Chilomonas Ehrenberg, 1831

Lectotype species: Chilomonas paramaecium Ehrenberg

Currently accepted name for the type species: Cryptomonas paramaecium (Ehrenberg) Hoef-Emden & Melkonian

Original publication: Ehrenberg, C.G. (1831). Animalia evertebrata exclusis insectis Series Prima cum tabularum decase prima. In: Symbolae physicae. (Hemprich, P.C. & Ehrenberg, C.G. Eds), pp. [1-71]. Berolini [Berlin]: ex officina academica.

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Type designated in: Senn, G. (1900). Flagellata: Pantostomatineae, Protomastigineae, Distomatineae, Chrysomonadinea, Cryptomonadineae, Chloromonadineae, Euglenineae, Anhang zu den Flagellata. In: Die natürlichen Pflanzenfamilien. (Engler, A. & Prantl, K. Eds) Vol. 1(1), pp. 93-188, figures 63-140. Leipzig: Wilhelm Engelmann.

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Description: Free-swimming, biflagellate monads, generally obovoid often with a recurved posterior sometimes produced to acutely pointed; not known to produce palmelloid colonies. A longitudinal furrow extends posteriorly from the vestibulum and transforms into a sack-like gullet lined with many rows of ejectisomes. With a single nucleomorph but lacking a chloroplast and pyrenoid; with a prolific accumulation of peripheral starch granules. Periplast with a laminate inner component and a superficial layer of fine fibrillar material. Sexual reproduction is unknown; reproduction being through simple cell division. Cyst formation is unknown. Mitosis has been examined by light microscopy and there are several reports on the number of chromosomes in Chilomonas paramecium. The parasite Spiromonas perforans has been observed to infect Chilomonas paramecium. A slightly unusual ultrastructure in that the plastidial complex lacks a chloroplast and pyrenoid. Instead, a leucoplast is present with the nucleomorph and starch occupying the periplastidial compartment. The inner periplast component is porous with ejectisomes occupying the pores and providing attachment to the plasma membrane. The flagellar apparatus has been reconstructed; the rhizostyle has keel-like projections running down its convex surface. A detailed ultrastructure of the ejectisomes has been reported. The genus has a cosmopolitan distribution in freshwater habitats, including temporary ponds, rivers and lakes. Some species have been described from brackish and marine habitats. Most species are known only from European waters. It is probable that the number of species will be reduced after taxonomic revision. There is an isolated report of Chilomonas paramecium being toxic. The 16s-like ribosomal RNA gene has been cloned from the nucleomorph genome of Chilomonas paramecium. It is considered that the presence of the nucleomorph in Chilomonas paramecium indicates that its heterotrophic state is secondarily derived.

Information kindly contributed by D.R.A. Hill but may now be outdated.

Taxonomic status: This name is currently regarded as a synonym of Cryptomonas.

Most recent taxonomic treatment adopted: Kawai, H. & Nakayama, T. (2015). Introduction (Heterokontobionta p.p.), Cryptophyta, Dinophyta, Haptophyta, Heterokontophyta (except Coscinodiscophyceae, Mediophyceae, Fragilariophyceae, Bacillariophyceae, Phaeophyceae, Eustigmatophyceae), Chlorarachniophyta, Euglenophyta. In: Syllabus of plant families. Adolf Engler's Syllabus der Pflanzenfamilien. Ed. 13. Phototrophic eukaryotic Algae. Glaucocystophyta, Cryptophyta, Dinophyta/Dinozoa, Haptophyta, Heterokontophyta/Ochrophyta, Chlorarachnniophyta/Cercozoa, Chlorophyta, Streptophyta p.p. (Frey, W. Eds), pp. 11-64, 103-139. Stuttgart: Borntraeger Science Publishers.

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Some of the descriptions included in AlgaeBase were originally from the unpublished Encyclopedia of Algal Genera, organised in the 1990s by Dr Bruce Parker on behalf of the Phycological Society of America (PSA) and intended to be published in CD format. These AlgaeBase descriptions are now being continually updated, and each current contributor is identified above. The PSA and AlgaeBase warmly acknowledge the generosity of all past and present contributors and particularly the work of Dr Parker.

Descriptions of chrysophyte genera were subsequently published in J. Kristiansen & H.R. Preisig (eds.). 2001. Encyclopedia of Chrysophyte Genera. Bibliotheca Phycologica 110: 1-260.

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M.D. Guiry in Guiry, M.D. & Guiry, G.M. 26 May 2017. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway.; searched on 30 September 2023

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