Distribution and attachment of Trypanosoma (Nannomonas) congolense in the proximal part of the proboscis of Glossina morsitans morsitans.

The distribution and attachment of Trypanosoma congolense were investigated in the proximal part of the proboscis of Glossina m. morsitans. In the food canal, epimastigotes and trypomastigotes formed tufts or compact layers. Trypanosomes were attached to the cuticle by their flagella, which formed zonar hemidesmosomes. The flagella were mostly attached parallel to the axis of the labrum and often pointed to its tip. Foot-like processes of the flagella came into contact with adjacent flagella leading to dense grouping of the trypanosomes. Despite narrow contacts between adjacent flagella, no desmosomes were differentiated. The trypanosomes were attached to all parts of the LCI sensilla and might thus impair their function. Uncoated and coated forms were present in the labrum, which indicated that transformation to metacyclic forms is not strictly limited to the hypopharynx. Uncoated forms were often attached to the cuticle of the common salivary duct and hypopharynx by hemidesmosomes. Coated forms could also be attached. Neither compact layers nor tufts of trypanosomes were found. This attachment may partly explain the low number of metacyclics deposited when flies probed on a warm glass slide.