Historical survey of artefacts in Mediterranean museum collections of small Delphinidae

In recent decades, a decline in the populations of Delphinus delphis, Stenella coeruleoalba and Tursiops truncatus has been observed in the Mediterranean Sea, leading to the implementation of conservation measures. In order to best determine the status of these species, historical populations need to be reconstructed to provide data for a better understanding of population trends and the implementation of management plans. In the present study, museum specimens of the species were examined in Italian museums. Combined morphometric and molecular analyses were performed to accurately identify museum specimens. 23 museums were identified where the exhibits of interest were present. A total of 164 images of dolphin skulls were collected and analysed using morphometric approaches and point-based cranial analysis to taxonomically distinguish among the three species. In addition, 280 bone tissue samples were collected, of which 18 were processed by molecular analysis using the cytochrome B. Sequences were compared with referenced sequences available in the public databases and a phylogenetic analysis was carried out for taxonomic purposes including 30 referenced sequences for each species and 12 sequences obtained from historical specimens. Among the main findings, previously unidentified museum specimens were identified and morphometric analyses revealed specimens that could be potential hybrids. Cranial differences between the three species were confirmed, and cases of misidentification were found in comparison with those reported in the bibliography. On the basis of the results obtained, it is suggested that further investigations be carried out on the museum specimens with more in-depth molecular analyses, supported by morphometric analyses, in order to reclassify the specimens, increasing their scientific value, and to provide information to obtain a representative estimate of the historical populations of D. delphis, S. coeruleoalba and T. truncatus in Italian seas.