A ''mucron'' is an attachment

organelle In cell biology, an organelle is a specialized subunit, usually within a cell, that has a specific function. The name ''organelle'' comes from the idea that these structures are parts of cells, as organs are to the body, hence ''organelle,'' t ...

found in archigregarines - an order of epicellular parasitic Conoidasida.Simdyanov TG, Guillou L, Diakin AY, Mikhailov KV, Schrével J, Aleoshin VV. (2017) A new view on the morphology and phylogeny of eugregarines suggested by the evidence from the gregarine ''Ancora sagittata'' (Leuckart, 1860) Labbé, 1899 (Apicomplexa: Eugregarinida) PeerJ 5:e3354 https://peerj.com/articles/3354/?td=wk The mucron is derived from the apical complex, which is found in all members of the

phylum In biology, a phylum (; plural: phyla) is a level of classification or taxonomic rank below kingdom and above class. Traditionally, in botany the term division has been used instead of phylum, although the International Code of Nomenclatu ...

Apicomplexa.Adl SM, Simpson AG, Lane CE, Lukeš J, Bass D, Bowser SS, Brown M, Burki F, Dunthorn M, Hampl V, Heiss A, Hoppenrath M, Lara E, leGall L, Lynn DH, McManus H, Mitchell EAD, Mozley-Stanridge SE, Parfrey LW, Pawlowski J, Rueckert S, Shadwick L, Schoch C, Smirnov A, Spiegel FW. (2012) The revised classification of eukaryotes. Journal of Eukaryotic Microbiology 59:429-514. https://doi.org/10.1111/j.1550-7408.2012.00644.x The mucron is located at the anterior (apical) end of the cell and comprises the conoid,

rhoptries A rhoptry is a specialized secretory organelle. They are club-shaped organelles connected by thin necks to the extreme apical pole of the parasite. These organelles, like micronemes, are characteristic of the motile stages of Apicomplexa protoz ...

, apical

polar ring Polar may refer to: Geography Polar may refer to: * Geographical pole, either of two fixed points on the surface of a rotating body or planet, at 90 degrees from the equator, based on the axis around which a body rotates * Polar climate, the c ...

(s), and a large food

vacuole A vacuole () is a membrane-bound organelle which is present in plant and fungal cells and some protist, animal, and bacterial cells. Vacuoles are essentially enclosed compartments which are filled with water containing inorganic and organic ...

(also called mucronal vacuole) having an outlet opening - a

cytostome A cytostome (from ''cyto-'', cell and ''stome-'', mouth) or cell mouth is a part of a cell specialized for phagocytosis, usually in the form of a microtubule-supported funnel or groove. Food is directed into the cytostome, and sealed into vacuo ...

. It is used to attach and to feed from the host's cell.Schrével J. (1971) Observations biologiques et ultrastructurales sur les Selenidiidae et leurs conséquences sur la systématique des Grégarinomorphes. Journal of Protozoology 18:448–479. https://doi.org/10.1111/j.1550-7408.1971.tb03355.xSchrével J, Valigurová A, Prensier G, Chambouvet A, Florent I, Guillou L. (2016) Ultrastructure of ''Selenidium pendula'', the type species of archigregarines, and phylogenetic relations to other marine Apicomplexa. Protist 167:339-368. https://doi.org/10.1016/j.protis.2016.06.001Simdyanov TG, Kuvardina ON. (2007) Fine structure and putative feeding mechanism of the archigregarine ''Selenidium orientale'' (Apicomplexa: Gregarinomorpha). European Journal of Protistology 43:17-25. https://doi.org/10.1016/j.ejop.2006.09.003 The epimerites of some aseptate eugregarines superficially (at the light microscopic level) resemble mucron and are usually called in the same way. This widespread misunderstanding originated from the conventional definition first proposed by Levine in 1971: " he mucron isan attachment organelle of aseptate gregarines. It is similar to an epimerite, but is not set off from the rest of the gregarine body by what appears under the light microscope to be a septum":Levine ND. (1971) Uniform terminology for the protozoan subphylum Apicomplexa. Journal of Protozoology 18:352-355. https://doi.org/10.1111/j.1550-7408.1971.tb03330.x thus, it may be equally applied to archigregarines and aseptate eugregarines as both they are aseptate. Note that the genuine epimerites are usually not separated by septa from the rest of the cell,Desportes I, Schrével J. (2013) Treatise on Zoology - Anatomy, Taxonomy, Biology. The Gregarines. Leiden: Brill. https://doi.org/10.1163/9789004256057 so this definition is actually misleading.

References

{{Alveolata Organelles Conoidasida