This glossary contains the terms found in the printed volume of Antarctic Marine Protists. It is based largely on definitions provided in the following texts: for diatoms, Medlin & Priddle (1990: 67–81), Round et al. (1990: 1–58) and Hasle & Syvertsen (1997: 14–20); for dinoflagellates, Steidinger & Tangen (1997: 390–416); for coccolithophores, Heimdal (1997: 744–749); for protozoa, Corliss & Lom (1985: 576–602), Patterson & Hedley (1992: 193–206), Hausmann & Hülsmann (1996: 301–311) and Throndsen (1997: 600–602).
References used in the compilation of the Antarctic Marine Protists Glossary
Corliss, J.O. & Lom, J. (1985), An annotated glossary of protozoological terms. In Lee, J.J., Hutner, S.H. & Bovee, E.C. (eds), An Illustrated Guide to the Protozoa. (Society of Protozoologists, Allen Press, Lawrence). pp. 576–602.
Hasle, G.R. & Syvertsen, E.E. (1997), Marine diatoms. In Tomas, C.R. (ed.), Identifying Marine Diatoms and Dinoflagellates. (Academic Press, San Diego). pp. 5–385.
Hausmann, K. & Hülsmann, N. (1996), Protozoology. (Thieme, New York and Stuttgart). 338 pp.
Heimdal, B.R. (1997), Modern coccolithophorids. In Tomas, C.R. (ed.), Identifying Marine Diatoms and Dinoflagellates. (Academic Press, San Diego). pp. 744–749.
Medlin, L.K. & Priddle, J. (eds) (1990), Marine Polar Diatoms. (British Antarctic Survey, Cambridge). 214 pp.
Patterson, D.J. & Hedley, S. (1992), Free-living Freshwater Protozoa. A Colour Guide. (Wolfe, London). 223 pp.
Round, F.E., Crawford, R.M. & Mann, D.G. (1990), The Diatoms. Biology and Morphology of the Genera. (Cambridge University Press, Cambridge). 747 pp.
Steidinger, K.A. & Tangen, K. (1997), Dinoflagellates. In Tomas, C.R. (ed.), Identifying Marine Diatoms and Dinoflagellates. (Academic Press, San Diego). pp. 387–589.
Throndsen, J. (1997), The planktonic marine flagellates. In Tomas, C.R. (ed.), Identifying Marine Diatoms and Dinoflagellates. (Academic Press, San Diego). pp. 591–730.
AAC: of coccolithophores, an antapical coccolith (e.g. in Pappomonas).
acicular: spindle- or needle-shaped.
acronematic: of a flagellum, terminating in a narrow hair-point.
actinopod: a ray-shaped pseudopodium.
adhesive disc (= basal disc): of ciliates, a cup-shaped organelle at the posterior pole of a ciliate used for attachment to a substratum.
adoral zone of membranelles (= oral polykinetid zone): of ciliates, a band of membran-elles along the left and sometimes anterior sides of the oral area.
agglutinated: of ciliates, lorica wall composed entirely of foreign particles which are added during construction and held together by an organic cement.
aklitolophic: of ciliates, type of brosse; orientation is parallel to somatic kineties and these are not inclined upon the brosse.
ala: of prasinophytes, Pterosperma, a wing-like projection on the outer surface. pl. alae.
aloricate: without a lorica.
alveolus: of diatoms, an elongated chamber running from the central part of the valve to the margin, open to the inside and covered by a perforated layer on the outside. pl. alveoli.
amoeba: a member of the Class Lobosea; a protist that uses pseudopodia. pl. amoebae.
amphiesmal plates (= thecal plates): of armoured dinoflagellates, plates composed of cellulose or other polysaccharide microfibrils binding the cell.
ampulla: of ciliates and euglenoids, an anterior invagination of the cell.
anisokont: having flagella of unequal length and/or characteristics; usually one flagellum with flagellar hairs, the other smooth.
annulus: of diatoms, a ring of costal thickness, often surrounding one or more processes and with a structure different from that of the rest of valve. adj. annulated.
antapex: the posteriormost part of cell body excluding spines and similar structures.
antapical plates: of dinoflagellates, thecal plates that surround and touch the antapex of the cell.
antapical pole (= foot pole): of diatoms, mainly used for cells in stellate, radiating and bundle-shaped colonies in which neighbouring cells are joined by valve faces of the antapical poles. cf. apical pole.
anterior: that part of the organism which leads in forward movement.
antiligula: a small projection on diatom copulae (girdle bands) on the opposite side of the ligula.
aperture: an opening; used in relation to loricae or tests to indicate the site of emergence of the flagella or pseudopodia; of diatoms, the space between adjacent valves of a chain.
apex: the anteriormost part of a cell.
apical groove: a groove at a cell apex composed of many thecal vesicles.
apical plane: perpendicular to the transapical axis.
apical plates: of dinoflagellates, those thecal plates that surround and touch the apex of the cell.
apical pole (= head pole): of diatoms, used mainly for cells in stellate, radiating and bundle-shaped colonies in which neighbouring cells are joined by valve faces of the antapical poles. The apical pole is the tip of the other end of the cell. cf. antapical pole.
apical pore field: of diatoms, an area of small pores at the apices of the valves, usually in longitudinal rows.
apical slit field: of diatoms, an area of elongate pores (slits) at the apices of the valves, usually in longitudinal rows.
araphid: of diatoms, those with a simple raphe that runs the length of the valve.
arcuate: curved like a bow.
areola: a regularly repeated perforation through a diatom valve wall. pl. areolae.
areolate: of diatoms and dinoflagellates, ornamentation in the form of deep or shallow depressions on thecal plates or valves.
