Nippon Suisan Gakkaishi 72 (1), 21-26 (2006)

Studies on the egg morphology and spawning season in the mirror-finned flying fish Hirundichthys oxycephalus in the waters near Kyushu, Japan

TOSHIO ICHIMARU,1 KOJI MIZUTA1a AND AKINOBU NAKAZONO2

1Nagasaki Prefectural Institute of Fisheries, Nagasaki 851-2213, 2Faculty of Agriculture, Kyushu University, Fukuoka 812-8581, Japan

Eggs of the mirror-finned flying fish Hirundichthys oxycephalus were collected from the drifts near Goto Islands and Yaku Island, from April to August within the years of 1998 to 2004. To identify species, the eggs were reared and the hatched larvae were observed. The eggs were 1.6-2.0 mm in diameter. Three types of filaments were recognized. One was a single filament of 20 μm, the others were 5-7 filaments of 10 μm, and 9-14 filaments of 6 μm. The number of filaments observed in H.oxycephalus was similar to that formerly reported in H.coromandelensis, however, the thinner diameter of H.oxycephalus filaments than that of H.coromandelensis makes it possible to distinguish between the two species. The eggs were collected in Kagoshima from May to July, and in Nagasaki from July to August, and this difference seems to be due to the difference of water temperature between the two localities.


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