KARYOPLASMIC STUDIES IN HAPLOID, ANDROGENETIC HYBRIDS OF CALIFORNIA NEWTS

¹ Department of Biological Sciences, Stanford University, Stanford, Calif.

Two species of West Coast newts differ strikingly in larval pigment patterns. Taricha torosa has a banded arrangement of the larval melanophores; in T. rivularis the larval melanophores are dispersed. Torosa is also characterized by a well developed balancer, whereas in rivularis the balancer is either absent or rudimentary.

1. Two of 54 heat-shocked, interspecific hybrids of T. rivularis x T. torosa were haploids. The two haploids are the first amphibian androgenetic, haploid hybrids to develop to stages where species characters could be observed.

2. The tissue and organ architecture of the heterospermic haploids conform to prior findings in homospermic haploids. The nuclei and cells are smaller and more numerous than in the diploid controls. A compensatory adjustment in cell shape as well as cell number was observed in single-cell layered organs.

3. The balancer was fully developed in the heterospermic haploids, thus indicating a strong directive influence of the nucleus (torosa) in the formation of this organ.

4. The larval pigmentation was dominantly like the nuclear-donor species in the number, degree of melanization, and pattern formation of the melanophores. No evidence was found of an influence on pigmentation by the cytoplasmic-donor species.

5. The above findings are discussed in relation to other studies on the roles of the nucleus and the cytoplasm in the differentiation of species characters.