The Fine Structure of Conidophrys pitelkae Bradbury Related to its Life Cycle and Taxonomic Position in the Apostomatida1

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Abstract
Electron microscopy of the tomite of Conidophrys pitelkae confirms that Jankowski was correct in including the pilisuctorians in the Apostomatida. Like other apostome tomites, the tomite of Conidophrys possesses a rosette opening to the exterior, kinetodesmata made up of stacks of individual kinetodesmal fibrils, and canaliculi that are surrounded by dense inclusion bodies and open on the ventral surface. The fine structure of the trophont of Conidophrys, however, is quite unlike that of other apostome trophonts. The elaborate infraciliature of the tomite disappears immediately after it settles and reappears de novo on the trophont just before tomitogenesis. The cyst wall, which completely encloses the trophont and grows with it, attaches the ciliate to a seta on its, host, the shrimp Crangon crangon. The setae on which tomites settle vary greatly in size and shape, but each appears to have at its tip some digitiform cuticular projections that surmount a pore, which opens into the lumen of the seta. The trophont's only direct connection to its host is at the cytostome, a unique structure formed of delicate tubules that pass through the pore into the lumen of the seta. Ingestion is by micropinocytosis, and there are no visible food reserves.