Metabolic Rate Differences in Amblystoma Larvae.

Abstract

Variations in the growth rates of homoplastic and heteroplastic grafts on Amphibia have been observed by many workers. Harrison, 1 for example, noted the retardation and acceleration of heteroplastic grafts in Amblystoma larvae. Differences in the metabolic rates existing between species would seem to afford a partial explanation, at least, for such results. Tests were designed, therefore, to determine the metabolic rates of 81 Amblystoma larvae involving 4 species of Amblystoma, and the strain commonly spoken of as “Axolotl.”

The metabolic rates were based on the oxygen consumption for 4 hours, as determined by the Winkler method. All tests were run at 20° C., while all other factors affecting the metabolic rate, such as food and activity, were controlled. An abbreviated resumé of the results follows:

10 A. punctatum averaged a 46.9 per cent higher rate than 10 A. tigrinum.

12 A. punctatum averaged a 47 per cent higher rate than 12 A. tigrinum.

10 A. punctatum averaged a 24 per cent higher rate than 10 A. jeffersonianum.

10 A . microstomum averaged a 104.2 per cent higher rate than 10 A. punctatum.

17 A. tigrinum (Axolotl) averaged a 3 per cent higher rate than 12 normal A. tigrinurn.

It is apparent, therefore, that considerable differences in metabolic rate do exist between the four species of Amblystoma larvae tested, the order in point of highest rate being: A. microstomum, A. punctatum, A. jeffersonianum, A. tigrinwm. Such marked differences, substantiated by biornetrical analysis, lead one to the general conclusion that the abnormal acceleration of heteroplastic grafts is due partially, at least, to the influence of a higher metabok rate than the graft was accustomed to.