armoured (= thecate): referring to cells with an identifiable theca or cell wall.
asexual reproduction: whereby a haploid cell produces 2 or 4 cells with the same chromosome number as their parent.
auxotroph: a photosynthetic organism that requires only supplementary organic substances (e.g. vitamins). adj. auxotrophic.
axial cross: of coccolithophores, a structure spanning the central area of a coccolith, with longitudinal and transverse cross-bars, e.g. in Pappomonas weddellensis, and Papposphaera spp.
axis: a conceptual line passing through specified parts of a cell.
axoneme: the group of microtubules (9 × 2 + 2 structure) constituting the active part of the flagellum.
axopod/axopodium: of a centrohelid heliozoan, a thin, straight pseudopodium with an internal skeletal structure comprising microtubules.
band/segment: a single element of a diatom girdle.
basal part: of diatoms, Family Chaetoceraceae, that portion of a seta closest to the valve face; that portion of an inner seta between its point of origin on valve face and its point of crossing with its sibling setae.
basal siliceous layer: of diatoms, a layer that forms the basic structure of the various components of the frustule.
BC: of coccolithophores, a body coccolith (e.g. in Pappomonas).
benthic: referring to organisms living on the sea-bed.
biarcuate: having two adjoining bow-like curves.
bifurcated: forked, divided into two parts.
bilabiate process: of diatoms, a process consisting of an shorter or longer external tube, sometimes reduced to a low ring (LM), and an internal part with a longer or shorter stalk and a trapezoidal end-piece closed at the tip but open at each of the two slanting sides by a longitudinal split.
bilateral/bilateral symmetry: of diatoms, having valve striae arranged basically in relation to a line, so that the cell appears to have identical left and right halves.
binary fission: an asexual mode of reproduction.
biotope: the living space of a community of organisms (plants, animals and microorganisms).
blue-green algae: members of the Class Cyanophyceae.
bloom: an overabundant growth of organisms, often caused by nutrient enrichment.
box scale: of prasinophytes, a box-shaped, organic scale on the outer surface of the cell body.
bristles: of ciliates, stiff and rather immobile cilia (long or short) of several kinds and functions.
broad girdle view: a diatom frustule seen from the broad side.
brosse (= dorsal brush, terminal fragment): of ciliates, one or several, often short kineties near anterior of cell (usually dorsal), often orientated obliquely to the long body axis.
buccal cirrus: of spirotrich ciliates, usually one or a few cirri close to the right and often near the anterior end of the paroral membrane.
c.: circa (about).
calyx: of coccolithophores, a flaring structure at the tip of a process, e.g. in Papposphaera spp.
canal raphe: of diatoms, a system consisting of raphe canal, fibula and raphe keel.
cancellate: of Granuloreticulosa, latticed.
caneolith: of coccolithophores, a disc- or bowl-shaped heterococcolith with a lath-filled central area (e.g. in Syracosphaera).
capitate: having a knob-like head or tip.
caudal: of ciliates, relating to or in the position of a tail.
caudal cilium: of ciliates, a distinctly longer somatic cilium at or near the posterior pole of a cell body.
caudal cirri: of spirotrich ciliates, at or near the posterior margin of dorsal surface and at the ends of dorsal kineties.
central nodule: of diatoms, Family Bacillariaceae, a bridge of silica separating two raphe slits, often thicker than the rest of the valve.
central pore: of diatoms, Family Bacillariaceae, a pore-like expansion of the central raphe ending.
central raphe ending: of diatoms, Family Bacillariaceae, the central end of a raphe slit, when the raphe consists of two slits.
centric: referring to diatoms of the Order Centrales.
centrohelid: a type of heliozoan with thin, parallel-sided arms with prominent extrusomes.
centroplast: of a centrohelid heliozoan, the single, centrally located, microtubule organising centre (MTOC) from which all axopods arise.
CFC: of coccolithophores, a circum-flagellar coccolith (e.g. in Pappomonas).
chains: of diatoms, cells joined by threads from strutted processes (Thalassiosira), by external parts of strutted processes (Skeletonema), by abutting of valve faces (Leptocylindrus), by external part of the single labiate process, contiguous area and claspers (Rhizosolenia), by bipolar elevations (Eucampia), by bipolar elevations with spines (Ceratulina), by setae (Chaetoceros) or by a marginal ridge (Lithodesmium).
chlorophyll: a group of green pigments having the vital function of absorbing light energy for photosynthesis.
chlorophyte (= green alga): a member of the Class Chlorophyceae.
chloroplast: a membrane-bound cell organelle containing chlorophyll.
choanoflagellate: a member of the Class Craspedophyceae/Choanoflagellida.
chromatin: chromosomal material consisting of DNA and proteins within the cell nucleus which becomes deeply stained with basic dyes.
chromosome: an assemblage of molecular DNA in the nuclei of eukaryotic cells, containing genetic information.
chrysophyte (= golden-brown flagellate): a member of the Class Chrysophyceae.
ciliate: a member of the Phylum Ciliophora.
ciliferous: of ciliates, bearing cilia.
cilium: of ciliates, a hair-like projection associated with locomotion, having a 9 × 2 + 2 axonemal arrangement as found in flagella. pl. cilia.
ciliary row: see kinety.
ciliature: the total assembly of oral and somatic cilia or cirri; may be arranged in patches, kineties, membranes or membranelles.
cingulum (= girdle, transverse groove): of dinoflagellates, a furrow encircling a dinoflagellate cell once or several times, either circular, displaced, median, postmedian or premedian in location; of diatoms, a portion of a diatom girdle associated with a single valve; part of the frustule between upper and lower valves. adj. cingular.
