Modulation of phenotypic traits under different rearing temperatures: Experimental evidence in male guppy (Poecilia reticulata)

Climate change particularly global warming unceasingly imposes a selective pressure in many organisms that results in phenotypic plasticity particularly by expressing different adaptive phenotypes to shifting environmental conditions. The present study was, therefore, conducted to explore the phenotypic responses of male guppy (Poecilia reticulata), a popular model fish, to an ambient (28±0.91°C), high (32±0.12°C) and low (22±0.17°C) rearing temperature. Almost equal sized juvenile males were collected from the wild and reared up to 30 days maintaining necessary conditions similar among treatments except the water temperature. The findings revealed that high-temperature reared fish had significantly lower number of courtships, reduced survival, decreased body size, deformed body shape, limited colour patterns and reduced sperm bundle number than the ambient- and low-temperature groups. On the other hand, low-treatment males performed significantly higher number of courtships than ambient-temperature group, while ambient-temperature reared males possessed significantly higher body size and iridescent colour area than low- temperature treatment. Interestingly, the findings also revealed some trade-offs between traits under thermal-induced stressed conditions (i.e. both high and low temperatures). These findings elicit further information about the thermal condition dependent expression of phenotypic traits of fishes which infer about how fish species will adapt in the predicted changing aquatic environments because of unprecedented climate change.