Redescription of the unicorn icefish Channichthys rhinoceratus Richardson (Notothenioidei: Channichthyidae) with synonymization of three similar species

Abstract

On the basis of a comprehensive study of the external morphology, seismosensory system and gill apparatus, a revision of the Kerguelen icefishes of the genus Channichthys Richardson, 1844 (Notothenioidei: Channichthyidae) was carried out in order to confirm or refute the validity of a questionable species of this genus. The need for the presented study arose due to the lack of an unambiguous accepted opinion of various specialists about the exact species composition of this genus of Antarctic fish. The studied sample included 40 specimens of the type species of this genus, unicorn icefish Channichthys rhinoceratus Richardson, 1844 from the collection of the Zoological Institute RAS and holotypes of 3 species, Aelita icefish Ch. aelitae Shandikov, 1995, green icefish Ch. mithridatis Shandikov, 2008 and robust icefish Ch. richardsoni Shandikov, 2011, from the Zoological collection of the National Museum of Natural History NAS of Ukraine. The classical technique was used for the morphological study of fish with subsequent comparative analysis of the data obtained. As a result, Ch. rhinoceratus is redescribed, highlighting the most important diagnostic characters. Three similar species (Ch. aelitae, Ch. mithridatis and Ch. richardsoni) are place in synonymy of the latter. Basing on the results of this and our previous species revisions of Channichthys, a key for identification has been compiled, which includes diagnostic features of all four valid icefishes, Ch. rhinoceratus, Ch. velifer, Ch. rugosus and Ch. panticapaei.