Testicular maturation indices (TMI) were determined for wild-caught males of Poecilia mexicana by quantitative analysis of the frequency of ongoing stages of spermatogenesis and spermatid differentiation in sections of testes stained with the Feulgen reaction for DNA. In nature, males maintain essentially constant levels of sperm production throughout the year and show no significant variations in mean TMI values associated with season, microhabitat, standard body length, or rank in male dominance hierarchies. Winter males or males isolated from females in the laboratory show accumulation of mature spermatophores. These findings suggest that fluctuations in the microstructure of wild populations of Poecilia from northeastern Mexico may be due primarily to differences in the temporal scheduling of female reproductive cycles and not to limitations imposed by sperm availability or male reproductive competence. The data are discussed in terms of competitive interactions within unisexual-bisexual breeding complexes involving the Amazon molly P. formosa, its related triploid hybrids, and the bisexual species, P. mexicana.
| Identifer | oai:union.ndltd.org:ETSU/oai:dc.etsu.edu:etsu-works-14520 |
| Date | 01 May 1981 |
| Creators | Monaco, Paul J., Rasch, Ellen M., Balsano, Joseph S. |
| Publisher | Digital Commons @ East Tennessee State University |
| Source Sets | East Tennessee State University |
| Detected Language | English |
| Type | text |
| Source | ETSU Faculty Works |
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