Description of Echinobothrium typus van Beneden, 1849 (Platyhelminthes: Diphyllidea) from Raja clavata Linnaeus, 1758 (Pisces: Rajidae) in the Black Sea

Mature specimens of the cestode Echinobothrium typus van Beneden, 1849 from the thornback ray Raja clavata Linnaeus, 1758 that inhabit the Black Sea are found and described in detail for the first time. New details of the scolex armature and reproductive system structures of E. typus are revealed. Infection indices of this cestode in the thornback rays are analyzed. It is shown that the occurrence of E. typus in the definitive host Raja clavata depends not only on the presence and the population density of the intermediate host, presumably, amphipods Perioculodes longimanus Bate et Westwood, 1868, but also on the age-related changes in the food spectrum of the thornback rays.