Skull ontogenetic variation of the coastal developmental stage of the loggerhead turtle (Caretta caretta) in the western South Atlantic Ocean

The present study aims to describe the ontogenetic changes in the skull of the loggerhead turtle, Caretta caretta by focusing on the stages of development in the western South Atlantic Ocean. Our hypothesis is based on the premise that changes in feeding habits will reflect changes in the shape and/or size of the skull. The existence of changes in skull of the loggerhead turtle were analyzed using traditional and geometric morphometrics on skulls collected from stranded individuals in the southern Brazilian coast. As a general result, a transformation pattern was observed: from younger specimens with smaller, elongated and flattened skulls towards a larger, rounded and more robust skull in older specimens. It is suggested that these skull changes are associated with the diet shift of the loggerhead turtle specimens, providing the skull with greater mechanical resistance and enabling a change in feeding strategy from soft organisms to hard-shelled preys. This result highlights the importance of southern Brazilian coast for the life cycle of the loggerhead turtle. In this region, the individuals undergo the process of ontogenetic diet shift, changing their skull shape to adapt to the newly occupied niche and ensuring the ecological success of the species.