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

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Abstract
The mitotic rate of gastric mucosal epithelium in pond- and laboratory-reared Amblystoma punctatum larvae was determined at 2-hour intervals over a 24-hour period. In both groups of animals, the rate of cell division was characteristically cyclic showing maximum values between 10:30 a.m. and 12:30 p.m., and minimum values between 6:30 a.m. and 8:30 a.m. In pond animals, the daily over-all mitotic rate of gastric mucosa was 8 times that of the laboratory animals. Environmental differences between the pond and laboratory are suggested as the underlying cause for this differential in the mitotic rates of the two groups of animals. Since a similar, but greater, difference was previously found between the epidermal mitotic rates of the two groups, it appears that in the pond environment an enhanced general rate of growth is present which affects the mitotic rates of several tissue simultaneously. Gastric mucosa responds to a lesser degree than epidermis, indicating that in addition to an enhanced general growth rate in the pond environment, the epidermis may be responding to a greater degree than mucosa to direct exogenous environmental factors.