Metacestodes of Elasmobranch Tapeworms in Octopus vulgaris (Mollusca, Cephalopoda) from Central Mediterranean—SEM and Molecular Data

SIMPLE SUMMARY: Information on the role of cephalopods in the life cycle of elasmobranch tapeworms and other parasites transmitted through the food web is limited. Such knowledge is useful to gain further understanding of the biology and ecology of this group of mollusks and would inform a correct management of wild cephalopod stocks for conservation and fishery purposes. In the present work, we aimed to characterize tapeworms infecting the common octopus Octopus vulgaris, one of the most widely distributed and commercially important cephalopod species, with morphological and molecular methods. Our results suggest a possible important role of O. vulgaris in the transmission of elasmobranch tapeworms and add valuable information on the host-range and distribution of the tapeworms identified. ABSTRACT: Cephalopods are intermediate/paratenic hosts in the life cycle of elasmobranch tapeworms, nevertheless most records of infection in this group of mollusks are outdated and fragmentary. The present work aimed to investigate the cestode fauna of the common octopus Octopus vulgaris from the Tyrrhenian Sea (Central Mediterranean). The parasitic stages were characterized by light and Scanning Electron Microscopy (SEM) and sequencing of 28S rDNA. Three cestode taxa were identified to the genus level: the onchoproteocephalidean Acanthobothrium sp. (prevalence 28%), the “tetraphyllidean” Anthobothrium sp. (prevalence 13%) and the trypanorhynch Nybelinia sp. (prevalence 3%). The remarkable prevalence observed for gastrointestinal cestodes highlight a possible important role of O. vulgaris in the transmission of elasmobranch tapeworms, particularly Onchoproteocephalideans. Furthermore, the present work provides, for the first time, detailed morphological (SEM) and molecular support to confirm the occurrence of Anthobothrium sp. in cephalopod hosts. In order to gain higher taxonomic resolution for the identified taxa, we stress the need to collect further morphological and molecular data of adult cestodes infecting their elasmobranch definitive hosts.