Morphological and molecular identification of Mustelus mustelus and Mustelus punctulatus

Mustelus is the most species-rich genus of the widespread family Triakidae and represents a significant fraction of the elasmobranch catch in the northern Adriatic Sea where the common (M. mustelus) and blackspotted (M. punctulatus) smooth-hound co-occur. The two species share several morphological and morphometric characters that often lead to uncertainty in the identification and frequent misidentification. In order to provide information useful for their recognition, we performed a morphological and molecular identification of the two species based on seven morphological characters, namely presence/absence of black stripe on the 1st and 2nd dorsal and caudal fins, edge shape of the 1st and 2nd dorsal fins, presence/absence of small black spots on sides, ratio inter-nostril distance/nostril length; and three molecular tests, that is a DNA barcoding analysis based on amplification of the cytochrome oxidase subunit 1 (COI), a fragment analysis based on hypervariable nuclear markers (microsatellites) and a hybridization assay based on the nuclear codominant marker ITS2. Preliminary results show that some individuals present ambiguous identification characters. Moreover, molecular tests suggest the occurrence of some degree of reproductive interactions between the two species