Identification complexity of critically endangered Squatina squatina (Linnaeus, 1758) and Squatina aculeata Cuvier, 1829 in the Mediterranean Sea (Turkey)

Sharks and rays, besides their economic importance, are ecologically important organisms with a diverse group. After a pregnant Squatina sp. was captured as by-catch, Akyol et al. (2015) published this species as Squatina squatina while the COI and 16S rDNA analysis demonstrated that the species is S. aculeata. This complexity revealed that utilizing morphologic identification solely might not be enough to distinguish these two Squatina species accurately. We aim to compare morphologic and molecular techniques during species identification of critically endangered S. squatina and S. aculeata. Two different gene regions were used for molecular identification of 3 Squatina specimens obtained from the Aegean coasts of Turkey. Sequence analysis of two gene regions was conducted after PCR analysis. An aligned data set was used for creating phylogenetic trees. The results demonstrated that the previously identified S. squatina specimen was revealed as S. aculeata after molecular analysis. Two other specimens which were morphologically identified as S. squatina demonstrated the same results both with molecular and morphological analysis. Our results suggest that adopting morphological identification as the only tool is not enough to accurately determine the Squatina species; both morphological and molecular tools should be used for taxonomical identification of shark species, especially the endangered ones, to assure their conservation status.

Automated summary

Morphological identification alone might not accurately distinguish between the critically endangered S. squatina and S. aculeata species of sharks and rays. This study compared morphological and molecular techniques for species identification, and found that both techniques should be used to ensure accurate taxonomical identification of shark species, especially the endangered ones.