| ABORAL
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Relating to position - away from the mouth (contrasts with adoral which means near the mouth). This Stentor niger is attached to the substrate by its aboral end. [Link to this definition]
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| ACELLULAR STALK
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see
Stalk.[Link to this definition]
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| ACRONEMATIC
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A term that describes a feature of flagella in which there is a thinner region near the tip (distal). The arrow shows where the trailing flagellum of Rhynchomonas nasuta changes thickness, it is acronematic to the left of the arrow. [Link to this definition]
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| ACTINOPHORE
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A structure of suctorians bearing a fascicle (bundle) of tentacles (e.g. Lernaeophrya capitata). [Link to this definition]
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| ACTINOPHRYID
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A type of heliozoon characterised by arms that clearly taper from base to tip, with two common genera Actinophrys (with one central nucleus - and illustrated here) and Actinosphaerium (with many nuclei). Probably related to some of the stramenopile (chrysophyte) algae. [Link to this definition]
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| ACTIVATED SLUDGE PLANT
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Part of one type of modern sewage treatment process in which sewage is violently aerated and which (typically) supports large populations of ciliated protozoa. [Link to this definition]
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| ADAPTIVE STRATEGY
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A suite of linked properties of an organism which together make it more competitive. Often said of evolutionary trends in which convergence is evident (e.g., sessile habit, colonial habit, etc.). [Link to this definition]
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| ADHERING
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= attached. This Petamolonas boadicea is characterised by the adhering scales. [Link to this definition]
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| ADHESION PAD
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A type of extracellular matrix which spreads at the cell or spore substrate interface, binding the two surfaces together. “Adhesion pad”, “adhesion plaque”, “mucous pad” and “spore tip mucilage” are used as synonyms. The polarized distribution of this material distinguishes it from an extracellular matrix or sheath . Among oomycetes it attaches encysting zoospores to a host or substrate; among pennate diatoms it denotes distinct, localized regions of polysaccharide adhering cells together into colonies; among pedinellid flagellates (such as Apedinella) it is a surface associated structure that spine-scales attach to. Adhesion pads may have diverse origins including: (1) discharge from pre-existing organelles such as K-bodies as oomycete zoospores are induced to encyst and (2) selective secretion of polysaccharide from localized pores on the frustule surface of diatoms. Adhesion pads of diatoms are a specialized part of the non-silicified, organic casing and maintain connections between daughter cells following division. The exact position of these pads determines the overall morphology of the colony. An adhesion disc made of denticles (ring) immediately beneath the pellicle occurs in the ciliate Trichodina. See also, Adhesions, Holdfast adhesion, Plaque, Stalk. [Link to this definition]
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| Adhesion plaque
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see
Adhesion pad.[Link to this definition]
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| Adhesions
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Morphologically and chemically diverse classes of compounds which function in attachment of cells to substrates or hosts. Distributions of adhesions at the cell surface range from adhesive junctions to the entire cell surface. Symphoriontic ciliated protozoa, for example, attach to host carapaces with stalks that have adhesive bases. Fine pseudopodia in amoeboid protists that adhere closely to the substratum are categorized as adhesive. See also, Adhesion pad, Holdfast adhesion, Holdfast organelle. [Link to this definition]
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| ADORAL
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Relating to position - near the mouth. In this Epistylis cell, the mouth is in the middle at the top of the bell. and the cilia which form a wreath around the anterior of the cell might be referred to as adoral. The opposite is aboral, the stalk is aboral. [Link to this definition]
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| ADORAL ZONE OF MEMBRANELLES
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A band of membranelles found in polyhymenophoran (spirotrich) ciliates which extends from the front of the cell to the cytostome. Mostly used for feeding, but occasionally for locomotion. This image is of Condylostoma, and the AZM sweeps around the anterior of the cell and down to the mouth - located just below the edge of this image. Sometimes referred to as a 'collar-and-lapel' arrangement. [Link to this definition]
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| aff.
