DESCRIPTION OF THE PHYLUM JAKOBADA (CAVALIER-SMITH 1993)
| EUKARYA> EXCAVATA> EUEXCAVATA> JAKOBADA |
JAKOBADA LINKS
| Jakobada (ja-KO-ba-da) is named for a common genus, Jacoba. |
| INTRODUCTION TO THE JAKOBADA The jakobids (e.g. Jakoba, Figure 1) form a small group of free-living biflagellated cells that have been only recently recognized as a coherent group (O’Kelly 1993a, Patterson 1999, Simpson and Patterson 1999 and 2001, Edgcomb et al. 2001, and Cavalier-Smith 2003b). The unicells may be attached or free-swimming (freshwater and marine). They have a well-developed feeding groove or 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. . Unlike most other euexcavates, they have mitochondria and can be found in parts of the water column where oxygen is plentiful. The primitive nature of the cells and of the mitochondrial genomes have lent some support to the Excavate Hypothesis (Simpson and Patterson 1999 and 2001) which states that all members of the excavata evolved from a small free-living group (similar to the jakobids) with a feeding groove. The phylum as it is defined here is a modification of Patterson (1999), Cavalier-Smith (2003a and 2003b), and Simpson (2003). In particular, we have combined the core jakobids (e.g. Jakoba) with Malawimonas (Figure 2), a similar excavate biflagellate, according to Cavalier-Smith (2003) and Lara et al. (2006). O’Kelly (1993a) discusses three genera that we have placed in Jakobea and suggests that until more is known about them and their relationships with other eukaryotic taxa, a formal taxonomic system should not be used that includes them. Lara et al. (2006) compared taxa within the Jakobea, including a recently discovered genus, Andalucia and confirmed that Jakobea is monophyletic and that Malawimonas is its sister (Figure 3). |
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| FIGURE 1. Light micrograph of Jakoba, one of the core jakobids. Right Image from http://microscope.mbl.edu/baypaul/microscope/images/ | FIGURE 2. Malawimonas, a biflagellate excavate that is similar to the core jakobids. Right Image from http://microscope.mbl.edu/baypaul/microscope/images/ |
 | FIGURE 3. A cladogram showing the relationships between the phyla of the Euexcavatae (taxa in bold). The jakobids (in the shaded box) are part of the free-living clade. The relationships given here have been inferred from Lara et al. (2006), Kolisko et al. (2008), and Malik et al. (2011). |
| LITERATURE CITED Cavalier-Smith, T. 2003a. Protist phylogeny and the high-level classification of Protozoa. European Journal of Protistology. 39:338-348. Cavalier-Smith, T. 2003b. The excavate protozoan phyla Metamonada Grasse emend. (Anaeromonadea, Parabasalia, Carpediemonas, Eopharyngia) and Loukozoa emend. (Jakobea, Malawimonas): their evolutionary affinities and new higher taxa. International Journal of Systematic and Evolutionary Microbiology. 53:1741-1758. [ Edgcomb, V. P., A. J. Roger, A. G. B. Simpson, D. T. Kysela, and M. L. Sogin. 2001. Evolutionary relationships among “jakobid” flagellates as indicated by alpha- and beta-tubulin phylogenies. Molecular Biology and Evolution. 18(4):514-522. O’Kelly, C. J. 1993a. The Jakobid flagellates: structural features of Jakoba, Reclinomonas and Histonia and implications for the early diversification of eukaryotes. J. Euk. Microbiol. 40(5):627-636. Patterson, D. J. 1999. The diversity of eukaryotes. American Naturalist. 154 (Suppl.): S96–S124. Simpson, A. G. B. 2003. Cytoskeletal organization, phylogenetic affinities and systematics in the contentious taxon Excavata (Eukaryota). International Journal of Systematic and Evolutionary Microbiology. 53: 1759-1777. Simpson A. G. B. and D. J. Patterson. 1999. The ultrastructure of Carpediemonas membranifera: (Eukaryota), with reference to the ‘excavate hypothesis’. European Journal of Protistology. 35: 353-370. Simpson, A.G. B., and D. J. Patterson. 2001. On core jakobids and excavate taxa: the ultrastructure of: Jakoba incarcerata. Journal of Eukaryotic Microbiology. 48: 480–492 & 2001. Taylor, F. J. R. 1999. Ultrastructure as a control for protistan molecular phylogeny. The American Naturalist. 154(supplement): S125-S136. |
| By Jack R. Holt. Last revised: 02/17/2014 |
