Eggs, hatching and embryos variability in loggerhead sea turtle Caretta caretta show significant differences among nests coming from two Italian nesting grounds

Abstract

Analysis of embryonic asymmetry may inform on pathologies, metabolic deficiencies or on functional anomalies. In Chelonians, range and relative numbers of abnormalities that occur at the embryonic stages are poorly known. The relative importance of the abnormalities causing embryonic death in the context of the conditions of incubation is not known. As for Caretta caretta, very little information is available on the biometry and anomalies of dead embryos in the Mediterranean basin. We compared data on biometric variability of carapace length and width, flippers asymmetries, clutch size, and hatching success from nests of Loggerhead coming from: the Ionian Calabrian coast (Southern Italy), where nesting has longly documented, and the Northern Tyrrhenian coast (Tuscany, Central Italy), where nesting activity has started only recently. Dead embryos were found inside nests after hatchling emergence. The turtles that nested in the two areas laid similar clutch sizes, but the Northern Tyrrhenian coast shows less hatched eggs and a lower hatching success, higher number of dead embryos and of unhatched eggs. Embryos from the Northern Tyrrhenian coast were significantly smaller than the Ionian Calabrian ones. Estimated stages ranged from 26 to 31b in both regions, stages 29-31b were more abundant in the Ionian Calabrian. Left vs right fore-flipper length varied significantly, with left flipper being longer than right flipper, but this asymmetry did not differ between the two regions. Flipper asymmetry seems to be a shared pattern in both juvenile and adult stages, likely not being the cause of mortality of our studied embryos.