Home / Dinoflagellates / Nonphotosynthetic / Oxyrrhis
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Name derivation:
From the Greek, oxys, sharp, and rhis, nose.
Classification:
Order Oxyrrhinales; Family Oxyrrhinaceae Oxyrrhis has a tenuous classification, described as a very primitive dinoflagellate "at best", with trichocysts that differ from those of cryptomonads (Hall 1957). It is generally classified as a primitive dinoflagellate based on protein phylogenies (Saldarriaga et al. 2003; Gile et al. 2006) while cell morphology is typical of cryptomonads. It also has flagellar apparatus comparable to some dinoflagellates (Roberts 1985).
Morphology:
Heterotrophic grazer. Lacks chlorophyll but is not colorless, having a faint pink color. It has the general shape of other cryptomonads, including a subapical groove, two equal flagella with a subapical insertion, and no heavy cellulose "armor" plates . It also has no cingulum and no sulcus. Some classify it as a colorless dinoflagellate -- but it is at best an outlier of the dinoflagellates.
Similar genera:
Chilomonas, another colorless cryptomonad, closely resembles Oxyrrhis under the light microscope.
Habitat:
Common in temperate to tropical marine habitats, including estuaries, marshes, and tidepools. Our specimen were found in a red-colored rock pool on the coast of New Hampshire. The organisms' bloom is responsible for the pink-to-red water color likely as a result of having ingested (by phagotrophy) purple sulfur bacteria.
Secondary Phototrophy:
Thought to have evolved from photosynthetic predecessors, Oxyrrhis has acquired a gene by lateral transfer, perhaps from its purple bacterial prey, that enables it to produce rhodopsin. As a result it may be acquiring some energy from light absorption, and may also enhance its digestive ability, These, it is argued, are not sensory in nature (Slamovits et al. 2011).
Grazing:
Oxyrrhis is a size-selective grazer, selecting the largest prey it can handle with its transverse flagellum in experiments where it is presented with a range of prey sizes from 2 – 10 µm (Hansen et al. 1996).
References:
Gile, H.G., N.J. Patron, and P.J. Keeling 2006. EFL GTPase in Cryptomonads and the distribution of EFL and EF-1a in chromalveolates. Protist 157(4):435-444. Dujardin, F. 1841. Histoire naturelle des Zoophytes, Infusoires, comprenant la physiologie et la clasification de ces animaux et la manière de les étudier à l'aide du microscope. pp. i-xii, 1-684. Paris: Librarie Encyclopédique de Roret Guiry, M.D. & Guiry, G.M. 2013. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway. http://www.algaebase.org; searched on 8 November 2013. Hall, R.P. 1957. Cytoplasic inclusions of the plant-like flagellates. III. Bot. Rev. 23(5):313-319. Hansen, F.C., H.J. Witte, and J. Passarge. Grazing in the heterotrophic dinoflagellate Oxyrrhis marina: size selectivity and preference for calcified Emiliania huxleyi cells. Aquatic Microbial Ecology 10:307-313. Roberts, K.R. 1985. The flagellar apparatus of Oxyrrhis marina (Pyrrophyta). J. Phycol. 21(4):641-655. Saldarriaga, J.F. M.L. McEwan, N.M. Fast, F. J. R. Taylor and P.J. Keeling 2003. Multiple protein phylogenies show that Oxyrrhis marina and Perkinsus marinus are early branches of the dinoflagellate lineage. Internat. J. of Systematic and Evol. Microbiology 53:355-365. Slamovits, C.H., N. Okamoto, L. Burri, E.R. James, and P.J. Keeling 2011. A bacterial proteorhodopsin proton pump in marine eukaryotes. Nature Communications 2 Article 183:1-6. (online)