Ultrastructure and host–parasite association of Blastocrithidia gerridis in the ventriculus of Gerris odontogaster (Gerridae: Hemiptera)

Abstract

Blastocrithidia gerridis the type species of the genus Blastocrithidia is parasitic in the gut of bugs of the genus Gerris. The ultrastructure and host–parasite relationship of the epimastigote stages of B. gerridis in the ventriculus of Gerris odontogaster are described. The ultrastructure is typical of other kinetoplastid flagellates but the elongated epimastigotes in the lumen of the ventriculus possess armlike protrusions of the plasma membrane. Intense infections are found in the ventriculus and masses of parallel orientated flagellates are attached to each other by their flagella and to the ventriculus epithelium by interdigitation with microvilli. Parasites and flagella are also wedged in folds of epithelium. Where the epithelium has lost microvilli junctional complexes between flagella and epithelial cell plasma membranes occur but no junctional complexes are observed between flagella and microvilli. A comparison is made between these mechanisms and those described previously for other trypanosomatid–insect or leech associations. The possibility of mixed infections of kinetoplastid flagellates in Gerris is discussed which reinforces the need for a study of the origin or source of promastigote and amastigote organisms found in Gerris species.