DITRYPANOCYSTIS SP. (APICOMPLEXA, GREGARINIA, SELENIDIIDAE): THE MODE OF SURVIVAL IN THE GUT OF
ENCHYTRAEUS ALBIDUS (ANNELIDA, OLIGOCHAETA, ENCHYTRAEIDAE) IS CLOSE TO THAT OF THE COCCIDIAN GENUS
CRYPTOSPORIDIUM *
F. Butaeva,1 G. Paskerova,1 R. Entzeroth 2
1 Department of Invertebrate Zoology, Faculty of Biology and Soil, St. Petersburg University,
Russia, and 2 Institute of Zoology of Dresden Technical University, Germany;
e-mail: fbutaeva@yahoo.com
A selenid gregarine Ditrypanocystis sp. (Apicomplexa, Gregarinia, Selenidiidae), harboring the gut lumen of
the oligochaete Enchytraeus albidus, was studied by light and electron microscopy. The trophozoite of
Ditrypanocystis sp. is attached to the gut wall with its apical end to be anchored eventually between
enterocytes in the crypts. Simultaneously, between the surfaces of the parasite and the host cell a peculiar contact
is formed made of membranous channels and vesicles of unknown origin, the host cell surface in the contact area
lacking cilia. The trophozoite becomes progressively enclosed within a parasitophorous vacuole made of layers of
fused ciliar membranes of enterocytes. The fused cilia may be a source of membranes lining channels and vesicles of
the contact area. Such a mode of parasitophorous arrangements has never been described before for gregarines,
however, it bears a some likeness with that of the coccidian genus Cryptosporidium (similarity and differences
being discussed). With regard to some molecular phylogeny constructions, claiming the "sister" relationship between
gregarines and the coccidian genus Cryptosporidium (Carreno et al., 1999; Leander et al., 2003), this common
feature in host-parasite relationships enabled us to put forward an idea of a possible evolutionary route from
extracellularity of gregarines to intracellularity of coccidia, as exemplified by species of Cryptosporidium.
Key words: gregarine, Ditrypanocystis, Selenidiidae, ultrastructure, phylogeny,
Cryptosporidium
* Paper in English.
Back
Contents
Main
|
