Larval Growth and Development of the Japanese Toad, Bufo bufo formosus, at Iwakura, Kyoto

Abstract

Yearly differences in the growth and development of the larval Japanese common toad, Bufo bufo formosus, growing in temporary pools in a swamp at Iwakura, Kyoto, were compared for the 1977 and 1978 seasons. Tadpoles showed more rapid development in 1978 than in 1977 due to a more delayed breeding season and subsequent higher water temperature in 1978. However, development of the 1978 larvae was retarded in the later period, resulting in similar embryonic and larval periods of 58-60 days in both years. Developmental retardation in 1978 was assumed to be the result of density effect. Tadpoles in 1977 had larger body sizes than those in 1978, especially in body weights, and such differences were presumed to be caused by a differential population density. Tadpoles delayed in development tended to have smaller body sizes than those reached at the same developmental stage earlier. Body proportions showed small yearly differences compared with absolute measurements, and were almost constant from Stages 31 to 39. This tendency indicates that body proportions are of value for systematic work. Larval survival at Iwakura was briefly noted: a female toad spawns ca. 5, 000 eggs, the average hatching rate being about 90.2%, and 5.5-20.2% of hatched embryos are assumed to complete metamorphosis. Whether the observed difference in metamorphic rates has significance is yet to be clarified.