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Abbreviation of Latin "affinis", meaning "related". Used in nomenclature to indicate that a specimen is probably related to, but not identical with, the taxon named. Example: Tetrahymena aff. pyriformis indicates that the specimen probably belongs to the Tetrahymena pyriformis species (or species complex), but its exact taxonomic placement is uncertain. [Link to this definition]
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| AGAR
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Commercially available gelling material which is used as a basis for cultures of bacteria, fungi and some protozoa. Add 1.5 grams per 100 mls of water, and heat indirectly in a water bath, pour into petri-dishes or equivalent containers when molten. [Link to this definition]
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| AGGLUTINATED
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Sticking/stuck together, often said of tests of some protozoa which are made from pieces of debris (xenosomes) that adhere to each other. This is an image of a difflugiid testate amoeba with a lorica of small pieces of grit. [Link to this definition]
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| ALGAE
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Organisms capable of photosynthesis without relying on symbiotic organisms. May be prokaryotic = bacterial (blue-green algae = cyanobacteria) or eukaryotic in which case mostly (some say exclusively) protists. Said of, for example, green algae, brown algae, diatoms, chrysophytes (chrysoflagellates), red algae, and cryptophytes (cryptoflagellates). All contain pohotosynthetic pigments. [Link to this definition]
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| ALORICATE
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No lorica present. This is the naked bicosoecid flagellate, Cafeteria. [Link to this definition]
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| ALVEOLI
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Membrane-bounded flattened vesicles or sacs underlying the plasma membrane in certain protists, most notably, the (majority of the) ciliates, the dinoflagellates [where they are called “amphiesmal vesicles” ], some sporozoan (apicomplexan) parasitic protists, and possibly the glaucophyte algal protists. A single alveolar vesicle is also known as a “lacuna”, and the entire system in ciliates has been called a “lacunar system” in older literature. In more recent usage, it is called pellicular alveoli. A similar system found in the Sporozoa is known as “inner membrane complex”. In some actinopods (e.g., radiolaria) an organic capsular wall surrounding the central cell mass is deposited within lacunae resembling alveoli. The flattened peripheral cisternae underlying the plasma membrane of oomycete zoospores may well deserve consideration as a kind of alveoli. In diatoms, the term alveoli is used for elongated chambers of the valve opening to the inside of the cell by a large opening and with a perforate outer layer. See Conclusions and recommendations; see also, Cortex, Epiplasm, Pellicle. [Link to this definition]
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| AMOEBA
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Protists which move and feed using pseudopodia - temporary extensions of the cell surface. In this image of Mayorella, the pseudopodia are short and conical and arising from the upper part of the cell. [Link to this definition]
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| AMOEBOID
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Like an amoeba, usually means that the organism has the capacity to produce pseudopodia. This image is of Pelomyxa. It is amoeboid, producing pseudopodia at the front (to the right) and has a uroid at the posterior of the cell. [Link to this definition]
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| Amphiesmal vesicles
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see
Amphiesma.[Link to this definition]
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| AMPHITROPHIC
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Said of organisms capable of gaining energy and nutrients by both autotrophic and heterotrophic means. This is Prorodon, a ciliate with symbiotic algae, which means that it can carry out photsynthesis, but it also has a mouth and can ingest other protists as food - the dark inclusions are partly digested food. The terms amphizoic and mixotrophic are virtually interchangeable. [Link to this definition]
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| AMPHIZOIC
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Said of organisms capable of gaining energy and nutrients by both autotrophic and heterotrophic means. This is Paramecium bursaria, a ciliate with symbiotic algae, which means that it can carry out photsynthesis, but it also has a mouth and can ingest bacteria - attention is drawn to a food vacuole with an arrow. The terms amphitrophic and mixotrophic are virtually interchangeable. [Link to this definition]
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| AMPULLAE
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Part of the contractile vacuole complex of some protists, distensible channels found in the vicinity of contractile vacuoles. Clasically in Paramecium, the ampullae being the 9 distended structures around the contractile vacuole to the right of this cell. [Link to this definition]
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| ANALOGUE
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Said of electronic images formed of a continuously variable signal - as opposed to digital. Most video media are analogue, domestic televisions mostlyu work with analogue signals. [Link to this definition]
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| ANASTOMOSE
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Said of pseudopodia which branch and fuse, thereby forming a network. In this case, in Theratromyxa [Link to this definition]
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| Angled basal body/kinetosome
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A pair of basal bodies/kinetosomes in which the angle subtended by the long axes of the basal bodies is greater than 0° but less than 180°, most commonly approximately orthogonal. [Link to this definition]
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| Animals
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Multicellular eukaryotes, mostly with cells arranged in epithelia (layers attached to collagenous base) gaining energy and nutrients by ingesting particles of food - or clearly related to such organisms. The invertebrates and vertebrates. Inappropriately used in reference to protists, for example when protozoa are referred to as unicellular animals. This is a gastrotrich. [Link to this definition]
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| ANOXIC
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No free oxygen present - a situation that commonly arises in natural habitats when the biological demand for oxygen exceeds the supply - for example in sediments or when a site is organically polluted. [Link to this definition]
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| ANTERIOR
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The front part of the cell. Usually determined as being in the direction of normal movement. [Link to this definition]
