Best swimmers hatch from intermediate temperatures: Effect of incubation temperature on swimming performance of olive ridley sea turtle hatchlings

Marine turtle hatchling survival depends not only on suitable incubation temperatures allowing for viable embryo development but also adequate locomotor capacity to avoid predation while crawling from the beach to the sea and when swimming into the open ocean. To investigate the effects of temperature on swimming performance of olive ridley (Lepidochelys olivacea) hatchlings, we incubated eggs at different constant temperatures (24-34 degrees C) using a split-clutch approach. Swimming performance of hatchlings was tested and video-recorded for 24 h in static water under a day/night cycle (experiment 1) and for 30 min in continuously flowing water in the dark (experiment 2). Data from experiment 1 were evaluated visually to estimate the time of swimming activity. For experiment 2, we used software to calculate movement parameters from which hatchling performance was estimated. In both experiments, intermediate incubation temperatures (28-30 degrees C) were optimal not only for hatchling success and morphological dimensions but also for swimming performance, with 30 degrees C being the most favorable. Performance from hatchlings diminished with higher and lower temperatures, especially at the coldest range (26-27 degrees C). Phenotypic plasticity was observed from low and high incubation temperatures, with higher variation in performance among hatchlings from eggs incubated at 26-27 degrees C and 32-33 degrees C than for those incubated at 28-30 degrees C. Our results consistently showed that incubation temperature exerts the greatest influence on swimming performance and that maternal origin (clutch) has a significant effect on individual hatchling morphology. Given that the olive ridley year-round breeding leads to variable nest incubation temperatures in hot summers and cooler winter months, our results highlight the need for careful temperature management to produce hatchlings with optimal swimming capacities and, hence, highest survival probabilities.