| Parallel basal body/kinetosome
|
A pair of basal bodies/kinetosomes that have the same orientation. [Link to this definition]
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| PARASITE
|
An association of organisms in which one partner benefits to the detriment of the other. [Link to this definition]
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| Paratene
|
Repeating kinetid pattern perpendicular to the long axis of a ciliate giving the appearance of a circumferential rather than longitudinal kinety.This image shows the anterior paratenes of Dexiotricha granulosa (arrows). [Link to this definition]
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| PARAXIAL ROD
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A rod of material lying within the flagellum parallel to the axoneme, only found in some protists (e.g. euglenids) causing the flagellum to appear relatively thick (Fig. **). [Link to this definition]
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| Paraxonemal body (PAB)
|
Proteinaceous structure restricted to a certain area along the flagellum/cilium. A paraxonemal body occurs in chromophytes, euglenids and kinetoplastids; no homology is implied. Some PABs are autofluorescent, emitting green light when excited with blue light. PABs may play a role in phototactic photoreception. Some PABs are paracrystalline, linked to both the axoneme and paraxonemal fibers. "Flagellar spines" are a special type found in male gametes of oogamous brown algae. Synonyms: paraxial body, paraflagellar body (PFB), flagellar swelling. [Link to this definition]
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| Paraxonemal rod (PAR)
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Long, cylindrical structure (solid or hollow) that extends nearly the entire length of a flagellum/ cilium, located between the axoneme and flagellar membrane and usually connected to the axoneme and flagellar membrane by specific links. The paraxonemal rod occurs in dinoflagellates, euglenids, kinetoplastids, pedinellids and silicoflagellates. It may be very different in ultrastructure and biochemical composition in the different groups of protists and no homology is implied. Examples are the PAR of Euglena gracilis that is a paracrystalline, hollow structure that is non-contractile, the PAR in the transverse flagellum of dinoflagellates (= paraxonemal fiber) that is solid, cross-striated, contractile and contains the protein centrin, and the PAR of the longitudinal flagellum of dinoflagellates such as Gyrodinium that is a hollow cylinder composed of helically arranged fibrils. Synonyms: flagellar rod, paraxial rod, paraflagellar rod. [Link to this definition]
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| Paraxonemal structures (PAS)
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Structures embedded in the flagellar matrix that are not part of the axoneme but often connected to specific axonemal doublets. We distinguish at least two major types, paraxonemal body and paraxonemal rod. Synonyms: paraxial structures, paraflagellar structures. [Link to this definition]
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| PARTICLE
|
Small items (such as bacteria or protists), may be in suspension in fluid, or be associated with detritus or used in the manufacture of loricae/tests. Incomprehensibly referred to as 'particulates' by some. [Link to this definition]
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| Pedicel
|
see
Stalk.[Link to this definition]
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| Peduncle
|
Stalk. [Link to this definition]
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| pellicle
|
(1) Proteinaceous plate or plates located just underneath the plasma membrane in euglenoid flagellates. The individual plates (pellicular strips) may be capable of sliding along each other as in Euglena, or the plates may be firmly attached to each other as in Phacus. (2) In ciliates, \"pellicle\" is used to describe the outer part of the cell, comprising plasma membrane, alveoli, and the epiplasm , but it is only the outer portion of the entire ciliate cortex . (3) In dinoflagellates, it is used as a term for the \"wall\" of temporary cysts developing after the theca is shed by ecdysis. This type of pellicle comprises the fused inner amphiesmal vesicle membranes, an internal probably cellulosic layer and an external thin cellulosic (sometimes sporopollenin-containing) layer which originates from material present in the amphiesmal vesicles. (4) In various other protists (e.g., apicomplexans, opalinids, acantharians, scattered other taxa), \"pellicle\" has been used, rather loosely, for the plasma membrane plus any thickened material just below it, reminiscent of the terms \"cortex\" and \"ectoplasm\" . (5) The term \"pellicle\" has also been used to denote the skin-like aggregations of zygotes developing after clumping of gametes of opposite mating types in chlamydomonadalean flagellates. The pellicle of some euglenoid flagellates (e.g., Euglena spirogyra) is decorated by ferric hydroxide \"warts\". The term \"pseudopellicle\" has sometimes been used for euglenoid flagellates to describe the plasma membrane and the underlying proteinaceous plates. See Conclusions and recommendations; see also, Cuticle, Periplast. [Link to this definition]
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| Pellis
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Cuticle. [Link to this definition]
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| PENICULINE
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A type of oligohymenophoran ciliate (p. **) distinguished by the particular arrangement of the membranelles (e.g. Paramecium, Fig. **). [Link to this definition]
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| PENNATE
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One of two types of diatom (p. **), without radial symmetry, often able to move by gliding. [Link to this definition]
