Toward a taxonomic revision of the medicinal leech Hirudo medicinalis Linnaeus, 1758 (Hirudinea: Hirudinidae): re-description of Hirudo troctina Johnson, 1816 from North Africa

The medicinal leech Hirudo medicinalis Linnaeus, 1758 is genotype of the genus Hirudo and constitutes the taxonomic basis for the family Hirudinidae and even the class Hirudinea. In spite of its unique taxonomic significance, H. medicinalis has never been characterized in terms of criteria currently accepted for the Hirudinea. As part of a broader revision of this species, Hirudo troctina Johnson, 1816 from North Africa is re-described based on the foregut and internal diagnostic characters. The authors confirm that H. troctina is a separate species from H. medicinalis as currently understood. In addition to external differences (four or six metameric dorsal black dots in H. troctina), the male and female reproductive anatomy consistently distinguish H. troctina (vagina bulbous, upright and not folded; epididymis massive in relation to ejaculatory bulb) from H. medicinalis (vagina a folded, elongated tube in non-juveniles; epididymis not much larger than ejaculatory bulb). Furthermore, several possible errors in the description of taxonomic features of the foregut of H. medicinalis (e.g. claimed absence of a sulcus and salivary papillae) appear to have been perpetuated in the literature, requiring a re-evaluation of the genus Hirudo.