Gregarinasina

The gregarines are a group of Apicomplexan protozoa, classified as the Gregarinasina or Gregarinea.

The gregarines are able to move and change direction along a surface through gliding motility without the use of cilia, flagella, or lamellipodia [Walker et al., 1979]. This is accomplished through the use of an actin and myosin complex [Heintzelman, 2004]. The complexes require an actin cytoskeleton to perform their gliding motions [Mitchison and Cramer, 1996]. In the proposed ‘capping’ model, an uncharacterized protein complex moves rearward, moving the parasites forward [Sibley et al., 1998].

The large (roughly half a millimeter) parasites inhabit the intestines of a large number of invertebrates. They are not found in humans. However, Gregarinasina is closely related to both Toxoplasma and Plasmodium, which cause toxoplasmosis and malaria, respectively. Both protists use protein complexes similar to those that are formed by the gregarines for gliding motility and to invade target cells [Sibley et al., 1998; Menard, 2001; Meissner et al, 2002]. This makes them an excellent model for studying gliding motility with the goal of creating toxoplasmosis and malaria treatment options.