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| Peridium
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A covering enclosing spores within fruiting bodies. In Mycetozoa the peridium originates from material secreted as plasmodia differentiate into fruiting bodies. In zygomycetes the peridium is the original sporangial wall enclosing spores after they are cleaved from a multinucleate sporangium and produce spore walls . With fruitifications of higher fungi, the term is not restricted to extracellular material. Among rust fungi peridium pertains to the cup composed of hyphae surrounding aeciospores of fruiting bodies called aecia. [Link to this definition]
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| Perilemma
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[Link to this definition]
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| Periplast
|
In many protists, a colloquial term for a covering on the outside of the plasma membrane , e.g., “a scaly periplast”. In cryptomonad flagellates, a trilaminate structure consisting of proteinaceous inner and surface components that are closely associated with (i.e., “sandwich”) the plasma membrane. In euglenoid flagellates, sometimes used as a synonym of “pellicle” . In cryptomonad flagellates, the periplast covers the entire surface except for a subapical vestibulum from which the flagella emerge. Components are often composed of highly organized plate areas that correspond in size and position on either side of the plasma membrane. There is great variation on this simple theme; the inner component may consist of a single sheet or discrete plates that have variable relationships with the plasma membrane. The surface component, the details of which can only be viewed following freeze-fracture/etch, displays an even greater variation in structure; consisting of discrete plates or scales or fibrils or mucilage and combinations of any or all of these structures. See Conclusions and recommendations. [Link to this definition]
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| PERISTALSIS
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Regular contractions of a body or part of a body. Mostly said of the intestinal system of vertebrates but also the squirming behaviour of some euglenids. [Link to this definition]
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| PERISTOME
|
The region of the body around, and external to, the mouth. To deserve application of this term, the region must be modified to favour the acquisition of food. [Link to this definition]
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| PERITRICH
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A type of oligohymenophoran ciliate (STEP **) in which one membranelle and the undulating membrane are greatly lengthened and spiral around the oral end of the body (e.g. Vorticella, Fig. **). [Link to this definition]
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| Perizonium
|
see
Auxospore wall.[Link to this definition]
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| PETRI DISH
|
A low flat circular dish with vertical sides, made of glass or plastic and used extensively for the culture of micro-organisms - similar in shape to many centric diatoms. [Link to this definition]
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| PFU
|
PFU - abbreviation for Polystyrene Foam Unit, a sampling device, made of a piece of sponge polystyrene plastic - 5.0 X 6.5 X 7.5; usually immersed in an aquatic habitat for about 3 days, then removed, and the content squeezed out. A survey can be carried out on the organisms present in the resulting liquid. [Link to this definition]
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| PHAGOCYTOSE
|
To take food by phagocytosis, that is to ingestion of visible particles of food by enclosing them with a membrane to form a food vacuole. [Link to this definition]
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| PHAGOTROPH
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An organism which feeds by phagocytosis. [Link to this definition]
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| PHARYNX
|
A region of the ingestion apparatus lying internal to the mouth (of a metazoan organism) or internal to the cytostome of a protist. Involved in the swallowing process (see cytopharynx). [Link to this definition]
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| PHASE CONTRAST
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A method of contrast enhancement used widely in light-microscopy and particularly useful in protozoology. In this process, areas with differing refractive index appear darker or lighter than the background (Fig. **). [Link to this definition]
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| PHOTOMICROGRAPHY
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The process of taking photographs through a microscope [Link to this definition]
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| PHOTOSYNTHATES
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The products of photosynthesis [Link to this definition]
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| PHOTOSYNTHESIS
|
A means of acquiring energy for metabolism which involves trapping radiant energy in chloroplasts, the use of that energy to break up water molecules (hydrolysis) and to convert released energy into an accessible form - such as the molecule ATP. The only form of autotrophy in eukaryotic cells. Some heterotrophic protists have symbiotic algae which allow them to exploit photosynthesis. [Link to this definition]
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| PHOTOSYNTHETIC PIGMENTS
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Large molecules in chloroplasts that absorb radiant energy (hence they have colour), mostly chlorophylls and carotenes and, occasionally phycobilins. [Link to this definition]
