Cryptomonadales with special emphasis on Pyrenomonadaceae

Markus Majaneva

University of Helsinki

CRYPTOMONADS (Cryptomonadales Pascher) are unicellular,mainly pigmented, biflagellated eukaryotes that thrive in aquatic environments. They gained photosynthetic ability from a secondary endosymbiosis between an aplastidial phagotrophic ancestor and a red alga. In addition to the plastid genome, cryptomonads have retained a reduced red algal nucleus in a form of a nucleomorph.Cryptomonads are easily identified by the presence of aventrally located cell invagination (the groove/furrow or the gullet or both) that is lined with ejectisomes and that extends posteriorly from an anterior depression (the vestibulum), an asymmetric cell shape, two anterior flagella, and their typical swaying swimming pattern. However, taxonomy and systematics below the class level are difficult because few characters are visible under the light microscope with the consequence of a confused nomenclature.Cryptomonadales includes four major families: Pyrenomonadaceae, Chroomonadaceae, Geminigeraceae and Cryptomonadaceae. Attempts to revise the taxonomy using cell ultrastructure have been hampered by contradictory molecular phylogenies and discovery of dimorphic forms. Recently, members of the genera Cryptomonas and Hemiselmis have been successfully revised based on a combination of electron microscopy and molecular phylogenetic analyses.The family Pyrenomonadaceae is distinguished from other cryptomonads by the position of the nucleomorph that bisects the pyrenoid and biliprotein phycoerythrin 545. The familyincludes three genera: Rhodomonas, Rhinomonas andStoreatula. Rhodomonas species have a furrow, squared inner periplast plates, and fibrillated surface periplast. Rhinomonas species lack the furrow and have hexagonal inner periplast plates. Storeatula species lack the furrow, have a sheet-like inner periplast and a dense mat of fibrils on the surface periplast component. Recent molecular phylogenetic studies with limited species sampling within the family have shown that the genera might not be monophyletic.

Family Pyrenomonadaceae

Family Chroomonadaceae

Family Geminigeraceae

Family Cryptomondaceae

Goniomonas

Basal Cryptophyceae

The family Pyrenomonadaceae includes three clades: Clade A, Clade B, and Clade C. All Rhinomonas sequences branch within the Clade C, while the genus Rhodomonas is paraphyletic. The analyses suggest that the genus Storeatula is an alternating morphotype of the genera Rhinomonas and Rhodomonas and that the family Pyrenomonadaceae includes some species thatwere described multiple times, as well as novel species.

Majaneva, M., Remonen, I., Rintala, J.-M., Belevich, I., Kremp, A., Setälä, O., Jokitalo, E. and Blomster, J. (2014), Rhinomonas nottbecki n. sp. (Cryptomonadales) and Molecular Phylogeny of the Family Pyrenomonadaceae. Journal of Eukaryotic Microbiology, 61: 480–492.