Question

Monocystis belongs to the order of
A. Gregarinida
B. Coccidia
C. Microsporidia
D. Sarcosporidia

Answer 1

Hint: Monocystis lives in the bundle of developing sperms in the young stage. In its mature stage, it becomes extracellular when it lives in the contents of seminal vesicles of earthworms. The adult mature Monocystis is called a trophozoite.

Complete answer:
The mode of reproduction in Monocystis is sexual and is always followed by asexual reproduction. Both processes are interdependent.
The gregarines are a group of Apicomplexan alveolates. They are classified as the Gregarinasina or Gregarinia. The large parasites inhabit the intestines of many invertebrates and are not found in any vertebrates.
Monocystis is an endoparasite, which is found in the seminal vesicle and coelom of earthworms. It belongs to the order of Gregarinida. Its life cycle is completed in a single host that is the earthworm, it is a monogenetic parasite.
Coccidia is a subclass of spore-forming parasites. These are single-celled obligate intracellular parasites belonging to the class Conoidasida. These are microscopic. As they are obligate intracellular parasites, they must live and reproduce within an animal cell.
Microsporidian, any parasitic fungus of the phylum Microsporidia. It is found mainly in cells of the gut epithelium of insects and the skin and muscles of fish. They also occur in some annelids and some other invertebrates.
Sarcosporidia is an order of Coccidia. The lifecycle of a member of the genus, Sarcocystis, involves two host species, a definitive host and an intermediate host.

Hence, the correct answer is option (A).

Note: Monocystis, it lives as an intracellular parasite as well as an extracellular parasite. Monocystis which belongs to the order of Gregarinida is found in the seminal vesicle and coelom of earthworms. Monocystis is defined as a monogenetic parasite. It means its life cycle is completed in a single host that is the earthworm.