circular cingulum: of dinoflagellates, a cingulum that is not displaced and in which the proximal end meets the distal end.
circumoral: of ciliates, surrounding the oral area.
cirrus: of ciliates, compound somatic ciliature; a cluster of cilia functioning as a single unit in locomotion or food collection, but with no common enveloping membrane. pl. cirri.
claspers: of diatoms, Family Rhizosoleniacea, a pair of membranous structures that unite adjacent cells by wrapping around the otaria.
coccoid: a cell with a firm outer wall, without flagella.
coccolith: plate-like, calcified scales formed in vesicles of the endoplasmic reticulum of coccolithophorid haptophytes.
coccolithophore: a member of Order Coccolithophorales.
coccosphere: the spherical cell of a coccolithophore.
collar: a hollow, cone-shaped circle of minute, finger-like processes projecting from the apex of choanoflagellate cells.
colony: a localised population of organisms derived from a single cell.
contiguous area: of diatoms, Family Rhizosoleniaceae, part of the ventral side of the valve contiguous with the adjacent valve of linked cells, usually delimited by low, marginal ridges.
contractile vacuole: a membrane-bound cavity located peripherally in the cell, associated with the expulsion of fluid and serving as an osmoregulator in the cytoplasm.
cortex: of ciliates, the complex outer cell layer including pellicle and infraciliature.
cortical granules: of ciliates, small, often refractile granules in the periphery of a cell, sometimes corresponding to extrusomes (e.g. mucocysts). Colour, shape and arrangement are important species characteristics.
costa: of diatoms, a siliceous rib on valve surface; of choanoflagellates, siliceous strips or rods from which the lorica is built.
coxlielliform: of tintinnid ciliates, lorica shape as in genus Coxliella.
crenulate: with a regularly indented margin.
cribrum: of diatoms, velum of a valve perforated by regularly arranged pores. pl. cribra.
cristallite: of coccolithophores, a minute crystal.
cryptophyte: a member of the Class Cryptophyceae.
cyanophyte (= blue-green alga, cyanobacterium): a member of the Class Cyanophyceae.
cyrtocyst: of ciliates, a type of subpellicular extrusome found in Didinium.
cyrtos: of ciliates, a type of tubular cytopharyngeal apparatus; often curved, with walls strengthened by longitudinally arranged nematodesmata. Derived from apically located kinetosomes and lines with extensions of postciliary microtubules; does not contain toxicysts.
cytopharynx: of ciliates, a non-ciliated, tubular passageway leading from the cytostome into the inner cytoplasm of the organism. adj. cytopharyngeal.
cytoplasm: that part of the living contents of a cell not located within the nucleus. adj. cytoplasmic.
cytostome: of ciliates, a cell mouth or oral opening; a two-dimensional aperture, most commonly open, through which food passes into the cytoplasm.
cyst: a bladder or bag-like structure that may contain the resting stage of an organism.
decussate: in alternating pairs.
detritus: fragments of dead biological material before, during and after decay, sometimes incorporating inorganic matter.
diatom: a member of the Class Diatomophyceae/Bacillariophyceae.
dikinetid: of ciliates, a morphological complex of two neighbouring (paired) basal bodies (kinetosomes) along with associated cilia and infraciliary organelles.
dinoflagellate: a member of the Class Dinophyceae.
diploid: a cell (zygote) that has a nucleus with two sets of chromosomes. abbrev. 2n.
dithecate: of coccolithophores, cells having two discrete layers of different types of coccoliths, the endothecal and exothecal layers.
dorsal: the uppermost side, or back, of an organism.
dorsal brush: of ciliates, one or several short kineties near the anterior end of a cell.
double-eurystomous type: of euplotid ciliates, a type of dorsal silverline system; one longitudinal silverline in the middle between each of two dorsal kineties connected with transverse silverlines so that two longitudinal rows of equally long rectangles are formed.
double-patella type: of euplotid ciliates, a type of dorsal silverline system; one longitudinal silverline eccentric between each of two dorsal kineties connected with transverse silverlines so that two longitudinal rows of unequal rectangles (one large, one very small) are formed.
elevation: of diatoms, Family Eupodiscaceae, a raised portion of a valve wall, not projecting laterally beyond the valve margin, which may bear some special structure; otherwise with the same structure as valve.
encystment: process of forming a protective stage in a life history in which an organism surrounds itself with a cyst wall.
endoral membrane: of ciliates, a row of cilia extending on the bottom and right border of the oral cavity.
endostyle: of loricate peritrich ciliates, an internal stalk connecting a zooid to the bottom of lorica or (when present) to the septum (an extra layer of material forming internal lining in lorica).
endosymbiont: an organism living within a dissimilar organism in a relationship in which both partners benefit. adj. endosymbiotic.
endotheca: the inner layer of coccoliths of a dithecate coccolithophore. adj. endothecal.
entoecism (= inquilism): of ciliates, an intimate (transitional) association between two organisms (usually animals) in which one partner lives within the host body to obtain shelter but without parasitising it. adj. entoecic.
epibiotic: an organism that grows attached to the outside of another living organism.
epiphytic: a plant that grows attached to the outside of another plant, using it only for support, but doing it no harm.
epizoic: an organism that grows attached to the outer surface of an animal.
equant: equal in size and form.