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| PHYCOBILIN
|
A type of photosynthetic pigment, mostly found in blue-green algae, red algae, and some cryptomonads. [Link to this definition]
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| PIGMENTS
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Molecules which appear coloured. [Link to this definition]
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| PINOCYTOSIS
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A process of ingesting material by enclosing it with a membrane. The resulting structure is usually too small to be seen with the light microscope and is mostly suitable for the ingestion of fluid or mucus. [Link to this definition]
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| PIPETTE
|
A glass or plastic tube deigned to facilitate the processes of dispensing liquid. They may be graduated so that measured volumes may be dispensed. Pasteur pipettes have a narrow tip, but can be 'pulled' to a finer tip after heating so that they can be used for handling small volume of liquid or individual cells. Dropping pipettes are available from chemists and pharmacists, and have a rounded tip for safety. [Link to this definition]
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| PIXEL
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[Link to this definition]
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| PLANAR
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In one plane, for example of flagellar beating. [Link to this definition]
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| PLANKTON
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Organisms living in the water column (above the sediment). [Link to this definition]
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| PLANKTONIC
|
From the plankton, if protists may either be swimming or floating. [Link to this definition]
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| PLANT
|
Multicellular eukaryote with the capacity for photosynthesis using chlorophyll B and having cells surrounded by cellulosic walls. As with the term 'animal', 'plant' is sometimes inappropriately applied to unicellular organisms. To state that algae are unicellular plants is confusing, and the statement would be better if it said that algae are unicellular organisms with some characteristics (e.g. photosynthesis) that are also found in plants (or that plants are multicellular organisms with some specified characteristics that are also found in algae). For some, plants might include the multicellular plants, eukaryotic and prokaryotic algae, true fungi, oomycete fungi and even bacteria. [Link to this definition]
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| Plaque
|
(1) An organic plate-like structure cemented among the inorganic particles in the wall of testate amoebae; discoidal, with complex areolate or reticulated pore pattern in the central space. (2) In ciliates, a rectangular arrangement of intramembranous ultramicroscopic particles in the ciliary membrane covering a cilium, at the proximal end of the cilium. The plaques are secreted within Golgi-derived vesicles in the cytoplasm of testate amoebae, and are deposited by exocytosis on the surface of the newly formed cell during binary fission. Organic cement, secreted by other Golgi-derived vesicles, forms the matrix of the wall containing the plaques and test particles. Note that the term “adhesion plaque” [= “adhesion pad” ] has a different meaning. “Plaque” is also used in bacteriology to describe a clear zone in a bacterial lawn on a culture plate. See also, Pore plate. [Link to this definition]
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| Plasma membrane
|
With rare exceptions, the outermost living membrane of all protistan cells; therefore, the homologue of the universal limiting unit “cell membrane” of the cytological literature, possessing the same ultrastructure and general functions. While “cell envelope”, “cell membrane”, “cytoplasmic membrane”, and “plasmalemma” are often used as synonyms of “plasma membrane”, certain other terms may relate to structures that either sometimes include the cell membrane, e.g., the cortex and, in ciliates, but not in euglenoid flagellates, the pellicle , or are positionally in juxtaposition to it, e.g., the perilemma, an additional living membrane that lies just outside the plasma membrane (ciliary membrane), in some oligotrich ciliates and certain stichotrichous hypotrichs, and the alveoli , with their own unit membrane, lying just inside (under) it. Although we are not including motile appendages in our treatment, some remarks are made on clarifying the use of the term “membrane” and “membranelle”. The plasma membrane (often called the “ciliary membrane” by ciliatologists) of the cell body also encloses, without a break, the central axoneme of the protruding flagellum or cilium; whether such structures are present individually or, as in many ciliates, in some compound form. The latter are sometimes called a membrane or membranelle (e.g., the paroral or undulating membrane and the adoral zone of membranelles or polykineties of the oral or buccal area and the cirri on the ventral somatic surface of hypotrichs). See also, Glycocalyx. [Link to this definition]
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| PLASMODIUM
|
A type of amoeboid organization involving a large mass of cytoplasm and, usually, many nuclei. A type of body form adopted by some slime moulds. [Link to this definition]
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| PLASTID
|
The same as chloroplast, from it come the terms aplastidic and plastidic for with and without chloroplasts respectively. Chloroplasts are the site of photosynthesis, where radiant energy is trapped by the pigment and converted to chemical energy - for use by the cell. This image is of a Euglena, with green plate like chloroplasts. The colour of the plastids varies depending on which pigments are present. See colour.l [Link to this definition]
