Nonmodal scutes patterns in the Loggerhead Sea Turtle (Caretta caretta): a possible epigenetic effect?

Abstract

Eleven specimens of the threatened Loggerhead Sea Turtle (Caretta caretta (L., 1758)) were caught accidentally by fishermen in different parts of Sicily (Mediterranean Sea). Five of them showed an atypical number of carapacial and plastron scutes, making the immediate identification of the specimens as C. caretta difficult. Both genetic and epigenetic analysis were carried out on these specimens. Sequencing of a 649 bp sequence of the mitochondrial cytochrome c oxidase I (COI) gene allowed us to classify all the individuals as C. caretta. Epigenetic analysis, performed by evaluating the total level of DNA cytosine methylation, showed a reduced and significant (F = 72.65, p < 0.01) global level of methylated cytosines in the turtles with nonmodal scutes compared with the normal turtles. Our results suggest that the variability in the number of scutes could be dependent on the environmental conditions during embryonic incubation, via an epigenetic mechanism. This finding could have implications in our understanding of the pathways of morphological evolution and diversification in the chelonians.