Hybridization of the Green Turtle (Chelonia mydas) and Hawksbill Turtle (Eretmochelys imbricata) in the Pacific Ocean: Indication of an Absence of Gender Bias in the Directionality of Crosses

On 5 September 1999 a juvenile sea turtle (BLA-428) was captured near Bahía de los Angeles, Gulf of California, Mexico. The presence of intermediate morphological characteristics suggested this turtle was a hybrid between a green turtle (Chelonia mydas) and hawksbill turtle (Eretmochelys imbricata). BLA-428 exhibited intermediate morphology with respect to number of post-orbital scales, number of prefrontal scales, presence of a median ridge on the lower mandible, carapace scute imbrication, marginal scute dentation, and number of claws on the front flippers. To determine the genotype of BLA-428, we amplified a single-copy nuclear locus CM-14A known to contain species-specific restriction site polymorphisms. Restriction enzyme digests (Dra I and Nde I) of the CM14A fragment indicated this individual was a cross between C. mydas and either E. imbricata or Caretta caretta. Sequence of the mitochondrial DNA control region indicated the mother was E. imbricata with a common Pacific haplotype. This is the first known case of a C. mydas × E. imbricata cross in the Pacific Ocean Basin. Further, it provides the first clear evidence for bi-directional hybridization in marine turtles.