Effect of Maximal Feeding on Metamorphosis in Amblystoma

Abstract

Twitty and Schwind have shown that in heteroplastic grafting between the 2 species Amblystoma tigrinum and A. punctatum, comparable results with respect to growth are obtained only when the hosts are all maintained at the same nutritional level, an effect obtained by maximal feeding, thus insuring the rapidly growing voracius tigrinum larvae opportunity to realize their full capacity for growth. The effect of maximal feeding upon the more slowly growing species has not been emphasized, although various workers have noted that along with the spectacular acceleration of the growth rate, and a consequently earlier metamorphosis, there is a high mortality during the metamorphic period in maximally fed groups of A. punctatum, regardless of the type of diet. The present experiments were undertaken in order to show the results of quantitative variation in a single diet upon the developmental rate and viability of A. punctatum from the earliest feeding stage through metamorphosis. Two hundred animals, taken from several bunches of eggs all at approximately the same stage of development, were reared from stage 39 onward in separate finger bowls. At the feeding stage the animals were divided into 4 groups of 50 each. The first 50 animals were starved, the second group given one feeding weekly, the third fed 3 times a week, and the fourth fed maximally. Enchytraeus, a small white worm, was used as the sole diet. All animals were measured at approximately 2-week intervals, the total length being recorded.