Shaping hatchling fitness through maternal and environmental influences in green sea turtles

Sea turtles have no parental care, making maternal investment and environmental conditions crucial for offspring fitness. The morphological characteristics of hatchlings and the size of residual yolk after hatching are important indicators of neonatal viability. However, considerable geographic variation exists, and the impacts of maternal and environmental factors on hatchling morphology, residual yolk mass, and behavior performance are not yet fully understood, especially in the Western Pacific Ocean. This study investigated the effects of nesting green sea turtles (Chelonia mydas), clutch variables, and environmental variables on hatchling morphology and the size of the umbilical scar (an indicator of residual yolk mass) to estimate post-hatching energy reserves, as well as to evaluat how these morphological indicators influence hatchling behavior on Taiping Island in the South China Sea. Our results showed that larger nesting green sea turtles laid larger and heavier eggs. In the mixed-effects model, individual differences among nesting green sea turtles influenced the morphology and performance of their offspring. The hatchling morphology was positively associated with egg size and the distance between the clutch location and the highest high tide line. The size of the umbilical scar was positively associated with clutch temperatures during the last incubation window, but inversely correlated with temperatures during the middle incubation window. Additionally, the time required for hatchlings to complete a self-righting test was positively correlated with the umbilical scar width but inversely correlated with straight carapace width. These findings highlight the complex interplay between maternal investments and environmental conditions in shaping the fitness of green sea turtle hatchlings. Understanding these relationships provides valuable insights into potential mechanisms of survival and energy reserves of sea turtle offspring.