Oocytes of the orange-red type female of the medaka, Oryzias latipes were isolated 2-3 hours before the germinal vesicle breakdown.They were cultured in vitro in various media and germinal vesicle breakdown, ovulation, and development upon insemination were observed.The medium suitable for oocytes to acquire the developmental capacity was selected from various media.There appeared to be little effect of glucose (0.5-2 mg/ml) or sodium pyruvate (0.1-2 mg/ml) in the external medium on the oocyte maturation. Oocytes could mature in the presence of bovine serum albumin in Yamamoto's salt solution, although they failed to mature in Yamamoto's salt soultion without bovine serum albumin. Bovine serum albumin was dispensable for the medium which was finally selected for oocyte culture.Composition of salts in the most suitable medium was as follows: NaCl 6.5 mg/ml, KC1 0.4 mg/ml, CaCl2·2H2O 0.15 mg/ml, and adjusted by N/10 NaHCO3 to pH 7.3.
A young of Holacanthus tritnaculatus Lacépéde was kept alive for 104 days in an aquarium.The specimen was collected in Suruga Bay, Japan, on November 11, 1972.The specimen represents the first record of this species from Suruga Bay.The change in the color pattern with growth to described here first time for this species. Some differences in characters are noted between the former description of this species by various authors (especially Fraser-Brunner, 1933) and 5 adult specimens collected in Japan.
A cetomimiform fish, Barbourisia rufa Parr were hitherto known from Gulf of Mexico, Madagascar, . and north-west Pacific (Kurile Islands and Hokkaido).A female specimen (193 mm in total length) was collected by a deep-trawling in the water 692-715 m drawn from 39°32.4': 142°23.7, to 39°48.8': 142°30.5'.The morphometric and meristic characters of the present specimen agree with those records.The locality where the fish was collected is southernmost in the waters of Japan; further southern extention of the record is anticipated.
The sea-run form of the Dolly Varden (Salvelinns malma) has not been recorded from Hokkaido, excepting two anadromous males (Flikita, 1962; Ishigaki, 1967).On April 23rd, 1972, a silvery specimen of the Dolly Varden, immature female and 153.1 mm in total length, was collected from the Shoji River in the Shiretoko Peninsula, northeastern Hokkaido. It was identified as a smolt of the Dolly Varden, and is a new record from Hokkaido. The tip of the dorsal fin was jet black and posterior margin of the caudal fin was faintly edged with black. No significant differences were recognized.in the number of vertebrae, pored scales, pyloric caeca, and gill rakers, between the smolt and river resident form from the same district. It was considered, from the point of geographical variation of the fish and geographical aspects of the Shiretoko district, that the fish might have hatched in the Shoji River.