DEVELOPMENT AND SURVIVAL OF HAPLOIDS OF THE MEXICAN AXOLOTL, AMBYSTOMA-MEXICANUM

Gynogenetic haploids of the Mexican axolotl, Ambystoma mexicanum, were produced by artificial insemination of eggs with ultraviolet‐irradiated sperm. Initially, haploids developed more rapidly than control diploids, and had twice the number of cells by 12 hours. Thereafter, development was slower, but haploids maintained a 2:1 ratio of cell number at the same morphological stage. In both haploids and diploids, division was rapid up to gastrulation, at which point the rate decreased 40‐ to 50‐fold. Prehatching mortality of haploids was greater than that of control diploids, but for both, the pattern appeared related to that of cell division; embryonic mortality was highest in the first few days, and then decreased substantially. Though nearly 50% of the haploids did survive to hatching, most failed to feed, and those that did were generally abnormal in appearance, and did not survive to maturity. The results suggest that prehatching mortality can be blamed neither on the expression of deleterious recessives nor on a reduced nucleocytoplasmic ratio. Copyright © 1979 Wiley‐Liss, Inc., A Wiley Company