The cell coat of Crithidia fasciculata.

A prominent filamentous and granular cell coat is associated with the plasma membrane of haptomonads of Crithidia fasciculata attached to the cuticular lining of the hindgut of Anopheles gambiae. This surface material is completely absent from morphologically identical haptomonads from the mosquito foregut and from rosettes in culture. On the basis of these observations, it is suggested that cell coat formation is dependent on suitable environmental conditions. A cytochemical staining technique indicates the presence of carbohydrates in (a) the cell coat, (b) the outer leaflet of the plasma membrane of haptomonads from all locations and (c) small cytoplasmic vesicles and multivesicular bodies in all haptomonads. It is suggested that these cytoplasmic organelles represent stages in the intracellular pathway for material ingested by pinocytosis rather than elements involved in surface coat formation.