Latest news Developmental patterns of the hermaphroditic gonad in dicyemid mesozoans (Phylum Dicyemida)
Hidetaka Furuya and Kazuhiko Tsuneki
Abstract- The development of the hermaphroditic gonad, the infusorigen, was studied in 16 species belonging to four genera (Conocyema, Dicyema, Dicyemennea, and Pseudicyema) of dicyemid mesozoans. In addition, literature on the cell lineages of infusorigens of eight other species was reviewed. After an agamete (axoblast) undergoes an unequal first division, excluding a small cell (the paranucleus), the resulting large cell divides to form the infusorigen. Five infursorigen cell lineage patterns can be identified: type I, both the first oogonium and the first spermatogonium are produced at the third division; type II, the first spermatogonium is produced at the second division and the first oogonium is produced at the third division; type III, the first spermatogonium is produced at the second division and the first oogonium is produced at the fourth division; type IV, the first oogonium is produced at the second division and the first spermatogonium is produced at the third division; type V, the first oogonium is produced at the second division and the first spermatogonium is produced at the fourth division. Later development is similar in members of all genera. Mature infusorigens are similarly organized in all species examined. Sizes of agametes and infusorigen axial cells, the number of infusorigens, and the type of reproductive strategy were not correlated with infusorigen developmental patterns or cell lineage patterns.
Invertebrate Biology (in press)
Redescription of two Dicyemennea (Phylum: Dicyemida) from Rossia Pacifica (Mollusca: Cephalopoda: Decapoda)
Hidetaka Furuya
Abstract- Two species of dicyemid mesozoan are redescribed from Rossia pacifica Berry, 1911, collected off Iwase in Toyama Bay, Honshu, Japan. Dicyemennea brevicephaloides Bogolepova-Dobrokhotva, 1962, is a large species that reaches about 4,000 žm in length. This species attaches to the surface of the branchial heart appendages. The vermiform stages are characterized as having 23 peripheral cells, a disc-shaped calotte, and an axial cell that extends to the propolar cells. An anterior abortive axial cell is absent in vermiform embryos. Infusoriform embryos consist of 35 cells; a single nucleus is present in each urn cell and the refringent bodies are absent. Dicyemennea rossiae Bogolepova-Dobrokhotva, 1962, is a medium species that reaches about 2,000 žm in length. This species lives in folds of the renal appendages.
Journal of Parasitology (in press)