| Abstrakt: |
Thermal responses varied among four genetic stocks of juvenile largemouth bass: northern largemouth bass Micropterus salmoides salmoides (NLMB), Florida largemouth bass M. s. floridanus (FLMB), and both reciprocal F1hybrids, NLMB ? x FLMB ? (N x F) and FLMB ? x NLMB ? (F x N). Thermal responses for each stock were measured as the critical thermal maximum, the temperature at which death occurred during a temperature increase of 0.2°C/min, for fish at various acclimation temperatures (8, 16, 24, 32°C); and chronic thermal maximum, the temperature at which death occurred during a temperature increase of 1°C/d, for fish acclimated to 32°C. The rank order of values for both response measurements was identical for the four stocks: F x N > FLMB > N x F > NLMB. Increased acclimation temperature resulted in significant, proportional increases in the critical thermal maxima for all stocks. In addition, second-generation hybrid stocks (N x F F2and F x N F2) that were acclimated at 24°C produced similar critical thermal maximum values (38.4°C and 37.8°C, respectively) that were intermediate between those of the NLMB (37.3°C) and FLMB (39.2°C). Subsequent genetic analysis revealed no correlation between critical thermal maximum and genotype at the three enzyme loci studied (Mdh-B, Idh-B, and Aat-B). Thus, the subspecific origin of the alleles at these three loci had no detectable influence on the thermal responses of hybrid offspring. |
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