DESCRIPTION OF THE PHYLUM EOPHARYNGIA (CAVALIER-SMITH 1993)
| EUKARYA> EXCAVATA> EUEXCAVATA> EOPHARYNGIA |
EOPHARYNGIA LINKS
| Eophyringa (e-o-fi-RIN-ga) is made from a Greek and a Sanskrit word meaning before (eos -έως) and syphilis (phyringa a Sanskrit word). |
| INTRODUCTION TO THE EOPHYRINGA The eophyringids include Giardia and Chilomastix (Figures 1 and 2, respectively), taxa that are of some economic importance. Giardiasis is among the most common diseases from drinking contaminated water in the United States. In high rates of infection, Giardia can coat the mucosa of the small intestine (Figure 3) and inhibit the absorption of certain nutrients like vitamin B-12. Most of the known members of this phylum are parasites or commensals, though some are free-living. All members are amitochondriate and motile with four to six flagella, one of which is recurrent (text with tooltip) Recurrent flagella bend to the posterior end of the cell. Typically, they are identified as recurrent when anteriorly-directed flagella are present. and associated with the excavate (text with tooltip) An excavate is a feeding groove that terminates in a cytostome on the surface of certain taxa within the Excavata. Usually, they are associated with a recurrent or posteriorly-directed flagellum. . Part of their success as parasites comes from their ability to reproduce (asexually) by producing a resistant cyst (Figure 4). The eopharyngids are taxa with very deep branching when compared with other eukaryotes using single gene or small ribosomal RNA comparisons. Thus, those taxa and their related genera seemed to be among the most primitive of all living eukaryotes. The main problem with such a scenario is that eophyringids like Giardia and Chilomastix inhabit the gut. Secondary simplification and loss of mitochondria seem to be common in such lines. Supergroup analyses of the type presented by Baldauf (2003a), however, showed that members of this group were not diffuse up a eukaryotic tree of life but part of a coherent branch called the excavates that included trichomonads, parabasalids, jakobids, and metamonads. Figure 5 shows the eopharyngids as part of a clade of symbiotic unicells. The derived position is tentative and our interpretation of Lara et al. (2006), Kolisko et al. (2008), and Malik et al. (2011). |
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| FIGURE 1. (Left) SEM micrograph of a Giardia motile cell and illustrates the attachment suckers very well. (Right) High magnification light micrograph of a Giardia trophozoite stained with hematoxylin-eosin from a fecal sample. Left Image from the CDC, in the Public Domain Right Image from http://www.biosci.ohio-state.edu/~parasite/giardia.html | FIGURE 2. DIC micrograph of a Chilomastix motile cell. Note the anterior deep pocket from which the flagella emerge. Image from http://microscope.mbl.edu/baypaul/microscope/images/t_imgAZ/chilomastix_atw.jpg | FIGURE 3. An SEM micrograph of two Giardia trophozoites attached to intestinal mucosa. Image from http://www.uiowa.edu/~cemrf/archive/sem/large/Giardia.gif | FIGURE 4. High magnification light micrograph of a Giardia cyst from a fecal sample and stained with iodine. Image from the CDC, Public Domain |
 | FIGURE 5. The relationship of the classes of the Eopharyngia (in shaded box) relative to the other phyla in the Euexcavata (taxa in bold). The relationships given here have been inferred from Lara et al. (2006), Kolisko et al. (2008), and Malik et al. (2011). |
| LITERATURE CITED Baldauf, S. L. 2003a. The deep roots of eukaryotes. Science. 300 (5626): 1701-1703. Brugerolle, G., and J. P. Mignot. 1990. Retortamonadida. In: Margulis, L., J. O. Corliss, M. Melkonian, and D. J. Chapman, eds. 1990. Handbook of the Protoctista; the Structure, Cultivation, Habits and Life Histories of the Eukaryotic Microorganisms and Their Descendants Exclusive of Animals, Plants and Fungi. Jones and Bartlett Publishers. Boston. pp. 259-265. Cavalier-Smith, T. 2003a. Protist phylogeny and the high-level classification of Protozoa. European Journal of Protistology. 39:338-348. Dyer, B. D. 1990c. Parabasalia. In: Margulis, L., J. O. Corliss, M. Melkonian, and D. J. Chapman, eds. 1990. Handbook of the Protoctista; the Structure, Cultivation, Habits and Life Histories of the Eukaryotic Microorganisms and Their Descendants Exclusive of Animals, Plants and Fungi. Jones and Bartlett Publishers. Boston. pp. 252-258. [L] Grell, K. G. 1973. Protozoology. Springer-Verlag. New York. Kolisko, M., I. Cepicka, V. Hampl, J. Leigh, A. J. Roger, J. Kulda, A. G. B. Simpson, and J. Flegr. 2008. Molecular phylogeny of diplomonads and enteromonads based on SSU rRNA, alpha-tubulin and HSP990 genes: implications for the evolutionary history of the double karyomastigont of diplomonads. BMC Evolutionary Biology. 8: 205 doi: 10.1186/1471-2148-8-205 Kudo, R.R. 1966. Protozoology. 5th ed. Charles C. Thomas Publisher. Springfield. Lara, E., A. Chatzinotas, and A. G. B. Simpson. 2006. Andalucia (n. gen.) – the deepest branch within jacobids (Jacobida: Excavata), based on morphological and molecular study of a new flagellate from soil. Journal of Eukayotic Microbiology. (53(2): 112-120. Lee, J. J. 1985. Order Retortamonadida. In: Lee, J.J., S.H. Hunter, and E.C. Bovee, eds. An Illustrated Guide to the Protozoa. Allen Press. Lawrence, Kansas. pp. 118-119. Malik, S-B., C. D. Brochu, I. Bilic, J. Yuan, M. Hess, J. M. Logsdon, and J. M. Carlton. 2011. Phylogeny of parasitic Parabasalia and free-living relatives inferred from conventional markers vs. Rpb1, a single-copy gene. PLoS ONE. 6(6): e20774. doi:10.1371/journal.pone.0020774 Patterson, D. J. 1999. The diversity of eukaryotes. American Naturalist. 154 (Suppl.): S96–S124. Taylor, F. J. R. 1999. Ultrastructure as a control for protistan molecular phylogeny. The American Naturalist. 154(supplement): S125-S136. Vickerman, K. 1990a. Diplomonadida. In: Margulis, L., J. O. Corliss, M. Melkonian, and D. J. Chapman, eds. 1990. Handbook of the Protoctista; the structure, cultivation, habits and life histories of the eukaryotic microorganisms and their descendants exclusive of animals, plants and fungi. Jones and Bartlett Publishers. Boston. pp. 200-210. |
| By Jack R. Holt. Last revised: 02/17/2014 |
