Two New Species of Dicyema (Dicyemida: Dicyemidae) from Amphioctopus areolatus (Mollusca: Cephalopoda: Octopodidae)

Two new species of dicyemid mesozoan are described from Amphioctopus areolatus (de Haan, 1840) collected off Irino in Tosa Bay, southern Shikoku, and off Akashi in Osaka Bay, Honshu, Japan. Dicyema balanocephalum sp. nov. is a species of medium size that reaches about 1500μm in length. The vermiform stages are characterized by 19-21 peripheral cells, an elongate calotte, and an axial cell that extends to the base of the propolar cells. Infusoriform embryos consist of 37 cells; two nuclei are present in each urn cell, and the refringent bodies are solid. Dicyema leiocephalum sp. nov. is a species of medium size that reaches about 2000μm in length. The vermiform stages are characterized by 22 peripheral cells, a conical, smooth-surfaced calotte, and an axial cell that extends to the base of the propolar cells. Infusoriform embryos consist of 37 cells; two nuclei are present in each urn cell, and the refringent bodies are solid. This is the first report of dicyemids in A. areolatus.