THE SYNONYMY OF PROTEOCEPHALUS-NEGLECTUS LARUE, 1911 WITH P-EXIGUUS LARUE, 1911, 2 FISH CESTODES FROM THE HOLARCTIC REGION

Two cestode species of the genus Proteocephalus Weinland, 1858, P. neg lectus La Rue, 1911, parasitic in salmonid fishes, and P. exiguus La R ue, 1911, occurring mostly in coregonids, were evaluated taxonomically . Comparison of the morphology and morphometry revealed that the taxa apparently represent morphological forms of one polymorphic species, f or which the name Proteocephalus exiguus La Rue, 1911 is proposed. A r edescription of this species, based on extensive comparative material from different fish hosts and geographical areas, is given. The reliab ility of criteria (size of the body and shape of segments, characteris tics relating to the head morphology, presence/absence of microtriches on the scolex surface, relative size of the cirrus-sac, number of tes tes and testicular layers, shape of genital atrium, size of the egg) u sed previously for differentiating these species is also discussed.