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Soft-Bodied Stream Algae of California


Glossary of Terms




akinete thick-walled cell produced by members of several algal classes; may be released by vegetative cells; functions as an asexual resting stage and typically is resistant to harsh conditions

amorphous without a definite shape

antheridium (pl. antheridia) male gametangium in a wide variety of algal groups

anterior in front, towards the front, or the opposite of posterior; also the direction of movement of many flagellated cells

apical cell cell positioned at the front end of a filament or thallus; often the site of meritematic growth

aplanospore nonmotile (nonflagellated) spore produced by cell divisions of parental cell; may have the potential to produce flagella in some groups

arcuate arched or crescent shaped; in diatoms, pinnate cells that are bent along the apical axis

autospore nonflagellated spore similar in appearance to the vegetative cell that produced it



basal toward or at the base of a thallus or filament



caespitose clustered, in thick tufts or clumps, forming a turf

calcification process of depositing calcium carbonate, which occurs on algal cell surfaces or in walls, especially in alkaline habitats

carpogonial branch supports the female gametangium (carpogonium) in the red algae; usually differentiated from surrounding vegetative cells

carpogonium female gametangium in red algae, usually consisting of the receptive region (trichogyne) for the male gamete (spermatium) and a nucleated base

carposporangium sporangium of many red algae that typically forms diploid spores (carpospores) on tips of the postfertilization stage (carposporaphyte). Carpospores usually germinate into free-living diploid phase of the life history

carposporophyte postfertilization stage of many red algae, typically consisting of small diploid filaments (gonimoblast) attached to the haploid gametophyte. Gonimoblast filaments form diploid spores (carpospores) at their apices

cell wall typically rigid external structure enclosing the cell membrane; may consist of cellulose, silica, pectin, or other materials

chantransia stage diploid life-history phase of members of the red algal order Batrachospermales and Balbianiales. Forms the haploid gametophyte stage directly attached to it by meiosis of an apical cell

chloroplast membrane-bound organelle that contains photosynthetic thylakoids, chlorophyll-a, and other pigments (also called “plastid”)

chromatoplasm portion of a cell that contains pigments; in cyanobacteria, typically a peripheral pigmented region

clathrate with irregular perforations or openings; lattice-like

coccoid simple cell type that is spherical, subspherical, or rod-shaped

coenobium (pl. coenobia) form of colony in which the number of cells is fixed (genetically determined) at an early developmental stage and passes on to the next generation

coenocytic multinucleate condition and lacking cross walls between nuclei; some coenocytic taxa produce cross walls during reproduction (e.g., Vaucheria)

colony group of cells that may be connected or held together by cytoplasmic strands, mucilage, or parent cell wall

confluent growing together or intermingled; sheaths or walls that join together

conjugation form of sexual reproduction in which nonflagellated gametes join sometimes by specialized tube or papillae (e.g., Zygnemataceae)

contractile vacuole membrane-bound vesicle that expands and contracts to regulate water and/or osmotic conditions within cells; especially in non walled forms

cortex peripheral layer of cell in a differentiated thallus that is typically photosynthetic and surrounds the inner colorless medulla

cortical filament filament that is that is part of a surrounding layer that covers the main axis of the thallus (e.g., red algae and charophytes)

corticated thallus possessing cortical filaments or cells

cyst nonmotile thick-walled stage that protects the alga during adverse conditions; also termed resisting cyst



daughter cells cells derived from a parent by a mitotic division

distal away from the base or center of a thallus or filament (opposite of basal)

dorsal the upper surface in dorsiventral cells

dorsiventral with distinct front (ventral) and back (dorsal) sides that are often concave and convex



endospore (baeocytes) spores produced by certain cyanobacteria or green algae via repeated (often rapid) divisions of vegetative cells, yielding smaller daughter cells in the original cell

exospore (pl. exocyte) in cyanobacteria, daughter cells that divide externally from distinctly polarized cells (e.g., Chamaesiphon); produced singly or successively in rows.

eyespot (stigma) light sensitive, typically orange to red-colored (carotenoids pigments) spot in many algal cells (typically flagellates or motile reproductive stages of multicellular forms), and typically in the anterior region of the cell



false branching (pseudobranching) condition where branches arise from a break in the main filament and the continued growth of one or both ends; in cyanobacteria only the sheath splits while the vegetative trichomes separate

fasciculate occurring in bundles, as clusters of filamentous cyanobacteria, elongated cells in green algae, or the striae on the diatom

filament common type of thallus in which cells are arranged in a linear series and in which adjacent cells share a common cross wall

flagellate cells that posses one or more flagella

flagellum (pl. flagella) long, threadlike organelle that projects out of the cell and functions in motility; in eukaryotic cells, they consist of a 9 doublet + 2 central singlet array of microtubules

fusiform spindle-shaped; any elongate morphology that is widest near the middle and tapering at either end

furrow a longitudinal depression or deep striation



gametangium (pl. gametangia) any structure of a thallus that produces gametes

gametophyte multicellular, usually haploid, gamete-producing stage in organisms that exhibit alternation of generations

gas vesicles gas containing spherical or cylindrical structure in cyanobacterial cells, often in clusters termed aerotopes (the older term is gas vacuoles) and visible with light microscopy as red or brownish bodies (due to refraction of light). Function to provide buoyancy to planktonic forms (e.g., Microcystis, Anabaena)

geniculate having joints like a knee; occurs in some filamentous green algae (e.g., Klebsormidium, Zygnema)