ER: Endoplasmic Reticulum, a series of interconnected, flattened, subcellular cavities.
eukaryote: any cell or organism comprised of cells that possess a membrane-bound nucleus, several chromosomes, cellular organelles and accomplishes cell division by mitosis and meiosis. adj. eukaryotic; cf. prokaryote.
euglenoid: a member of the Class Euglenophyceae.
euhedral: of crystals, characterised by well-developed crystal faces (external surfaces).
exotheca: the outer layer of coccoliths of a dithecate coccolithophore. adj. exothecal.
extrusome: of ciliates, a membrane-bound, subpellicularly located extrusible body of various, probably non-homologous types (e.g. cyrtocysts, mucocysts, pexicysts, toxicysts, trichocysts).
extrusome warts: of ciliates, Genus Loxophyllum, protruding, wart-like structures along dorsal margin containing groups of extrusomes (toxicysts).
fascia: of diatoms, Family Achnanthaceae, an extension of the central area forming a hyaline (unperforated) band extending the valve, i.e. transapically.
fasciculate areolation: of diatoms, valve striae (and, therefore, areolae) grouped in discrete sectors (fascicles).
fenestra: a small, window-like perforation. pl. fenestrae; adj. fenestrated.
Feulgen-stained: material treated with a histological stain selective for DNA.
filopodium: of amoebae, a filiform pseudopodium with a pointed tip, capable of rather rapid movement, used for locomotion and food uptake.
filose: of amoebae, of the Class Filosea.
filter feeding: a type of feeding in which suspended particles are concentrated and ingested by means of cilia or flagella directing a current of water to the cell, and a filter to trap and concentrate the particles before enclosure within a food vacuole.
flagellum: a fine, whip-like process associated with locomotion, normally with the typical 9 × 2 + 2 microtubular arrangement of the axonemes. pl. flagella; adj. flagellar, flagellate, flagellated.
flagellar pore: of dinoflagellates, a pore through which a flagellum emerges.
flimmer hairs: of chrysophytes, minute tubular hairs along all or part of the flagellar axis.
food vacuole: a fluid-filled space within the cell cytoplasm delimited by a membrane, the repository for food particles ingested by phagocytosis.
footprint scale: of prasinophytes, a minute, organic body scale in the shape of a human footprint.
foramen (= aperture): of diatoms, an opening or passage through the constriction at the valve surface opposite the velum. pl. foramina.
Formvar: a material for producing very thin films for supporting material on electron microscope grids.
frontal cirri: of spirotrich ciliates, near the anterior end of a cell, often slightly enlarged.
frontal plate: of ciliates, a non-ciliferous, often transversely truncate apical area.
frontoterminal cirri: of urostylid ciliates, a short row of cirri that originates during morphogenesis near the transverse cirri and migrates anteriorly close to the right end of the adoral zone of membranelles.
frontoventral cirri: of spirotrich ciliates, a group of cirri between the anterior portion of the right-marginal cirral row (or the right body margin in euplotids) and the paroral membrane.
fusiform: swollen at the middle and tapering towards each end; narrowly ellipsoidal.
frustule: the silica-containing wall of a diatom.
gamete: a haploid cell that fuses with another to produce a diploid zygote. adj. gametic.
genuflexed: bent like a knee.
girdle: of diatoms, part of a frustule between the upper and lower valves; of strombidiid ciliates, referring to transverse orientation.
girdle view: of diatoms, a view of the cell with the valves seen in profile and the girdle seen in face view.
gullet: of cryptophytes, the buccal cavity at the cell apex from where the two flagella arise.
gyre: a coil.
haploid: a vegetative or gametic organism in which the nucleus contains one set of chromosomes. abbrev. n/1n.
haptonema: of haptophytes, an organelle formed as a microtubular appendage, serving as a holdfast or for crawling or food uptake.
haptophyte: a member of the Class Haptophyceae.
helicolith: of coccolithophores, a placolith with a spiral pattern and marginal flange which overlaps adjacent helicoliths (e.g. Helicosphaera carteri).
helictoglossa: of diatoms, Family Bacillariaceae, an inwardly projecting structure resembling a rolled tongue, located at the distal end of a raphe on the internal valve surface.
herbivorous: of an organism that feeds exclusively on plant material. n. herbivory.
heterokont: of dinoflagellates, biflagellate, with one smooth flagellum and the other covered with mastigonemes.
holdfast: the basal part of an organism attaching it to the substratum.
holotrichous: of ciliates, having the entire body completely and ±uniformly ciliated.
horn: of diatoms, Family Asterolampraceae, a long, narrow elevation; of dinoflagellates, prominent extensions of the cytoplasm covered by thecal plates of epi- or hypotheca.
hyaline: colourless and transparent.
hyaline band: of diatoms, an element of a girdle lacking perforations.
hyaline ray: of diatoms, Family Asterolampraceae, raised openings in the valve face, open to the interior of the valve by elongate, slit-like openings, open to the exterior through holes at the marginal ends of the rays.
infraciliature: of ciliates, the total assembly of somatic and oral basal bodies and their associated subpellicular microfibrillar and microtubular structures.
inner seta: of diatoms, an intercalary seta or a seta occurring within the chain of cells. pl. setae.
intercalary plate: of dinoflagellates, thecal plates not in contact with the apex or the cingulum (for anterior intercalary plates), or with the antapex or the cingulum (for posterior intercalary plates).
interstria: of diatoms, the non-perforate, siliceous strips between two striae. pl. interstriae; adj. interstrial.
invagination: inpushing of a layer of cells; or a concave structure (e.g. cell surface, oral area) in unicellular organisms.
in vivo: in reference to a living organism.
interstrial costa, interstrial membrane: of diatoms, a siliceous rib on a valve surface in the space between two striae.
investment: a covering or coating.
keel: see raphe keel.
kinetid: of ciliates and flagellates, basal apparatus of cilia and flagella, consisting of at least one kinetosome with all associated rootlets (monokinetid), but also of two (dikinetid) or more kinetosomes (polykinetid).
kinetofragmon: of ciliates, Family Kryoprorodontidae, a short (curved) row of somatic cilia transversely on lateral side of body, very likely a reduced spiral kinety.
