THE CYCLIC NATURE AND MAGNITUDE OF CELL DIVISION IN GASTRIC MUCOSA OF URODELE LARVAE REARED IN THE POND AND LABORATORY

¹ Department of Anatomy, The Chicago Medical School, Chicago 12, Illinois

1. The mitotic rate of gastric mucosal epithelium in both pond- and laboratory-reared urodele larvae is cyclic over a 24-hour period. Maximum rate of cell division occurs in both groups between the hours of 10:30 A.M. and 12:30 P.M.; minimum mitotic activity is recorded between 6:30 A.M. and 8:30 A.M.

2. In pond animals, the mitotic rate of gastric mucosa is 8 times the rate of the mucosa of laboratory-reared animals. The environmental differences between pond and laboratory are suggested as the underlying cause for the differential in the rates of mitosis in the two groups of animals. Since a similar difference was previously found in the epidermal mitotic rates of the same animals, it is suggested that in the pond environment an enhanced rate of growth is present.

3. The difference between the pond and laboratory mucosal daily mean mitotic rate is of lesser magnitude than the difference between the epidermal rates of the same animals. This fact indicates that the epidermis may be responding directly to exogenous environmental factors, whereas the mucosa responds only to a lesser degree since it is not directly exposed to the environmental factors.