Effects of Water Temperature on Gonads Growth in Ambystoma mexicanum Axolotl Salamanders

SIMPLE SUMMARY: Amphibians are especially sensitive to temperature due to their lack of thermal regulation. Aquatic temperatures influence growth and development during the larval period and may impact sexual development. This study examined the rearing of axolotl salamanders from juvenile to adulthood at four temperatures to examine how this factor influenced reproduction output. Rearing temperature affected egg and testis production and indicates that males and females should be reared at different temperatures to optimize reproductive output. Additionally, axolotl salamanders may be especially sensitive to high temperatures suggesting that the reintroduction and translocation of axolotls into former and new habitats should identify water temperature as an important component in conservation efforts. ABSTRACT: The thermal environment is a major factor influencing amphibians. For example, amphibian reproduction occurs in specific temperatures, and minor changes in this aspect could have negative impacts on this biological process. Understanding the potential effects of temperature on reproductive output is important from both an ecological and captive breeding colony point of view. I examined temperature effects on reproduction in axolotl reared from egg to adult at 4 temperatures (15 °C, 19 °C, 23 °C, and 27 °C) These adult axolotls (n = 174) were measured and weighed, dissected, and their gonads were removed and weighed to obtain an individual’s reproductive allocation. Female axolotls reared at 23 °C had a greater Gonadosomatic Index (GSI) compared to axolotl reared at each of the other temperatures with axolotls reared at 27 °C having the lowest reproductive output. Moreover, all GSI pair-wise comparisons in the four temperature treatments were significantly different from each other (ANOVA, F (3, 66) = 61.681, p < 0.0001). Additionally male rearing temperature significantly influenced GSI (ANOVA, F (3, 89) = 10.441, p < 0.0001). Male axolotls reared at 19 °C had significantly greater GSI compared to males reared at the three other temperatures. There were no statistical differences among each of the other pair-wise comparisons. As seen in this experiment, axolotls may be especially sensitive to climate-driven warming due to their highly permeable skin and paedomorphic life history. Understanding how axolotls and other amphibian species adjust to the challenges of climate change is important in the management of this imperiled taxa.