globose in the form of a globe; completely or nearly spherical

gonimoblast filament in red algae, a diploid filament that composes the postfertilization stage (carposporophyte) and is localized on the haploid gametophyte. Diploid spores (carpospores) are formed at filament tips



hair cell typically colorless, thin, and elongate cell at branch apices that increases the thallus surface area for nutrient and gas exchange; in some filamentous cyanobacteria, green algae and red algae, produced in response to nutrient deficiency

heterocyst (heterocyte) in certain cyanobacteria (e.g., Anabaena, Nostoc, and Calothrix), a thick-walled, multilayered (apparently anaerobic), and weakly pigmented cell; contains the nitrogenase enzyme, which enables fixation of gaseous nitrogen (N2) to ammonium

heteropolar cell or filament with both poles different in structure and/or function

holdfast unicellular or multicellular structure that attaches a thallus to the substratum

hormogonium (pl. hormogonia) in filamentous cyanobacteria, a means of vegetative reproduction (and dispersal) formed via fragmentation of the trichome, forming distinct segments that are often motile (via gliding)

hyaline transparent or colorless



isodiametric diameters equal; in filamentous forms, the diameter is more or less constant along its length

isopolar cell or filament with both poles similar

isthmus in desmids, the constriction between semicells; typically the location of the nucleus



keritomy irregular to radial arrangement of thylakoidal, sometimes with intra-thylakoidal spaces, e.g., keritomized chromatoplasm in cyanobacteria Cyanothece, Tychonema



lamellate layered or arranged in layers

lanceolate shape that is wider near the center than the ends

lateral conjugation in members of Zygnemataceae conjugation that occurs between two adjacent cells on the same filament

lenticular lenslike or lentil shaped; flattened or thinning toward the ends

linear morphologies with generally parallel sides

lorica protective layer or envelope that surrounds the protoplast, but typically not attached to it (naked, nonwalled, cell); present in genera from from several flagellate groups (e.g., Trachelomonas)



macrandrous sexual reproduction where the male filament is as large as the female thallus and with small antheridia (e.g., species of Oedogonium and Bulbochaete)

metaboly cell shape shifting (e.g., Euglena)

moniliform filamentous morphology that looks like a string of beads

monoecious literally, one household; organisms in which male and female gametes are produced on the same thallus



nannandrous in some species of green algae (e.g., within Oedogonium), a very small (often unicellular) male filament that attaches to a much larger female filament



obovoid inversely ovoid, with the broader end upward or outward; also termed obovate

oogonium (oogonia) large, single-celled female gametangium that may produce one or more eggs

ovoid egg shaped; rounded with inner pole or downward broader than the other



palmelloid a nonmotile, colonial stage of indefinite cell number and arrangement; often within a mucilaginouis matrix in many algal groups

papilla protuberance or swelling

pellicile in some dinoflagellates, layer beneath the amphiesmal vesicles which remains upon ecdysis of outer layers. In euglenoids, the outer proteinaceous surface layer, often in a helical arrangement

posterior located towards the back or the opposite of anterior

pseudofilament loose chain of cells held together with a common gelatinous matrix, or linked by fibrils or other connections; cells are typically separated from each other. Unlike true filaments, they do not share a common cross wall

pseudocilium (pl. pseudocilia) hair-like extensions in certain green algae (Tetrasporales) that are similar to flagella in shape but not used for locomotion

pyrenoid distinct, proteinaceous structure (often spherical), embedded in or associated with chloroplasts of algae; in some, contains the enzyme RuBisCO; associated with starch in green algae

pyriform pear shaped



quadrate square or rectangular



reniform bean- or kidney- shaped

replicate folded back

reticulate netlike or arranged to form a network

rhizoid downward-growing cell or chain of cells that is typically involved in thallus attachment to substrata



saccate like a sac or balloon

scalariform conjugation a type of conjugation, where the conjugation tube forms between two parallel filaments, in members of the Zygnemataceae

scrobiculate surface pitted or furrowed; with many small depressions

sheath mucilaginous covering of cells, colonies, or filaments (trichomes); may be firm or loose, narrow or broad

siliceous composed primarily of silica (e. g. diatom frustules)

sinus constricted region in a cell; e. g. the median constriction in desmids

spermatangium in red algae, a male gametangium that is typically a colorless, obovoid cell produced at the tips of vegetative branches; each produces a single male gamete (spermatium) that is released to fertilize the female gametangium (carpogonium). Some form spermatangia on specialized stalk cells

spermatium colorless male (nonflagellated) gamete in red algae

sporangium (sporangia) structure that produces spores

spore specialized (asexual) reproductive structure that germinates without fusion into a new thallus

sporophyte typically diploid, spore-producing stage in an organisms that exhibit alternation of generations

stomatocyst (statospore) siliceous resting stage produced by several types of algae (e.g., Hydrurus and other Chrysophyceae)

stellate star shaped; describes several features of algal cells, such as chloroplasts or cell shape

subapical near the apex but not at the top of the thallus



thallus (pl. thalli) general form or body of an alga

trichogyne receptive portion of the female gametangium (carpogonium) of many red algae

tufts short radiating filaments without a common matrix (e. g., Audouinella)



ventral the lower surface in dorsiventral cells



whorl radiation type of branching that has several lateral filaments arising at a common position in the main axis



zoospore motile (flagellated) spore formed by vegetative cells or in specialized sporangia; typically the same ploidy as the parental cell

zygospore thick-walled resting cyst formed after fertilization of an oogonium or fusion of gametes