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.

Host—parasite relationships ofBlastocrithidia familiarisinLygaeus pandurusScop. (Hemiptera: Lygaeidae)

“…Hemidesmosome formation is the usual method of attachment to cuticular surfaces of the foregut and hindgut of insects (Molyneux, 1977(Molyneux, , 1983. However, there are several descriptions of trypanosomatids with the formation of a junctional complex between flagella and epithelial membranes; these include T. brucei attached to the salivary gland of microvilli of a tsetse vector (Steiger, 1973;Tetley & Vickerman, 1985), T. rotatorium attached to the gastric epithelium of the leech Batracobdella picta (Desser, 1976), and B. gerridis attached to epithelial cell membrane of the midgut of Gerris odontogaster (Tieszen et al 1983). It is of interest to note that in two of these examples, T. rotatorium and B. gerridis, host cell microvilli were observed to be reduced in the regions of attachment.…”

“…In contrast to flagellate attachment to rectal glands or pads alone, Crithidia fasciculata attaches to all parts of the rectum in Anopheles gambiae (Brooker, 1971), although Brooker induced his infections in A. gambiae with C. fasciculata which had been maintained in culture for many years after its isolation from mosquitoes. Tieszen et al (1983) described a mode of attachment for B. gerridis in which the close association between flagella and the corrugated surfaces of the cell bodies of free epimastigotes which lie parallel to each other assists in the maintenance of the parasites in the ventricular lumen of Gerris. A similar type of parasite-parasite attachment, though less extensive, occurs with B. familiaris in the midgut lumen of L. pandurus.…”

“…This paper is the first ultrastructural description of attachment by intraflagellar expansion without the formation of hemidesmosomes in a Blastocrithidia species and the first description of this type of attachment to insect midgut microvilli for the Trypanosomatidae. Trypanosomatids which attach to insect microvilli by interdigitation but without expanded flagella have been reported (Killick-Kendrick, Molyneux & Ashford, 1974;Molyneux, 1975;Rowton et al 1981;Tieszen et al 1983).…”

“…Mehlhorn, Schaub, Peters & Haberkorn (1979) described B. triatomae in Tri. infestans and Tieszen, Heywood & Molyneux (1983) described the host-parasite relationships of B. gerridis in the ventriculus of Gerris odontogaster.…”

Scanning Electron Microscopic Studies of Blastocrithidia triatomae (Trypanosomatidae) in the Rectum of Triatoma infestans (Reduviidae)12

“…Apart from the importance for the competition theory, this investigation was also performed because SEM of the genus Blasfocrithidia has only been published for B. gerridis (23) and is totally lacking for trypanosomatids developing flagellar cysts ("straphangers").…”