Geometric morphometrics, scute patterns and biometrics of loggerhead turtles (Caretta caretta) in the central Mediterranean

We investigate for the first time allometric vs. non-allometric shape variation in sea turtles through a geometric morphometrics approach. Five body parts (carapace, plastron, top and lateral sides of the head, dorsal side of front flippers) were considered in a sample of 58 loggerhead turtles ( Caretta caretta ) collected in the waters around Lampedusa island, Italy, the central Mediterranean. The allometric component was moderate but significant, except for the plastron, and may represent an ontogenetic optimization in the case of the head and flippers. The predominant non-allometric component encourages further investigation with sex and origin as potential explanatory variables. We also reported the variation of marginal and prefrontal scutes of 1497 turtles, showing that: variation of marginals is mostly limited to the two anteriormost scutes, symmetry is favored, asymmetry is biased to one pattern, and the variation of marginal and prefrontal scutes are linked. Comparisons with other datasets from the Mediterranean show a high variability, more likely caused by epigenetic factors. Finally, conversion equations between the most commonly used biometrics (curved and straight carapace length, carapace width, and weight) are often needed in sea turtle research but are lacking for the Mediterranean and are here estimated from a sample of 2624 turtles.