Eleven New Species of Dicyemids (Phylum Dicyemida) from Octopus longispadiceus and O. tenuicirrus (Mollusca: Cephalopoda: Octopoda) in Japanese Waters
2018 Volume 23 Issue 2 Pages 143-179
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2018 Volume 23 Issue 2 Pages 143-179
Eleven new species of dicyemid mesozoans are described from two species of octopuses (Mollusca: Cephalopoda: Octopoda): Dicyema cryptocephalum sp. nov., Dicyema petalocephalum sp. nov., Dicyemennea acetabulum sp. nov., Dicyemennea anteronucleatum sp. nov., Dicyemennea mcconnaugheyi sp. nov., Dicyemennea megalosomum sp. nov., and Dicyemennea leptocephalum sp. nov. from Octopus longispadiceus (Sasaki, 1917) (Octopoda: Octopodidae) collected in the Sea of Japan, Honshu, Japan and four species, Dicyemennea desmocephalum sp. nov., Dicyemennea moritakii sp. nov., Dicyemennea tobaense sp. nov., and Dicyemodeca kukii sp. nov. from O. tenuicirrus (Sasaki, 1929) (Octopoda: Octopodidae) collected in the Kumano-nada Sea, off the Kii Peninsula, Pacific coast of Honshu, Japan. Dicyemnnea megalosomum sp. nov., at length 15,200 µm, is the largest of these newly described species. Dicyemennea moritakii sp. nov. has 47 peripheral cells that is shown in the most of all the described species. Some species demonstrate morphological characters in the calotte (anterior part) of their adult stage: thin and irregular in Dicyemennea leptocephalum sp. nov.; disc- or wheel-like in Dicyemennea acetabulum sp. nov., Dicyemennea desmocephalum sp. nov., Dicyemennea megalosomum sp. nov., and Dicyemennea moritakii sp. nov.; cap-shaped in Dicyemodeca kukii sp. nov.; conical in D. anteronucleatum sp. nov., Dicyemennea mcconnaugheyi sp. nov., and Dicyemennea tobaense sp. nov.; and with petal-like parapolar projections in Dicyema cryptocephalum sp. nov. and Dicyema petalocephalum sp. nov. Species Dicyemennea desmocephalum sp. nov. and Dicyemennea leptocephalum sp. nov. have an unusual property in which individuals adhere to each other at the periphery of their calotte. The co-occurrence patterns of dicyemid species with distinct morphological characters are briefly discussed in relation to adaptations to the renal habitat.