kinetosome (= basal body): of ciliates, a subpellicularly located basal termination of cilia, cylindrical and composed of 9 peripheral microtubular triplets; may be non-ciliferous.
kinety: of ciliates, a structurally and functionally integrated row of single or paired somatic kinetids, often running longitudinally.
kummerform: in reference to the final chamber of a whorl being reduced in size.
laevogyre: of coccolithophores, elements and sutures that curve to the left when traced radially outward, e.g. in Calcidiscus leptoporus.
lamina: of ciliates, a layer. adj. laminal.
lanceolate: narrow with curved sides tapering to a pointed end.
lateral: of, at, towards or from the side.
lath/lath-like element: of coccolithophores, a thin strip of crystalline structure.
left: left-hand (view or side) in relation to dorsal surface.
life cycle: the continuum of phases and cell types in the growth and reproduction of an organism.
ligula: a small, tongue-like projection on diatom copulae. pl. ligulae.
limulus scale: of prasinophytes, a minute, organic body scale in the shape of a horseshoe crab.
linking spines: of diatoms, Family Fragilariaceae, marginal spines that link sibling valves in a chain.
list (= wing, flange): a membranous extension of an armoured dinoflagellate.
LM: light microscope/microscopy.
lobopodium: in amoebae, a lobe-like pseudopodium with a rounded termination, used for locomotion and food uptake.
loculus/loculate areola: of diatoms, an areola (pore) markedly constricted at one surface of the valve and occluded by a velum at the other.
lorica: of choanoflagellates, siliceous investment surrounding a cell body; of ciliates, not only of siliceous material but also, e.g. proteinaceous or of mucopolysaccharides. adj. loricate.
lorica chamber: a cavity created by a choanoflagellate lorica.
macrozoospore: of the haptophyte Phaeocystis, a comparatively large, motile, flagellated spore capable of vegetative multiplication.
mammiform: swollen, with a small, nipple-like projection.
marginal cirri: of spirotrich ciliates, one to few rows of cirri along lateral cell margins.
marginal ridge: of diatoms, a ridge between the valve face and the valve mantle, continuous or interrupted, perforated or solid.
mastigoneme (= flimmer): a hair-like projection of the flagellar shaft.
median cingulum (= equatorial girdle): of dinoflagellates, a cingulum located approx-imately at the midpoint of the cell.
membrane: a thin sheet of organic material in protists, plants and animals.
membranelle (= polykinety): of ciliates, a compound structure comprising many cilia, and associated with the mouth of a ciliate; present either in groups of 3 or as a band of many more.
mesoplankton: plankton organisms in the size range 200–2000 µm. adj. mesoplanktonic.
mesostyle: of loricate peritrich ciliates, a short, broad and non-contractile internal middle stalk between septum (extra layer in lorica) and base of lorica.
metaboly: mobility and the ability to change the shape of the cell.
micronucleus: of ciliates and foraminiferans, a small, germline nucleus that shows little or no gene expression, but with the potential to undergo meiosis; found in cells exhibiting nuclear dimorphism. cf. macronucleus.
microplankton: plankton organisms in the size range 20–200 µm. adj. microplanktonic.
microtubule: a thin, proteinaceous tubule acting as a supporting, cytoskeletal element within protist cells.
microzoospore: of the haptophyte Phaeocystis, a comparatively small, motile, flagellated spore capable of vegetative multiplication.
midventral cirri: of spirotrich ciliates, a usually longitudinal row of cirral pairs in a zig-zag arrangement ±along the median of a cell.
mitochondrion: a cylindrical, subcellular organelle found in eukaryotes, containing some DNA and the enzymes required for metabolic processes. pl. mitochondria.
mixotroph (-y): an autotrophic organism taking up organic substances for supplementary nutrition (e.g. by phagotrophy), or a heterotroph with ingested chloroplasts supplementing nutrition. adj. mixotrophic.
monad: the flagellated stage in the life cycle of protozoa and algae.
monokinetid: of ciliates, the derived formation of unpaired individual kinetids.
monostromatic: single-layered, usually only one cell thick.
morphotype: an organism with a variation in form or structure from the type specimen, but considered to be circumscribed within the same species.
motile: moving, e.g. by swimming, gliding, crawling, kicking or pulsating.
mucocyst: of ciliates, a type of extrusome, mucilaginous, with a protective function against (for example) toxins, and possibly involved in cyst formation.
murolith: a heterococcolith with an elevated rim but without a well-developed shield, e.g. Syracosphaera pulchra.
naked: uncovered, e.g. a choanoflagellate or ciliate without a lorica, a dinoflagellate without thecal plates, or an amoeba without a test.
nanometre: a unit of length equivalent to 10–9 of a metre. abbrev. nm.
nanoplankton: plankton organisms in the size range 2–20 µm. adj. nanoplanktonic.
narrow girdle view: a frustule seen from the narrow side.
nematodesma (= cytopharyngeal rod): of ciliates, a rod-like, microtubular bundle arising from the distal side of neighbouring kinetosomes and cross-linked, often in a hexagonal pattern. pl. nematodesmata.
nematocyst: of dinoflagellates, an ejectile organelle, often arranged radially or subradially in the cell (e.g. in Polykrikos).
nilas ice: a very thin, grey, elastic type of ice with a matt surface which is readily bent by wave action.
non-ciliferous: without cilia.
non-contractile: not able to contract.
non-motile: not moving.
nucleolus: an organelle, containing rRNA, within a eukaryotic nucleus.
nucleus: a membrane-bound organelle in eukaryotic cells containing the chromosomes whose genes control the structure of proteins within the cell.
