Embryonic Mortality Across the Developmental Stages of the Green Turtle (Chelonia Mydas) on Lanyu Island, Taitung County, Taiwan

Green turtle (Chelonia mydas) embryogenesis can be separated into 31 stages, each with a unique set of morphological characters. During embryonic development, the environment in which embryos develop can influence their mortality. However, little is known about which embryonic stages are particularly sensitive to environmental factors, and which environmental factors significantly influence mortality.

In 2017 and 2018, we relocated and monitored 33 recently oviposited C. mydas nests, using data loggers to record nest temperature, air temperature, and precipitation. Upon hatchling emergence, we sampled nests to estimate stages at which embryonic mortality occurred. Three environmental factors were measured—nest temperature, net nest temperature (defined as the rise of nest temperature by the metabolic heat produced during embryogenesis) and precipitation- and net nest temperature was found to have the greatest impact on mortality. Net nest temperature can reach the highest value of incubation, sometimes even exceeding the safe incubation temperature range. The highest mortality was probably caused by high temperatures because the greatest mortality and highest temperatures coincided at the end of incubation, which may exceed the capacity of heat shock protein of embryos.

Keywords:Green turtle; Embryogenesis; Mortality; Nest temperature; Net nest change