Abstract
Male and female specimens of Hyla japonica were collected from a paddy field in a suburb of Niigata City in the breeding season (May), and naturally spawned eggs were obtained in the laboratory. The eggs were ca. 1.3mm in diameter. The eggs and embryos were reared under a constant temperature of 24C, which is the average water temperature in the paddy field in this period. 4.4 days after fertilization, the formation of the operculum was completed, and the larvae began feeding. Thereafter the larvae were reared at room temperature (24-29C). They were fed a commercial diet for goldfish. The larvae of this species are a nektonic type in external appearance, and the labial teeth formula is 1:1+1/3. Under the present rearing conditions, the total length of full-grown larvae was 47mm on the average. The larvae metamorphosed at the age of 32 days, and the body length of newly metamorphosed frogs was 14.5mm on the average. According to Gosner's table (1960), the process of development from just after spawning till the completion of metamorphosis is divided into 46 stages. The external characteristics in each stage are described in tabular form in English, and illustrated with sketches.