nuclear dualism: of ciliates, the simultaneous presence of somatic (macro-) and generative (micro-) nuclei within a cell.
ocellus: of diatoms, a small, siliceous thickening in the valve wall, usually with a thickened, structureless rim surrounding an area of small pores (e.g. in Eucampia); of dinoflagellates, a modified region of the chloroplast resembling a light-perceiving organelle, typically located in the left side of the cell.
occluded process: of diatoms, Family Thalassiosiraceae, a hollow, external tube not penetrating the valve wall, sometimes at the top of an areola.
operculate strutted process: of diatoms, Family Thalassiosiraceae, a strutted process penetrating a diatom valve, but which also has a small covering, or operculum, occluding the satellite pores around the base of each process.
oral cone: of ciliates,an everted, cytopharyngeal apparatus at anterior the end of a cell body.
otarium (= wing): of diatoms, Family Rhizosoleniaceae, one of a pair of membranous costae that occur opposite each other at or near the base of the external process. pl. otaria.
palmella stage: of haptophytes, Order Prymnesiales, a stage during which flagella are discarded, and cells proliferate within a mucilaginous matrix. adj. palmelloid.
papilla: a small projection from the surface. adj. papillate.
pappolith: of coccolithophores, a heterococcolith with a rim in the form of a narrow, slightly flanged wall composed of elements of two alternating type, one relatively small and confined to the proximal part of the wall, and the other vertically expanded, e.g. in Papposphaera spp.
paracingulum: a cingular area in dinoflagellate cysts.
parietal: borne or located on the wall.
paroral: of ciliates, at or along the right side of the buccal cavity. Also used as a noun for paroral membrane, i.e. a ciliary organelle lying along the right side of the buccal cavity.
pedicel: a type of holdfast organelle.
peduncle: a cytoplasmic appendage located near flagellar pores in some photosynthetic and non-photosynthetic dinoflagellates, associated with phagotrophy.
pellicle: a rigid or semi-rigid investment of some dinoflagellates and all ciliates. adj. pellicular.
peniculus: a type of ciliary membranelle positioned along the left wall in the buccal cavity of some oligohymenophorean ciliates. pl. peniculi.
pennate: referring to diatoms of the Order Pennales.
perioral: around the oral area.
peristomial field: of ciliates, generally refers to the entire, expansive, “everted” oral area with its encircling adoral zone of membranelles, etc.
peritrich: Subclass Peritrichia of Class Oligohymenophorea, a type of ciliate which, in the adult stage, has a characteristically inverted bell- or goblet-shaped or conical-cylindrical body, a conspicuous buccal ciliature at the apical pole, the somatic ciliature reduced to a subequatorial band and often a stalk (contractile or acontractile) or adhesive disc at the antapical pole; many species are sedentary (Order Sessilida) and form colonies.
pexicyst: of ciliates, Family Didiniidae, a type of toxicyst-like extrusome which, on discharge, adheres to the surface of prey without subsequent penetration.
petaloid: resembling the petal of a flower.
phagocytosis: ingestion of particulate food.
phagotroph (-y): any heterotrophic organism that ingests or absorbs nutrients as solid particles from its surroundings. adj. phagotrophic.
pharyngeal basket: of ciliates, a tubular cytopharyngeal apparatus, often curved, with walls strengthened by longitudinally arranged nematodesmata. Depending on the origin of the microtubules, a cyrtos- or rhabdos-type can be distinguished.
pharyngeal plug (= oral bulge): of ciliates, a ±bulge-like structure on the apical cell pole in the centre of which lies the cytostome.
phytoflagellate: a photosynthetic, flagellated organism.
phytoplankton: that part of the plankton made up of autotrophic organisms.
picoplankton: plankton organisms in the size range 0.2–2 µm. adj. picoplanktonic.
pigment: coloured material in organisms, often associated with photosynthesis.
pinocytosis: of dinoflagellates, the active engulfing of small particles or liquids from prey cells.
placolith: of coccolithophores, a heterococcolith composed of an upper and lower shield of radial elements, interconnected by a central column, e.g. in Calcidiscus leptoporus.
plankton: organisms drifting with the current, generally inhabiting the water column of an ocean, sea or lake; many planktonic organisms are capable of locomotion but are not sufficiently strong swimmers to move against the current. adj. planktonic.
pore/poroid: of diatoms and dinoflagellates, an opening or channel in a theca or cell wall.
poroid areola: of diatoms, an areola not markedly constricted at one surface of the valve.
posterior: that part of the organism which proceeds last in forward movement.
postmedian cingulum: of dinoflagellates, a cingulum located below the midpoint of the cell.
ppm: parts per million.
precyst: of testate amoebae, a short-term, dormant stage in the life cycle, enclosed by a relatively thin membrane (not a cyst wall), and with an internal diaphragm closing the aperture of the test.
prasinophyte: a member of the Class Prasinophyceae.
premedian cingulum: of dinoflagellates, a cingulum located above the midpoint of the cell.
preoral: of ciliates, anterior to the cytostome.
pretransverse cirri: of spirotrich ciliates, usually few ventral cirri immediately anterior to the larger transverse cirri.
proboscis: of diatoms, Family Rhizosoleniaceae, a permanent, elongate part of the valve with a truncate tip, considerably thicker than a flagellum (e.g. in Proboscia); the distal part fits into a groove on the adjacent valve of linked cells; of ciliates, Family Didiniidae, see oral cone.
process: of diatoms, a homogeneously silicified projection of a cell wall; in Family Rhizosoleniaceae, the process is spine-like.
prolate: lengthened, drawn out towards the poles.