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| Plate
|
A relatively thin, flattened structure deposited on the surface of cells, usually inorganic (calcareous or siliceous) or organic as in the case of thecal plates in dinoflagellates; varying in geometry, circular, elliptical, quadrangular, or irregular in outline. Plates are secreted within cytoplasmic vesicles and deposited by exocytosis on the cell surface in some amoebae and centrohelidian heliozoa (or cysts in actinophrydian heliozoa), or enclosed in amphiesmal vesicles in dinoflagellates. A layer of skeletal plates is secreted within alveoli of the ciliate Euplotes. The plates may be planar to slightly concave, concavoconvex, or biconvex; perimeters variable, round to polygonal. Plates can be considered a form of scale or a synonym, but in general a plate is much thinner than broad, whereas a scale may be much more elaborate in three-dimensions. See also, Lorica, Periplast, Pore plate. [Link to this definition]
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| PLATYHELMINTH
|
Flatworm. [Link to this definition]
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| PODITE
|
A narrow extension from the posterior end of some ciliates and used for adhesion. Foot-like. [Link to this definition]
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| POLARIZING MICROSCOPY
|
A type of microscopy which produces bright images of objects which have a crystalline substructure. The process relies on the use of polarized light hence the term. [Link to this definition]
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| POLYHYMENOPHORA
|
A type of ciliate in which the buccal ciliature includes more than three membranelles. [Link to this definition]
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| Polykinetid
|
Organellar complex in ciliates composed of two or more kinetosomes, their cilia and associated infraciliary organelles that form cirrus or a membranelle.
[Link to this definition]
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| Polykinety
|
A closely spaced set of polykinetids (e.g. the adoral zone of membranelles). [Link to this definition]
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| POLYSACCHARIDE
|
A relatively large molecule comprised of many sugar molecules (chemically) joined together. Polysaccharides are relatively inert and may be used by cells to form external walls etc. Polysaccharides include cellulose, and starch. [Link to this definition]
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| POMIFORM
|
Shaped like an apple (as of some helioflagellates). [Link to this definition]
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| Pore plate
|
An organic or mineralized septum containing pores. In foraminifera, some pores in the shell contain septa, spanning the opening usually at a position below the rim, and penetrated by micropores that often contain thin, cytoplasmic projections. A fine silicified plate with pores that span the areola of the frustule of many diatoms. An organic, sometimes partially silicified, areolate plate or plaque is deposited in the test of some testate amoebae. [Link to this definition]
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| POSTERIOR
|
That part of the body away from the direction of normal movement or away from the mouth. The term 'back ' may also be used, but this can be confused with 'dorsal' [Link to this definition]
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| PROKARYOTE
|
A type of organisms, the cells of which are without nuclei or other membrane-bound organelles (= bacteria). [Link to this definition]
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| Properizonium
|
see
Auxospore wall.[Link to this definition]
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| PROSTOME
|
A type of ciliate with the mouth located at the anterior end of the body and usually ingesting larger particles of food (e.g. Coleps). [Link to this definition]
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| PROTOSTELID
|
A type of slime mould, spores usually produced by a single cell rather than a mass of cytoplasm as is the case for most slime moulds. [Link to this definition]
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| PROTOZOA
|
Those heterotrophic and (a few) autotrophic protists which have, by tradition, been studied by protozoologists. Some people prefer the broader term 'protist', but protozoas is still widely used for flagellates, ciliates, amoebae, and sporozoa without chloroplasts. [Link to this definition]
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| PROXIMAL
|
Near to (compare distal). [Link to this definition]
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| Pseudopellicle
|
see
Pellicle.[Link to this definition]
|
| PSEUDOPODIUM
|
Transient extensions of the cell surface, used for locomotion or feeding. Plural: [Link to this definition]
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| PUNCTATE
|
With a dimpled or spotted appearance. [Link to this definition]
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| Pustule
|
Blister-like, papillate, or knob-like projection on the surface of a cell enclosure, or eruptive spot or spore mass in fungi. Pustules occur as calcified projections on the outer surface of foraminiferal shells, or as ornamentations on the surfaces of frustules and thecae of some algae. [Link to this definition]
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| PUSULE
|
A system involving a sac and channels and found in some dinoflagellates. The function is not understood, but may act as an osmoregulatory organelle. [Link to this definition]
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| PYRENOID
|
A protein body lying inside some types of chloroplasts. [Link to this definition]
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