Morphological and molecular identifications of sea turtles Lepidochelys olivacea and Eretmochelys imbricata from the Turtle Bay of Cilacap, Indonesia

Abstract

DNA barcoding is a powerful tool for accurately identifying marine turtle species, especially when morphological identification is challenging, owing to insufficient clues in the samples available. This study focused on two sea turtle samples of dead adults washed ashore and babies hatching out from nests, which pose a challenge for morphological identification. They represented two species, the Olive Ridley Turtle Lepidochelys olivacea and Hawksbill Turtle Eretmochelys imbricata, from Turtle Bay, Cilacap, Indonesia. For one sample, morphological identification initially suggested it as a Green Sea Turtle Chelonia mydas, based on traits like a pair of prefrontal scales, brown carapace colouration, and the absence of serrations on the posterior carapace. The degraded condition of the specimen and shared juvenile traits between C. mydas and E. imbricata made conclusive identification challenging. Using mtDNA barcoding with the CO1 gene provided more accurate species identification, revealing the sample to be E. imbricata with a perfect genetic match in the BLAST search (0% divergence). This result highlights the advantages of molecular approaches when traditional methods fall short. Phylogenetic analysis of L. olivacea and E. imbricata sequences revealed close clustering of sampled sequences with published sequences from Ghana, Australia, and China. High bootstrap values of 92% for L. olivacea and 98% for E. imbricata confirmed the molecular identifications of these samples. The study underscores the value of combining DNA barcoding and phylogenetics for marine turtle identification and evolutionary insights, with implications for conservation and species management.