protargol: protein silver impregnation of ciliates to stain the infraciliature (mainly kinetosomes, occasionally fibres), often nuclei and sometimes extrusomes, used to identify the ciliary structures.
protist: a member of the Kingdom Protista.
protoplasm: the living contents of a cell, i.e. the cytoplasm and nucleus. adj. protoplasmic.
protoplast: the main constituents of a cell; a cell excluding the cell wall.
protozoa: members of the Phylum Protozoa, a term widely used to refer to heterotrophic flagellates, ciliates and amoebae.
pseudocellus: of diatoms, Family Eupodiscaceae, an area of small, unoccluded pores at the cell apices which grade into the areolae on the valve face. cf. ocellus.
pseudonodulus: of diatoms, a solitary, marginal or submarginal structure evident as an open hole or an area covered by densely packed smaller areolae by LM. The principle diagnostic feature of Family Hemidiscaceae.
pseudopod/pseudopodium/pseudopodial projections: of Class Heliozea, and also of amoebae, temporary extensions of the cell surface without defined shape, functioning in locomotion and/or food uptake.
pseudostome: of testate amoebae, an aperture in the test through which the pseudopodia protrude.
ptychocyliform: of tintinnid ciliates, lorica shape as in genus Ptychocylis.
punctate: dotted, marked with dots. n. puncta; pl. punctae.
pyrenoid: a region of the chloroplast involved in starch formation in certain protists.
raphe canal: of diatoms, Family Bacillariaceae, a space on the inner side of the raphe cut off from the rest of the interior of the frustule.
raphe fins: of diatoms, Family Naviculaceae, small, paired, external, vane-like (or blade- or plate-like) siliceous structures arising from the raphe sternum.
raphe fissure: of diatoms, a narrowing opening of the raphe slit; terminal fissures at the valve ends can be hooked, Y- or T-shaped.
raphe keel: of diatoms, Family Naviculaceae, an elevation of the valve which bears and raises the raphe; also possessing specialised supporting structures (fibulae).
raphe slit: of diatoms, a longitudinal slit in the valve of some pennate diatoms, typically along or near the midline of the valve.
raphe valve: of diatoms, Order Pennales, the valve bearing the raphe.
reticulum: a network. adj. reticulate.
rhabdos: of ciliates, a type of tubular cytopharyngeal apparatus; not curved, may be eversible, with walls strengthened by longitudinally arranged nematodesmata. Derived from circumoral kinetosomes and lined with extensions of transverse microtubules; often contains toxicysts.
rhombic (-oid): having the shape of an oblique, equilateral parallelogram.
ribs: of dinoflagellates, Family Protoperidiniaceae, supports for sulcal or cingular lists.
ribbons: of diatoms, cells joined by abutting valve faces (Fragilariopsis) or by marginal linking spines (Synedropsis).
right: right-hand (view or side) in relation to the dorsal surface.
rota: of diatoms, a solid disc attached by spokes to the surrounding silica framework of a velum. pl. rotae.
rRNA: ribosomal RNA (ribonucleic acid), a nucleic acid within the cells of living organisms that is a vital component of protein synthesis.
saprobe: an organism that feeds on soluble organic nutrients of dead or dying plants or animals. adj. saprobic.
satellite pores: of diatoms, Family Thalassiosiraceae, small pores associated with strutted processes, penetrating a diatom valve; pores are sometimes occluded by an operculum (operculate strutted process).
scale: a calcified or silicified, plate-like outgrowth.
scutica: of ciliates, Subclass Scuticociliatia of Class Oligohymenophorea,usually a small, hook-like or whiplash group of often non-ciliferous kinetosomes posterior to the oral apparatus; during cell division, part of the new oral structures develops from this.
segment (= band): of diatoms, a single element of the girdle.
SEM: scanning electron microscope/microscopy.
septum: of diatoms, a sheet or ridge in the valvar plane projecting from a girdle band into the interior of the frustule, often with several openings.
seta: a hollow, bristle-like structure, often chitinous (in e.g. Chaetoceros). pl. setae.
sessile: fixed to a substratum, e.g. by a stalk or lorica.
sexual reproduction: involving the production of haploid gametes that fuse to produce a diploid zygote.
sheath: a loose covering, usually of mucus (as in the lorica sheath of Acanthocorbis unguiculata).
sigmoid: curved like the letter S.
siliceous: of, relating to, or incorporating silica.
silicoflagellate: a member of the Class Dictyophyceae.
silverline system: of ciliates, the entire system of pellicular or cortical structures, organelles or markings that can be revealed by silver nitrate impregnation; often, however, referring only to the striated or reticulate system of ‘lines’ (fibres); structures are possibly involved in morphogenesis or conduction of stimuli.
skeleton: any structure in an organism that maintains its shape and supports the structures associated with the body, e.g. silicoflagellates have a siliceous skeleton.
somatic: relating to the body surface, or to non-reproductive structures or activities; in ciliates, relating to all parts of the body not associated with the oral structures.
spathulate: spoon-shaped; broad at the tip and narrowed towards the base.
spicule: a delicate, pointed structure external to the cell, invariably excreted by the cell; more delicate than a spine.
spine: a solid protuberance or sharp, pointed structure, either part of a cell or secreted by it.
spine scale: a plate-like, secreted structure with a spine-like protrusion, usually siliceous.
spinule: a small spine.
spore: usually, a drought-resistant propagule and infection-inducing stage in the life cycle of several parasitic protozoa.
stepped chains: of diatoms, chains with overlapping cell ends (as in Pseudonitzschia).
sternum: see raphe sternum.
stigma: of diatoms, an isolated pore, typically in the central area of a valve face.
stria: of diatoms, surface ornamentation of areolae, pores of an alveolus appearing as lines or ridges. Orientation of striae is useful in identification, e.g. parallel, radiating, linear or convergent. pl. striae; adj. striate.
