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The World of Protozoa, Rotifera, Nematoda and Oligochaeta

Ref ID : 4290

Jose F. Fahrni; [Morphologie et Ultrastructure de Spirochona gemmipara Stein, 1852 (Ciliophora, Chonotrichida). III. Appareil de Fixation chez la Larve et chez l'Adulte]. J.Protozool. 31(2):221-232, 1984

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The holdfast apparatus fills the posterior half of the larva; it is comprised of cytoplasmic granules called heterosomes and of about twenty collecting canals which converge at a septate chamber, the rosette. The latter opens to the exterior by a secretory appendage called the podite. My hypothesis is that, when the larva attaches to a substrate, the heterosomal contents empty into the collecting canals and are mixed in the rosette. With the aid of the podite, this secretion is applied to the gill substrate where it forms the so-called style of the future adult. The holdfast apparatus of the adult Spirochona comprises two regions of different nature: the pseudostyle, which is the posterior part of the cell, and the style which is an extracellular secretion. The style looks like a truncated cone and adheres firmly to the substrate. The upper face of the style shows 16-18 stylonemes which are inserted in the crypts of the pseudostylar rosette. The latter corresponds to the larval rosette, and the cryptos communicate with a chamber and numerous suprastylar acini, which represent the remnants of the larval collecting canals. Except for a few details, the holdfast apparatus appears to be similar among all the chonotrichs studied to date. This apparatus differs from that of the Suctoria and of the Peritricha. It has some analogies with the "mouth-rosette" complex of the Apostomatida. Finally, the presence of a podite in a chonotrich larva is new evidence supporting a closer systematic relationship between the Chonotrichida and the Dysteriidae.