Echinobothrium chisholmae n. sp (Cestoda, Diphyllidea) from the giant shovel-nose ray Rhinobatos typus from Australia, with observations on the ultrastructure of its scolex musculature and peduncular spines

Echinobothrium chisholmae n. sp. is described from Rhinobatos typus Bennett (Rhinobatidae), collected from Heron Island, Great Barrier Reef, Australia . E. chisholmae differs from all congeners in possessing 11 hooks in each d orsal and ventral group on the rostellum and groups of 3-6 hooklets on eith er side of the hooks. A single metacestode of E. chisholmae was collected f rom the decapod crustacean Penaeus longistylus Kubo. Yellow pigmentation of the cephalic peduncle in immature adults is caused by the accumulation of large vesicles in the distal cytoplasm of the tegument. The vesicles probab ly provide materials for spine formation. Ultrastructural examination of th e rostellar musculature revealed that the muscles are stratified (striated- like), consisting of a periodic repetition of sarcomeres separated by perfo rated Z-like lines that are oblique to the long axes of the myofilaments.