Ultrastructure of cyst formation in Blastocrithidia familiaris in Lygaeus pandurus (Hemiptera: Lygaeidae)

The ultrastructural study of encystment of Blastocrithidia familiaris in the host Lygaeus pandurus is described. Cysts were found attached to flagella of epimastigotes and free in the gut lumen. Most mature cysts were observed in the ileum and rectum, but small numbers were also observed in the ventriculus. Encystment in B. familiaris is characterised by condensation of the nuclear chromatin, kinetoplast and cytoplasm. Morphological changes seen in the plasmalemma include the formation of a dense surface coat around the outer membrane and a dense layer around the inner membrane on the side facing the cytoplasm. The subpellicular microtubules are not seen in mature cysts. A comparison is made with recent ultrastructural studies of encystment of Blastocrithidia triatomae in vitro and excystment of B. triatomae in artificially infected hosts. This report is the first known ultrastructural description of encystment in a phytophagous hemipteran and in a naturally infected host.