AMOEBOZOA

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Tubulinea

Tubular, subcylindrical pseudopodia or capable of altering the locomotive form from a flattened, expanded one to a subcylindrical one; with monoaxial flow of the cytoplasm in every pseudopodium or in the entire cell.

Discosea

Flattened naked amoebae, never producing tubular, subcylindrical pseudopodia and never altering the locomotive form; cytoplasmic flow polyaxial or without a pronounced axis; subpseudopodia short or absent, never both pointed and branched.

Archamoebae

Mitochondria converted to nonaerobic organelles.

Gracilipodida

Amoeboid without cilium or centrosomes; flattened, fan-shaped or irregularly branched, with short conical subpseudopodia or fine hyaline hair-like subpseudopodia; cysts with smooth single-layered.

Multicilia

Multiciliate, with ciliated single kinetosomes; conical microtubular cytoskeleton extending from every kinetosome; interkinetosomal fibres connect each kinetosome to a neighbouring one.

Protosteliida

Protosteloid sporocarpic amoebae typically with uninucleate amoebae containing light orange lipid drops, with acutely pointed subpseudopodia; one taxon amoebociliated with 1–9 reduced unikont kinetids not associated with nucleus; kinetids with only BB2, rootlets 1, 3, and 4, conical array (CA) of microtubules, and posterior parakinetosomal structure (PPKS); taxa without cilium with ring-shaped component in a nucleus-associated MTOC; mitosis with open spindle and either centrioles (one taxon) or ring-shaped MTOC at poles; cysts thinwalled, spherical to subspherical; amoebae that germinate from spores may fruit whether amoebociliated or not; prespore cells lozenge-shaped when viewed from above; sporocarps with long, delicate stalk supporting single spore, morphology varying by taxon.

Cavosteliida

Protosteloid sporocarpic with various types of amoebae, from uninucleate to plurinucleate amoebae to multinucleate reticulate plasmodia, all characterized by having long, filose, subspeudopodia, anastomosing in some taxa; one taxon amoebociliate with 1-several, reduced unikont kinetids per cell, not associated with the nucleus; kinetids with only BB2, rootlets 1, 3, and 4; taxon with amoebociliate has life cycle consistent with sex where amoebociliate germinates from spore then differentiate into a uninucleate obligate amoeba (Spiegel and Table 2. Classification of the higher ranks of the protists and multicellular groups. cont’d. ADL ET AL.—THE REVISED EUKARYOTE CLASSIFICATION 435 Feldman 1985) lacking kinetids that develop into sporocarp; all other taxa without amoebociliate state; only amoebae with no kinetids germinate from spores and then may develop into sporocarp; cysts thin-walled with various morphologies depending on taxon; prespore cells circular or lozenge-shaped when viewed from above; sporocarps with single, nondeciduous spores, morphology variable depending upon taxon, all with spores bearing some kind of sculpturing that varies by taxon.

Protosporangiida

Protosteloid sporocarpic with sexual life cycles where multiple, apparently haploid amoebociliates develop from germling of spore and then develop into apparently diploid obligate amoebae that are able to develop into sporocarps; germlings and amoebociliates covered with distinctive cell coat of fibres that branch at the apex; amoebociliates biciliate with nucleus-associated kinetids with rootlet 4 consisting of only 2 microtubules; prespore cells site of meiotic prophase; meiosis completed in spores.

Fractovitelliida

Protosteloid sporocarpic amoebae with no reported amoebociliate stage; amoebae flabellate with acanthopodial subpseudopodia, usually uninucleate with diffuse, multipart nucleolus; cysts thin-walled, spherical to irregular; prespore cells initially have “fried egg” appearance with rounded-up centre and thin, flat margin; sporocarps with deciduous spores, morphology varies by species.

Schizoplasmodiida

Protosteloid sporocarpic amoebae, all with multinucleate, reticulate plasmodia that have no directional streaming and a beaded appearance during mitosis; one taxon with amoebociliates that can develop from zoocysts derived from the plasmodium that germinates from the spore or from a fragment of a feeding plasmodium; one nucleus surviving in the zoocyst undergoes two to three rounds of nuclear division, hinting at meiosis, and cell division giving rise to four to eight scaled amoebociliates; kinetids bikont, lacking MTOC and CA; amoebociliate mitosis with open, centric spindle; prespore cells developing from multinucleate fragments of plasmodia; sporocarp stalk length variable according to taxon, but all stalks with cup-like apophysis that fits into annular hilum on spore; spores always multinucleate, shape varying according to taxon.

