A taxonomic revision of Octomacrum Mueller, 1934 (Monogenea: Polyopisthocotylea: Octomacridae), including an 18S DNA based phylogeny

Abstract

The genus of fish parasite, Octomacrum, consists of six species that parasitize certain catostomids and cyprinids in North America and Europe. Little is known about these parasites, and the original descriptions lack detail and standardization of descriptive terminology. The present study undertakes a taxonomic revision of the genus, using new material when available and extensive museum collections of all six species in the genus: O. lanceatum, O. microconfibula, O. semotili, O. spinum, O. mexicanum and O. europaeum. A dichotomous key to all six species using features of the attachment clamps with new figures is provided. A molecular phylogeny based on 18S DNA provides enough variation to infer relationships between 2 members of the genus, while grouping the remaining four into an unresolved clade. This study concludes that in spite of poor descriptions for many of the species, the taxonomy of this group has remained stable with few misidentifications.