To elucidate the genetic control for thermal resistance of the guppy, its response to high temperature was measured as the death time, at which the immature fish acclimated at 23°C died when exposed to 37 °C. Using sub-population comparison, the heritability of thermal resistance was estimated at 0.183. The two-way selection for thermal resistance led to a significant difference of the death time of immature fish between the high temperature resistant population and the sensitive one. The resistant population showed a higher heterozygotic frequency at AAT-1∗ and PGM-1∗ locus than the sensitive population. This suggests a heterotic effect for thermal resistance and inbreeding depression for thermal sensitivity. Cross experiments confirmed heterosis for thermal resistance, supporting the above suggestion.
- isozyme marker
- thermal resistance