Myxogastria

Myxogastroid sporocarpic amoebae with trophic stage a free-living, multinucleate, coenocytic, saprobic multinucleate obligate amoeba (plasmodium); under poor conditions, plasmodium sometimes becomes a sclerotium; sporocarps (1 mm–1 m) developing from multinucleate obligate amoeba, the plasmodium, or fragment of plasmodium; most with stalked sporangia but also sessile sporangia, plasmodiocarps, aethalia or pseudoaethalia; stalks when present acellular; meiosis in uninucleate spores with sculptured spore walls, with spores produced in masses; spores in some suspended by thread-like acellular capillitium; haploid gametic amoebociliates in sexual species germinate from spores to trophic state that may alternate between a ciliated swarm cell and a nonciliated myxamoeba, or dormant thin-walled microcysts; kinetids closely associated with nucleus, present until mitosis then regenerating after telophase; kinetids as described for Amoebozoa; suspended amoebociliates twisted and obconic with distinct uroid; anteriorly directed cilium and shorter recurved posterior cilium in groove underlain by microtubule arrays 4, 5; mitosis centric and open; plasmodia developing from zygote in sexual species, directly from amoebociliate in apomictic species; plasmodium small and unveined with 8–100 nuclei (protoplasmodium) or large and veined network with 102 –4 9 107 nuclei with thick gel-like cortex shuttle in veins (phaneroplasmodium), or thin transparent veins (aphanoplasmodium); mitosis in plasmodium intranuclear with noncentric poles; dormancy as sclerotia of many macrocysts or as sporocarps.

Dictyostelia

Dictyostelia Lister 1909, emend. Olive 1970 Sorocarpic amoebae, known as the cellular slime moulds, with stalked fruiting bodies developing from aggregation of amoebae; sorocarps of stalks with terminal sori of haploid spores; stalks (sorophores), acellular (acytostelioid), cellular, and unbranched to sparsely branched (dictyostelioid) or cellular with whorls of branches (polysphondylioid); stalk cells forming cell walls and dying; spores usually ellipsoid, occasionally reniform or spherical; trophic amoebae, nonciliated, haploid, uninucleate; nuclei with reticulate peripheral nucleoli; microtubular cytoskeleton of amoebae radiating from lamellar discoid organelle near nucleus; amoebae of some species entering dormant stage as thin-walled microcysts; upon starvation, populations of amoebae becoming aggregation-competent, aggregating into multicellular aggregation centres in response to a chemical attractant called an acrasin; acrasins varying according to taxon; aggregated cells differentiating directly into subaerial sorogens that become sorocarps, or migrating along the substrate as slugs, prior to differentiating into sorogens that culminate as sorocarps; stalks produced by both migrating slugs and sorogens in most species, although a few species have stalkless migration; stalk tubes secreted by inner ends of cells at at least the anterior end of the slug/sorogen; in taxa with cellular stalks an anterior population of prestalk cells becoming enclosed in the stalk tube as the slug/sorogen advances, enlarging, secreting walls, vacuolating, and dying as mature stalk cells; remaining posterior prespore cells developing into spores suspended in a slime matrix; sexual, zygotic amoebae forming and acting as aggregation centres for haploid amoebae, which are ingested by the zygotes; entire small aggregate secreting a thick wall and then becoming a dormant macrocyst once all the haploid amoebae are ingested; meiosis occurring when dormancy of macrocyst is broken; haploid amoebae germinating from macrocyst. Note that classical taxa are not monophyletic and efforts at revision are still ongoing; four major clades recognized but not yet named (Romeralo et al. 2009, Schaap et al. 2006).

Incertae sedis Amoebozoa

Gibbodiscus, Hartmannia, Janickia, Malamoeba, Malpigamoeba, Echinosteliopsis oligospora Reinhardt and Olive 1966, Microglomus paxillus Olive and Stoianovitch 1977, Pseudothecamoeba, Stereomyxa, Thecochaos.

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