| Hair scales
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Tubular flagellar hairs assembled in the Golgi apparatus and consisting of carbohydrates primarily, forming two rows along the longitudinal axis of the flagellum and attaching to axonemal B-tubules Numbers 4 and 8. Hair scales occur on scaly flagella of green algae. [Link to this definition]
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| HAIRS
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Thin stiff appendanges, may be hairs on a flagellum, from a lorica, or from the body. [Link to this definition]
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| Haptonema
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A filamentous appendage that is (usually) relatively long, consisting of an extension of the plasma membrane, a sheath of endoplasmic reticulum, and a core of several microtubules anchored near the basal bodies/kinetosomes. Haptonemata occur on many motile prymnesiophytes (= haptophytes). Superficially, they resemble flagella/cilia when viewed with a light microscope, but their ultrastructure indicates they do not originate from axonemes. Haptonemata that are long may contract quickly to form a coil at the base of the flagella/ cilia. The functions of haptonemata include attachment and food collection. [Link to this definition]
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| HAPTORID
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A type of ciliate preying on other protozoa, usually other ciliates, capturing and/or killing them with explosive extrusomes [Link to this definition]
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| HELICAL
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Of a helix, like a spiral but extending in the third dimension. This is a fluorescence micrograph of the spiral bacterium Spirulina. [Link to this definition]
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| HELIOFLAGELLATES
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Flagellates with stiff radiating arms around the flagellum; two categories pedinellid (e.g., Actinomonas, Fig. **), and dimorphid. [Link to this definition]
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| HELIOZOON
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A type of protist with stiff radiating arms (e.g. Acanthocystis, Actinophrys, Figs **, **). Plural, heliozoa; adjective, heliozoan. The heliozoan body form has evolved on several occasions. [Link to this definition]
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| HETEROCYST
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A differentiated, thick-walled, cell found in filaments of some blue green algae. [Link to this definition]
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| HETEROTRICH
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A type of polyhymenophoran ciliate (STEP **) moving by means of individual cilia arranged in kineties. [Link to this definition]
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| HETEROTROPHIC
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A mode of nutrition in which the consumer relies upon molecules created by other organisms for energy and nutrients. Either osmotrophic (absorbing soluble organic matter) or phagotrophic (ingesting particles of food). [Link to this definition]
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| Holdfast adhesion
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Extracellular matrix , mucilaginous secretion, cementing one end of a filament, typically via a morphologically distinct holdfast cell, to a substrate. Found with single algal filaments, particularly in shallow aquatic habitats. In actual use the term holdfast sometimes applies to a cell, to extracellular matrix, or to both a cell and secreted adhesive matrix. This term is also used among fungi such as with trichomycetes inhabiting guts of arthropods as commensals. The sessile state of the ciliate Stentor and many other sessile protists also produces an adhesive attachment at the posterior end. See also, Adhesions, Adhesion pad, Holdfast organelle, Stalk. [Link to this definition]
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| Holdfast organelle
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Term broadly used in protozoology in reference to any structure(s) by which a given organism can affix or attach, temporarily or permanently, to some living or inanimate substrate. A wide range of organelles, often specialized and involving secreted or otherwise formed non-living and/or living structures, are implicated: e.g., cilia (individual or in thigmotactic fields), flagella, pseudopodia, tentacles, tails, suckers, hooks, spines, epimerites, sucking discs, threads, filaments, stalks of diverse kinds and loricae . As widely used by protozoologists, these diverse holdfast or adhesive organelles go beyond the rather restricted concepts of adhesions and holdfast adhesion as defined above. [Link to this definition]
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| HOLOTYPE
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In nomenclature, the single specimen or other object that serves as the definitive reference for the name of a species or infraspecific taxon (e.g. subspecies, variety). If the author of a species conserves five specimens of the organism being defined (a "type series"), one is designated as the holotype, the other four are designated ISOTYPES or PARATYPES. That way, if the five specimens all prove to belong to different species (this has happened), the name is anchored precisely to the holotype. [Link to this definition]
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| Homothetogenic fission
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Type of cell division typical of most ciliates,usually transverse(i.e. perkinetal). There is a point-to-point correspondence between structures of the proter and the opisthe. [Link to this definition]
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| House
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see Lorica. [Link to this definition]
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| HYMENOSTOME
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A type of oligohymenophoran ciliate (STEP **) with buccal ciliature comprised of three membranelles and an undulating membrane (e.g. Colpidium). [Link to this definition]
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| HYPERSALINE
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A type of habitats with unusually high concentrations of salt. This picture is of a small pool of sea water which has become isolated from the sea and from which evaporation has taken place until the salt has begun to crystallize. An extreme habitat. [Link to this definition]
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| HYPHAE
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Feeding and growth elements of fungi, long thin tubes with occasional cross-walls. The cytoplasm moves towards thje growing tips of the hyphae. Typically branching. Old hyphae may lack cytoplasm. Collections of hyphae are usually visible to the named eye as a fluff. [Link to this definition]
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| Hyphal sheath
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Sheath. [Link to this definition]
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| Hyphal sheath
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see
Sheath.[Link to this definition]
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| HYPOSTOME
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A type of ciliate with mouth located ventrally, hence the name, used in reference to cyrtophorine ciliates which use a basket of nemadesmata to aid the ingestion of food. (e.g. Pseudomicrothorax, Trithigmostoma) [Link to this definition]
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| Hypothallus
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A thin clear crust at the base of fruiting bodies of some Mycetozoa. This structure is continuous with the acellular stalk (see Stalk) and appears as a disc. In protostelids this structure is also called a “basal disc” and in certain slime molds the hypothallus may be a continuous structure interconnecting the bases of multiple fruiting bodies. In coralline red algae the term “hypothallus” (= “hypothallium”) is used for the lower part of the thallus composed of large cells. [Link to this definition]
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| HYPOTRICH
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A type of polyhymenophoran ciliate which moves using cirri [Link to this definition]
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