strutted process: of diatoms, Family Thalassiosiraceae, a tubular process penetrating a diatom valve, through which a thread of organic material (mostly chitin) is extruded; see trifultate strutted process; cf. occluded process.
stylus (= podite): of ciliates, Class Phyllopharyngea, a conical, foot-like appendage projecting from the posterior ventral surface, through which a mucus-like filament can be secreted for temporary attachment to a substratum.
subpellicular platelet layer: of strombidiid ciliates, a rigid layer of small, polygonal polysaccharide plaques (skeletal elements) subpellicularly in the posterior portion (often half) of a cell.
suctoria: of ciliates, Subclass Suctoria of Class Phyllopharyngea, a type of ciliate which, in the adult stage, is generally sedentary, lacks cilia, feeds by means of suctorial tentacles, and often has a non-contractile stalk; in the swarmer stage, is ciliferous and mobile.
sulcus: a longitudinal area on the ventral surface of a dinoflagellate cell that forms the furrow housing the longitudinal flagellum.
suture: of dinoflagellates, a visible, linear boundary between thecal plates.
swarmer: a freely motile dispersal stage in the life cycle of a number of sessile ciliates (e.g. suctorians, peritrichs).
symbiont: an organism living in a state of symbiosis with another, a relationship in which both partners benefit.
synhymenium: of nassophorid ciliates, a hypostomial flange, perioral ciliature; a band of ciliature (‘membrane’) slightly posterior to oral area, ±traversing helically the ventral side and sometimes extending to the dorsal side, composed of closely set kinetal segments (mono-, di- or polykinetids).
systematics: the area of biology dealing with the classification, naming (nomenclature) and evolution of organisms.
TEM: transmission electron microscope/microscopy.
tentacle: of suctorians, a long, tubular cell projection, usually stiffened by microtubular bundles and equipped with haptocysts at the tip, extensible and retractable, used in prey capture and food uptake.
terminal nodule: of diatoms, Family Bacillariaceae, a thickening at the apical end of the raphe.
terminal seta: of diatoms, a seta on the end valves of a chain.
test: a general term for a rigid shell or lorica around an organism. adj. testate.
theca: an extracellular covering, e.g. test, valve or frustule, enclosing a cell. pl. thecae.
thecal plates: plates of armoured dinoflagellates composed of cellulose or other polysaccharide microfibrils.
thecostyle: of suctorian ciliates, a posterior, stalk-like extension of the lorica.
thigmotactic: of ciliates, adhering; also referring to specialised, somatic cilia that are modified to serve a tactile or adhering function.
thylakoid: a thin-layered plate within a chloroplast.
toxicyst: of ciliates, a type of toxic extrusome, used in prey capture.
transapical plane: perpendicular to the transapical axis.
transverse cirri: of spirotrich ciliates, a group of often enlarged cirri in the posterior quarter of a cell, frequently in an oblique, J-shaped row.
trichocyst: of dinoflagellates and ciliates, an ejectile organelle.
trichocyst pore: of dinoflagellates, an opening or channel in the theca, possibly involved in pinocytosis, extrusion of trichocysts and mucocysts and other active processes.
trifultate strutted process: of diatoms, Family Thalassiosiraceae, a strutted process, penetrating a diatom valve, with a long internal tube with three columnar supports.
triradiate: radiating in three directions.
triundulate: with three undulations or bulges.
trochospiral: of foraminiferans, relating to chambers that are spirally coiled.
trophont: of ciliates, an adult trophic and growing stage of the life cycle.
truncate: ending abruptly, as if cut off.
tubular process: of diatoms,a simple tube penetrating the valve wall.
tychopelagic: of diatoms, relating to the bottom of a substratum, e.g. ice, until detached into the surrounding water.
umbilicus: of foraminiferans, having a small, central depression or hollow. adj. umbilicate.
unarmoured (= naked, athecate): of dinoflagellates, cells without an identifiable theca or cell wall; while they do not have apical pore complexes, there may be an apical groove. Some species with thin thecal plates and apical grooves are considered to be transitional between unarmoured and armoured cells.
vacuole: a membrane-enclosed compartment in the cell, e.g. food vacuole, contractile vacuole.
valvar plane: a plane of division parallel to the valve surface.
valve: two opposing halves of theca or test.
valve face: the entire diatom valve surface, surrounded by the mantle.
valve mantle: marginal parts of a diatom valve, set off from the valve face at an angle.
valve view: a diatom frustule seen from top or bottom.
valvocopula: of diatoms, an intercalary girdle band adjacent to a valve.
varimorphic: coccoliths on a coccosphere showing a continuous range of morphology between two end member morphologies, e.g. in Papposphaera borealis.
velum: of diatoms, a thin, perforated layer of silica across an areola; of dinoflagellates, a flat, cellular projection, especially in heterotrophic dinoflagellates, involved in locomotion and food uptake.
ventral: the underside of an organism; in dinoflagellates, the ventral side is identified by the presence of the sulcus; in ciliates, by the position of the cytostome, except when this is apical, then opposite to brosse (exception: suctorians); in testate amoebae, by the position of the pseudostome.
ventral ridge (= ventral flange): of dinoflagellates, an identifiable ridge on the right side of the sulcal intrusion onto the epitheca.
vermiculate: with raised, worm-like markings, e.g. on the thecal plates of armoured dinoflagellates.
zig-zag or stellate colonies: of diatoms, cells joined in star-shaped colonies by mucilage pads (e.g. in Thalassionema).
zooid: of dinoflagellates and ciliates, a motile cell or body produced by an organism or individual member in a colony.