Fine structure of dicyemid mesozoans, with special reference to cell junctions.

The fine structure of the dicyemid mesozoan, Dicyema acuticephalum, from Octopus vulgaris, was studied with special attention to intercellular junctional complexes between various kinds of cells. Two types of intercellular junction, namely, adherens junctions and gap junctions, were found in both vermiform stages and in infusoriform embryos. Adherens junctions were classified into two types.

The cell lineages of two types of embryo and a hermaphroditic gonad in dicyemid mesozoans.

The present review summarizes the patterns of cell division and the cell lineages of the two types of embryo, namely, the vermiform embryo and infusoriform embryo, of the dicyemid mesozoan Dicyema japonicum. The infusoriform embryo develops from a fertilized egg. The early cleavages are holoblastic and spiral.