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Scientific Name Monocystis agilis
Comments An illustration of the Monocystis life cycle. The infection starts with the earthworm ingesting an oocyst (1, 2) that releases sporozoites (3, 4) within the intestines (green). The sporozoite is motile and penetrates the intestinal wall (5) and enters the dorsal blood vessel (6). The sporozoite enters the seminal vesicles (yellow) via the (dark red) dorsoventral hearts (7). The sporozoites feed on the developing spermatocytes (8) in the wall of the seminal vesicle. The gregarines then move into the lumen of the vesicle where they mature into trophozoites. Each ball of sperm within the seminal vesicle contains a young trophozoite (9). These trophozoites are covered by remnants of the sperm cells and often superficially take on the appearance of a ciliated eukaryotic cell. After consuming the sperm ball, the now mature trophozoites pair up in syzygy (10). The trophozoites develop into gamonts, and a gametocyst wall forms around each pair (11). Each of the two gamonts undergoes multiple nuclear divisions to produce many nuclei developing into gametes. Two gametes each fuse and form zygotes, which are surrounded by oocyst walls (12). Within this oocyst, the diploid zygote undergoes meiosis and then mitosis to produce eight haploid daughter cells by a process known as sporogony. The gametocysts, or oocysts if they have been released, leave the earthworm through the male genital pore and are liberated into the soil (13, 14). Infection of a new host occurs by oral ingestion of an oocyst (or perhaps through the process of mutual cross fertilization during host sexual reproduction).
Reference modified after Olsen, O.W. 1974. Animal parasites: Their life cycles and ecology. Dover Publications, Inc., New York.
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Image Use restricted
Attached to Group Monocystids (Gregarina): view page image collection
Title monocystis_lifecycle_newcopy.jpg
Image Type Drawing/Painting
ID 30874
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