Euglenids phylum Euglenozoa Euglenoidea

Euglenoidea consist of about 1000 species known mostly from aquatic habitats, but they are common in moist soil habitats. Modern treatment of this group can be found in Triemer and Farmer (1991) and in Leander and Farmer (2001). Cells are typically 10-50 ^m long, elongate or spindle shaped, with a deep (but sometimes inconspicuous) anterior invagination (Fig. 1.7). The invagination often functions as a cytostome and always contains two cilia. One cilium emerges

Fig. 1.6. Representative species of a Percolozoa, an Adelphamoeba showing the ciliated phase and the amoeba phase with eruptive clear lobopodia. Cilia (C), contractile vacuole (CV), lobopodium (LP), nucleus (N). Scale bar 25 ^m.

Euglenoidea

Fig. 1.6. Representative species of a Percolozoa, an Adelphamoeba showing the ciliated phase and the amoeba phase with eruptive clear lobopodia. Cilia (C), contractile vacuole (CV), lobopodium (LP), nucleus (N). Scale bar 25 ^m.

Euglenoidea
cilia, only one being emergent and visible by light microscopy. Scale bar 25 ^m.

from the cytostome, and the other may be very short and not emerging from the cytostome. The longer cilium often has a paracrystalline proteinaceous rod alongside the axoneme. An eye-spot of lipid vesicles occurs adjacent to a swelling at the base of the emergent cilium and the cytostome. The cilia bear non-tubular mastigonemes. In a few predatory species (cytotrophy on other protists), the cytostome can be a very elaborate organelle with mobile tooth-like elements. The storage material, paramylon, is an unusual molecule composed of P(1,3)-glucan polymer. The mitochondria have discoid cristae with constricted bases. The cell membrane is reinforced by strong interlinked strips (the pellicle) that wrap the cell. The pellicle provides stiffness and strength to the cell shape. Pellicle strips can move and bend in some species, allowing a form of amoeboid motion called metaboly. Permanently condensed chromosomes can be seen by light microscopy. Mitosis is closed, with an internal spindle, persistent nucleolus and slow asynchronous separation of chromosomes at anaphase. Conjugation with meiosis occurs in some species. Soil species are usually bacterivorous, osmotrophic or cytotrophic. About one-third of described species are photosynthetic, and some can be isolated from moist surface soil with adequate sunlight, where they appear in green patches. A group with few species, related to the euglenids, the Hemimastigophora (e.g. Hemimastix and Spironema) are about 10-60 ^m in length, vermiform, and have two spiral rows of cilia in a groove. Food vacuoles form at the anterior by phagocytosis, and the posterior can attach to the substrate.

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