Delayed Reproduction in Amblystoma Punctatum.

Abstract

Nine specimes of adult Amblystoma punctatum, captured in pools in the Pocono Mountains, near the village of Effort, Pennsylvania, During the breeding season (the first week of April) of 1929, were kept in the laboratory of the Morris Biological Farm of the Wistar Institute until February 14, 1930, when they were placed in a mechanical refrigerator. On May 28 two females and one male were found frozen to death. The others of the lot, one female and 5 males, were placed in an aquarium. On the morning of May 29 numerous spermathecae were found deposited on sphagnum in the aquarium, and during the night of May 29-30 two clutches of eggs were deposited. On the morning of May 31 another clutch, very small, was found, but it was probably deposited on the first night, for the eggs did not appear to differ from the others in degree of development.

The effs were examined critically on June 7. There proved to be 125 in all. Seventy-six of these were developing normally in various neural groove and early tube stages (Harrison's stages 15 to 19); 36 were abnormal, mostly in an apparently abortive segmentation (possibly parthenogenetic); 11 were apparently infertile. The normal embryos progressed in development accoridng to Harrison's stages approximately as follows: June 10, stage 26; June 11, stage 27; June 12, stage 31; June 13, stage 31+; June 15, stages 32 and 34; June 16, stage 34; June 17, stages 34 and 35; June 18, stages 35 and 36. On June 15, 9 were in the early flexure stage (Harrison's stages 33 and 34); 18 in the non-motile stage (Harrison's stages 33 and 34); the others were in the premotile stage.