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| Antiparallel basal body/kinetosome
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A pair of basal bodies/kinetosomes that have opposite polarity and whose bases are adjacent or nearly so. [Link to this definition]
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| APERTURE
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An opening, used in relation to tests or loricae to refer to the site of emergence of pseudopodia, flagella, or cell. This is the ventral face of the testate amoeba, Arcella, with its central aperture. [Link to this definition]
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| APEX
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The most anterior point of a cell. [Link to this definition]
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| APICAL
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Pertaining to apex, the anterior pole. [Link to this definition]
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| Apokinetal
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Type of ciliate stomatogenesis in which the oral apparatus of the opisthe develops de novo, without association with the structures of the parental oral apparatus. [Link to this definition]
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| Appressorium ring
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Extracellular matrix in an o-ring like arrangement through which the penetration peg from the appressorium of some pathogenic fungi, such as rust fungi, passes just prior to entering host cells. Believed to assist in attachment of appressorium to host cell and preventing dislodgement as host colonization occurs. [Link to this definition]
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| AQUATIC
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Watery - as in aquatic habitat (ponds, lakes, streams, oceans, etc). [Link to this definition]
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| ARBORESCENT
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Type of colony with a tree-like branching pattern. This is rhipidodendron, a colonial heterotrophic flagellate. [Link to this definition]
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| AREOLA
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Plural: areolae. Pore, usually more or less circular, in the diatom frustule, usually restricted to the valve. The pore may be partially occluded by a FORAMEN, or completely occluded by a CRIBRUM in which there may be tiny pores (CRIBRELLA). Occurrence, distribution and detailed structure of areolae are among the characters used to identify diatom genera and species.
[Link to this definition]
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| ARM
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Long thin non-motile projection from a cell - as of pseudopodia of heliozoa (or feeding tentacles of suctoria - such as this Heliophrya. [Link to this definition]
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| ATHALAMIDA
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Type of amoeba with filose pseudopodia and no shell - usually regarded as related to foraminifera. [Link to this definition]
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| ATTACHED
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Adhering to a fixed point of the substrate - either permanently (cannot easily detach) or temporary (can easily let go). [Link to this definition]
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| ATYPICAL
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Unusual, normally said of an organism which is quite unlike other members of its group. [Link to this definition]
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| AUTOTROPHIC
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Organisms which trap energy from physical or chemical sources and use the energy to assemble the macromolecules of which they are made. Photosynthesis is the only process by which this happens in eukaryotes, but additional processes are found among prokaryote organisms. Compare with heterotrophic. [Link to this definition]
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| Auxospore wall
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The cell wall of a diatom auxospore (a cell resulting from sexual fusion or autogamy, or one formed purely by vegetative processes that swells to maximum size). The auxospore wall differs from that of the normal vegetative cell. Its primary wall consists of polysaccharide material, which in most centric diatoms contains overlapping siliceous scales . Auxospores may also develop a secondary wall system consisting of siliceous hoops or bands, collectively termed the “perizonium” (in pennate diatoms) and “properizonium” (in centric diatoms), respectively. Unlike the perizonium, the properizonium is not separated spatially from the primary auxospore wall, but is physically and developmentally continuous with it. The individual siliceous components of the perizonium (properizonium) resemble modified girdle bands, and are secreted sequentially to create the secondary auxospore wall. The new frustule of the enlarged initial cell is deposited within the perizonium (properizonium), which then ruptures to release the cell. [Link to this definition]
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| AXIS
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A conceptual line passing from the anterior pole of the cell to the posterior pole. [Link to this definition]
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| Axoneme
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An axial array of (usually) 9 outer doublet and 2 central microtubules used to support flagella, the arms of heliozoa, etc. The basic architecture of the axoneme is presumably universal in eukaryotic cells and includes: outer doublet microtubules, central pair of microtubules, outer and inner dynein arms, nexin links, radial spokes, central sheath, etc. This does not mean that axonemes in different protists are identical in molecular or fine structural terms. Typically, the doublet microtubules consist of one complete microtubule with 13 subunits (A-tubule) and one partial microtubule with 10-11 subunits (B-tubule). Individual doublet microtubules can often be distinguished because variability exists in paraxonemal structures or cell surface components that enable specific doublet labeling. Some axonemal components may be modified or missing in the different protist groups. For example, the central pair of microtubules may be missing (especially in flagella/cilia that are not involved in motility), special dynein arms may be present, and septations may occur within the lumen of the B-tubules. [Link to this definition]
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| AZM
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Abbreviation for Adoral Zone of Membranelles - a band of membranelles found in polyhymenophoran (spirotrich) ciliates which extends from the front of the cell to the cytostome. Mostly used for feeding, but occasionally for locomotion. This image is of Condylostoma, and the AZM sweeps around the anterior of the cell and down to the mouth - located just below the edge of this image. Sometimes referred to as a 'collar-and-lapel' arrangement. [Link to this definition]
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