''Monocystis (Gr., monos, ''single'' + kystisis, ''bladder'')'' is a genus (the type of the family

Monocystidae The Monocystidae are a family of parasitic alveolates in the phylum Apicomplexa. Taxonomy There are five subfamilies in this family: ''Monocystinae'', ''Oligochaetocystinae'', ''Rhynchocystinae'', ''Stomatophorinae'' and ''Zygocystinae''. Hist ...

) of acephaline gregarines (subclass Gregarinasina) not having the protoplasm divided into segments by septa and including internal parasites of

invertebrates Invertebrates are a paraphyletic group of animals that neither possess nor develop a vertebral column (commonly known as a ''backbone'' or ''spine''), derived from the notochord. This is a grouping including all animals apart from the chordate ...

(as ''M. agilis'' of the reproductive system of

earthworms An earthworm is a terrestrial invertebrate that belongs to the phylum Annelida. They exhibit a tube-within-a-tube body plan; they are externally segmented with corresponding internal segmentation; and they usually have setae on all segments. Th ...

Habit and habitat

Monocystis lives as an intracellular

parasite Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson has ...

in its young stage when it lives in the bundle of developing

sperms Sperm is the male reproductive cell, or gamete, in anisogamous forms of sexual reproduction (forms in which there is a larger, female reproductive cell and a smaller, male one). Animals produce motile sperm with a tail known as a flagellum, whi ...

and becomes extracellular in its mature stage when it lives in the contents of seminal vesicles of earthworms. Its infection is so wide that practically all mature earthworms are found parasitized by this parasite.

Structure

The adult mature of ''Monocystis'' is called

trophozoite A trophozoite (G. ''trope'', nourishment + ''zoon'', animal) is the activated, feeding stage in the life cycle of certain protozoa such as malaria-causing ''Plasmodium falciparum'' and those of the '' Giardia'' group. (The complement of the trophozo ...

which is a feeding stage. The young trophozoite lives in the sperm

morula A morula (Latin, ''morus'': mulberry) is an early-stage embryo consisting of a solid ball of cells called blastomeres, contained in mammals, and other animals within the zona pellucida shell. The blastomeres are the daughter cells of the zygote ...

(sperm morula is a group of developing sperms) of the host; it feeds and grows at the expense of the

protoplasm Protoplasm (; ) is the living part of a cell that is surrounded by a plasma membrane. It is a mixture of small molecules such as ions, monosaccharides, amino acid, and macromolecules such as proteins, polysaccharides, lipids, etc. In some defini ...

of the developing sperms until all the protoplasm is exhausted. So, it is now seen to be surrounded by the tails of the dead sperms. In this stage, it is sometimes mistaken to be a

cilia The cilium, plural cilia (), is a membrane-bound organelle found on most types of eukaryotic cell, and certain microorganisms known as ciliates. Cilia are absent in bacteria and archaea. The cilium has the shape of a slender threadlike projecti ...

ted organism. But, soon the sperm tails are detached from its body and the trophozoite becomes free The adult is elongated, spindle shaped, flattened and worm like creature. Body is covered by thick smooth and permeable pellicle. Cytoplasm is well differentiated in to ectoplasm and endoplasm. endoplasm contains a large vesicular nucleus. It nutrition is sporozoic. there are no locomotory organs but it shows wriggling and gliding movements.

References

{{Taxonbar, from=Q18606206 Conoidasida Apicomplexa genera