New records of the chaetiferous leech-like annelid Paracanthobdella livanowi (Epshtein, 1966) (Annelida: Clitellata: Acanthobdellida) from Kamchatka, Russia

摘要

Acanthobdellidans are unique in their organisation and phylogenetic relationships due to having transitional characters that combine features of oligochaetous and achaetous annelids. Alongside the relatively well-studied Acanthobdella peledina Grube, 1851, there is another member of the group, Paracanthobdella livanowi (Epshtein, 1966), with five rows of chaetae and an anterior sucker. It appears that the anterior sucker is weakly developed in small juveniles but acquires a deep cavity in adults. Smaller individuals of P. livanowi can be distinguished from A. peledina, which does not possess an anterior sucker, by the varying breadth of their chaetae. The mid-body segment consists of two doubled annuli in juveniles and is quadri-annulate in large individuals. In Kamchatka freshwaters, hosts of P. livanowi mostly include Salvelinus spp. and more rarely Gasterosteus aculeatus, Oncorhynchus mykiss and O. kisutch. New information on the distribution and the biology of P. livanowi is presented.