Notes on the Cleavage Rate of Scaphiopus bombifrons Cope, with Additional Remarks on Certain Aspects of Its Life History

Abstract

Field and laboratory studies of the life history of S. bombifrons were carried on for a period of 3 yrs. near Norman, Oklahoma. Breeding congresses occurred not earlier than Apr. 28, nor later than May 8. There is but a single breeding congress per yr. which is of only one night''s duration. The breeding dates appear to be directly correlated with the amt. of precipitation for the preceding 5 or 6 weeks and to be in response to a violent, heavy rain immediately preceding the breeding congress. The eggs are laid in temporary pools only and develop rapidly. In the laboratory the first cleavage of the zygote begins about 30 min. after insemination and the 5th cleavage is completed within 90 min. after fertilization. Gastrulation is completed in 8 hrs. and the larvae hatch within 30 hrs. after fertilization. The young larvae rest for 18-22 hrs. before they start to feed. Metamorphosis is completed within 35-38 days and begins when the tadpoles have a body-length of 16-19 mm. and a tail-length of 15-20 mm. During the first 4 days of larval life only algae are eaten. By the beginning of the 6th day the developing tadpoles must have meat included in their diet. Metamorphosis does not take place, however, if the tadpoles are fed exclusively on meat. Some greens as algae or lettuce appear to be necessary for normal development.