A new species of Bothriocephalus Rudolphi, 1808 (Eucestoda: Bothriocephalidea) from the channel bull blenny Cottoperca gobio (Günther) (Perciformes: Bovichtidae) on the Patagonian shelf off Argentina.

Bothriocephalus timii n. sp. is the first tapeworm species reported from a bovichtid fish. The new species was commonly found (prevalence 85%) in the intestine of Cottoperca gobio (Günther) collected on the Patagonian shelf off Argentina. It is characterised by a strobila with segments and proglottides usually longer than wide, having posterolateral wing-like expansions with a medial notch on both the dorsal and ventral surfaces; a scolex with an apical disk; elongate bothria opening posteriorly, with laterally and longitudinally extended convex lappets; testes 42-185 in number, in one layer, arranged in two lateral continuous bands along the strobila; an elongate cirrus-sac, situated obliquely, with the proximal part curved anteriolaterally; and an ovary which is usually butterfly-shaped. The new species is morphologically similar to B. bengalensis Devi, 1975 from Carangoides plagiotaeniata Bleeker, B. branchiostegi Yamaguti, 1952 from Branchiostegus japonicus Houttuyn, B. carangis Yamaguti, 1968 from C. ferdau Forsskål and B. gadellus Blend & Dronen, 2003 from Gadella imberbis (Vaillant) based on the presence of posterolateral wing-like expansions with a medial notch on dorsal and ventral surfaces of segments and proglottides along the strobila. Bothriocephalus timii n. sp. differs from B. bengalensis, B. branchiostegi and B. carangis in the absence of a vaginal sphincter and from B. gadellus in the number of testes and the size of scolex. Unpublished molecular data suggest that B. timii is most closely related to B. australis Kuchta, Scholz & Justine, 2009 from Platycephalus spp. and B. scorpii (Müller, 1776) from Myoxocephalus scorpius (Linnaeus). The genus Indobothrium Sedova & Gulyaev, 2009 is herein considered a junior synonym of Bothriocephalus Rudolphi, 1808.