Monocystisis a parasite of invertebrates and is referred to as the earthworm parasite, because it is a parasite that is commonly found in earthworms. Monocystis is a gregarine in the phylum apicomplexa.
Monocystis is directly transmitted to other earthworms via other earthworms (STI, dead worms, feces in the soils, soil via bird). The parasite travels to the seminal vesicle of the worm and develops into the trophozoite stage (feeding stage). The tropozoite proceeds to feed on the sperm of the worm, which reduces the reproductive fitness of the worm. Two trophozoites then fuse to create a gametocyst, which is a cyst formed around a pair of gamonts in which gametes are produced after multiple cell divisions. Two gametes then fuse and meiosis occurs. Each cell develops into a sporocyst, which is a cell sac that contains spores in which sporozoites are then created. A typical Monocystis sporocyst will divide to create 8 sporozoites per sporocyst.