Oxygen Consumption is Limited at an Ecologically Relevant Rearing Temperature in Pupfish Eggs

The habitat of the critically endangered Devils Hole Pupfish, Cyprinodon diabolis is marked by constant high temperatures and low oxygen availability. In order to explore the effects of these conditions on development and recruitment of eggs in Devils Hole, we tested the effects of two ecologically relevant temperatures on the development, hatch success, and oxygen consumption of eggs from a refuge population of pupfish derived from C. diabolis and eggs from its close sister species, Cyprinodon nevadensis mionectes. We developed a simple method to measure oxygen consumption in a single egg. Parent acclimation temperature, rather than incubation temperature, was the most important factor influencing hatch success. Eggs incubated at 33°C hatched more quickly compared to those incubated at 28°C. Despite this accelerated development, larvae from both temperatures were of similar size at hatch. Unexpectedly, eggs incubated at 33°C experience lower than expected oxygen consumption rates compared to those incubated at 28°C. Oxygen consumption rates would be limited at PO₂ values that are much higher than environmental oxygen tensions. Oxygen consumption increased dramatically upon hatch, indicating that low oxygen conditions such as those present in Devils Hole may limit developing eggs.