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Summary Protoopalina drachi Tuzet & Knoepfler 1968 found in the african frog Ptychadena maccarthensis presents general ultrastructural features of Opalinids: cortical folds substained by longitudinal microtubules associated by bouble strands and inserted between antero-posterior growing kineties; a cortical zone with numerous pinocytic vesicles, removal vesicles and Golgi bodies: mitochondria with tubular cristae and dense matrix: falcular and somatic kinetosomes differentiated by particular appendages: a double transitional helix in all the flagella; a paraxonemal fibre in the falcular flagella; nuclei dividing by cryptomitosis. As we have already shown in P. saturnalis, P. drachi contains in the anterior part of the cell a large microfibrillar band, associated with the falcular kinetosomes and which acts as a MTOC for the cortical microtubules. Like in the other protoopalinids studied by electron microscopy, exocytic and endocytic vesicles are mixed. Our observations show new characters, for example granular fibres associated with the triplets in the lumen of all the kinetosomes. This character seems to be specific of Protoopalina. A fibrillar layer envelops the cytoplasmic face of the nucleus during all the cell cycle. The choise of a new fixation for a better preservation of the cytoskeletal structures explains perhaps this observation and we don't known if it is the same in the other Protoopalinids, but we have it never seen in Opalina prepared with the same fixative. It may be a structure specific of species possessing one or two nuclei, probably the primitive forms. |
