egg resembles in general appearance to that of Bathygobius soporator described by Breder, C.M.(1943) with slight differences in shape of the egg-membrane, attitude of the embryo and the incubation-period(Fig.2, A～L). The goby could be induced to spawn in a table aquarium provided with vacant shells of Pinna pectinata japonica Reeve for egg-layer. The newly hatched larva is about 2.3mm in total length. The larvae 6～18mm in total length appear in the tide-pool from August to November at Tomioka, which already entered into bottom-life feeding on planctonic copepods. The fishes over 20mm in total length live a bottom-life in the tide-pool all year round, feeding on moluscs and crustacean. The life-span of the fish seems to be over 4 years(Fig.3).冨山一郎（(1936）は，これ迄にアフリカ，紅海，印度洋，西南太平洋，ハワイ，濠洲北岸及び北米南西部等の各水域から採集された材料について，多くの著者によつて，夫々新種として報告されている．Gobius soporator Cuvier et Valenciennes, Gobius poecilichthys Jordan et Snyder 等の10種以上に上る類似のハゼを，総べてGobius fuscus Ruppell（1828）のSynonymとして，これにクモハゼという和名を附している．ここでは之等の種類の同異について論ずる事は出来ないが，筆者が熊本県及び鹿児島県から得た標本は総べてGobius poecilichthys Jordan et Snyder（1902, 模式標本は神奈川県三崎産）の記載とよく一致するので，こゝにはこの学名をクモハゼに用い，主として熊本県天草郡富岡町の海岸で1947年から1952年の間に行つた観察採集によつてここにクモハゼの生活史の概要を述べるが，Herre, A.W.（1927），Fowler, H.W.（１９２８），冨山 gobius soporator （Cuvier et Valencinnes）の産卵習性についてはBreder, C.M.（1943）の報告があり，これと注意して比較した．本研究に当り終始懇切なる御指導を賜わり，且つ現行の御校閲をお願した内田恵太郎教授並びに長期に亘る実験所の使用を御快諾下さり，また種々ご配慮を頂いた九大天草臨海実験所前所長相川広秋教授及び同所々員の方々，貴重な文献を拝借した松原喜代松博士，阿部宗明博士，並びに多数の貴重な標本を頂いた鹿児島大学今井貞彦助教授，当教室の大学院研究奨学生水戸敏の諸氏に深謝の意を表する