On the occurrence of the Dragon leech Hirudo troctina Johnson, 1816 (Annelida, Hirudinea) in Sardinia (Italy)

Abstract

In recent decades, medicinal leeches of the genus Hirudo have experienced a sharp decline throughout their distribution range due to their overexploitation for medical use and habitat alteration. Such a phenomenon is not fully understood because of the complex taxonomy of the genus, which remained unsettled until the beginning of the XXI century, when the implementation of DNA taxonomy allowed for a better understanding of the diversity of the genus and the distribution ranges of Hirudo species. Only the Mediterranean medicinal leech Hirudo verbana Carena, 1820 is currently reported to occur in Italy and its major islands, although records of other Hirudo species have been reported in the literature. In this study, we report the occurrence of the Dragon leech Hirudo troctina Johnson, 1816 in Sardinia and provide its molecular characterization. In addition, based on a review of the existing literature and museum collections, we provide an ample synopsis of the available evidence regarding the occurrence of the species on the island. Hirudo troctina proved to be widespread and abundant in Sardinia during the XIX century but became rarer and rarer in the XX and XXI centuries possibly due to its overexploitation for medicinal use and export in mainland Europe, the abandonment of traditional grazing practices, and the decline of wetland habitats and amphibian populations. Currently, the only recently validated occurrence sites of the species are the water bodies of the "Giara di Gesturi", a basaltic plateau in central-southern Sardinia. No corroborated evidence of the possible occurrence of other Hirudo species on the island was found. A better understanding of Hirudo troctina distribution in Sardinia will allow the amelioration of its protection and management practices, also under the provisions of the European "Habitats Directive", where the H. medicinalis species complex is listed in Annex V.