A study of the ultrastructure and gliding movement of Gregarina garnhami (eugregarina, protozoa).

Gregarlna garnhaml is a gut parasite of the desert locust Schistocerca gregaria G. garnhami exhibits an unexplained gliding movement. Gliding movement is accompanied by the formation of a mucus trail. Light microscope observations reveal that G. garnhami requires a substrate on which to glide, it can change direction whilst gliding but cannot glide backwards. Ultrastructural observations show that the surface of the cell is thrown into longitudinal epicyte folds, bounded by a triple membrane complex or pellicle. At the tip of each fold are a series of 7 nm diameter electron dense and 15 nm diameter less electron dense longitudinally orientated structures. The cytoplasm is divided into a narrow layer of ectoplasm lying below the folded membrane complex, and a core of granular endoplasm containing paraglycogen, Microtubules are found at the ectoplasm/endoplasm border. Antiactin immunofluorescent staining and electrophoresis were employed to investigate the presence of actin in G. garnhami. Animals were treated with the drugs Cytochalasin B and Colchicine to investigate the possible involvement, in gliding, of actin microfilaments and microtubules respectively. A model for gregarine gliding movement is proposed on the basis of this microscopic and experimental evidence. It is suggested that gregarines glide by vertical undulation of the epicyte folds. Undulation is thought to be caused by interaction of longitudinal filaments in the epicyte folds corresponding to the 7 nm dense structures, with, the membrane complex and the 15 nm structures. Also of interest is the presence, in the cytoplasm, of bacteria-like structures. Their ultrastructure is described and compared to that of symbiotic bacteria in other protozoa. Attempts are made to confirm their bacterial nature.