Glossary of Terms for Freshwater Algae
aerial Growing in a habitat above the ground or water
akinete A thick-walled spore that can survive harsh conditions and functions as an asexual resting stage
algaenans  Hydrocarbon polymers that help some algal cells resist decay
anisogamy  Sexual reproduction involving two types of gametes of different sizes or shapes
antheridium  A cell that produces male gametes
apical cell Cell located at the end of a filament or thallus
aplanospore A nonflagellate spore that may be genetically capable of producing flagellated cells under the right conditions; produced by divisions of the parent cell
araphid diatom Diatom lacking a raphe structure on either valve
areolae Pores or perforations in the siliceous valves of diatoms
asexual reproduction Reproduction involving the cells of a single parent
autocolony A miniature version of the parent colony produced asexually by one of its cells; a coenobium
autospore A nonflagellate spore
axial  A chloroplast located in the center of a cell along its longitudinal axis
basal Concerning the base of a thallus or filament
benthic Inhabiting the bottom of an aquatic environment
biflagellate Cells with two flagella
bloom  Visible or nuisance algal growth often associated with nutrient-rich conditions
blue-green algae See cyanobacteria
brackish Slightly salty waterbodies
calyptra Thickened or enlarged tip of a cyanobacterial filament
charophyceans or
charophyte green algae
The group of green algae most closely related to the land plants, includes the zygnematalean algae (Spirogyra and the desmids) as well as several other genera and the stoneworts
chlorophyll-a Primary photosynthetic pigment in algae and higher plants
chlorophyll-b Photosynthetic pigment found in higher plants, green algae, and some euglenoids
chlorophyll-c Photosynthetic pigment found in chrysophytes, synurophytes, diatoms, tribophytes, dinoflagellates, cryptophytes, and brown algae; includes c1 and c2 components
Green algae
chloroplast (plastid) Membrane-bound organelle involved in photosynthesis
chrysophytes Mixotrophic algae with golden-brown pigmentation
chytrids Group of small, colorless fungi that may parasitize algal cells 
chromatophore  An organelle that contains pigments; i.e. a plastid
cingulum (pl. cingula) In the dinoflagellates, a transverse groove that usually holds the transverse flagellum; another term for girdle band
coenobium (pl. coenobia) A type of colony with a genetically-predetermined morphology and number of cells; each cell of the parent colony can produce an autocolony that is an exact replica of the parent colony
coenocytic Multinucleate and lacking tranverse cell walls; siphonous
conjugation In the zygnematalean algae, sexual reproduction involving nonflagellate gametes that combine in a special tube or structure; see also lateral and scalariform conjugation
contractile vacuole A membrane-bound vesicle that expands and contracts to expel excess water
cross walls Transverse cell walls
cyanelles The blue-green plastids of the glaucophytes that originally resulted from an endosymbiotic event
cyanobacteria Photosynthetic bacteria with a characteristic blue-green color, commonly known as the blue-green algae
cytokinesis  Division of the cytoplasm during cell division
desmid A group of unicellular or filamentous green algae; see also placoderm desmids and saccoderm desmids
detritus Dead or decaying organic matter
diatoms Photosynthetic microalgae with siliceous cell walls
dioceious Organisms in which male and female (or + and -) gametes are produced on different individuals 
dinoflagellates  Unicellular algae that are often covered in thick, armoured plates
double false branching  Growth pattern that occurs when a filament breaks apart (often at a dead cell or heterocyst) and both pieces emerge through the mucilage sheath and continue to grow
embryophytes The group consisting of bryophytes and vascular plants 
endosymbiont An organism that lives inside another, benefitting both individuals
epilithic  Growing on the surface of rock or stone
epiphytic Growing on the surface of plants or other algae
eutrophic Waters rich in dissolved nutrients (especially nitrogen and phosphorus); leads to accelerated growth of algae and plants that depletes oxygen levels and reduces biodiversity
euglenoids  Organisms that are unicellular or colonial, colorless or pigmented, and may move with an undulating, shape-changing motion (see metaboly)
eyespot A light-sensitive, red-pigmented spot usually found in the cell anterior of some flagellated algal cells or reproductive cells; sometimes called a stigma  
false branching Single false branching occurs when a filament breaks apart (often at a dead cell or heterocyst) and one piece emerges through the mucilage sheath and continues to grow; see also double false branching
flagellum (pl. flagella) A long, whiplike organelle that usually protrudes from a cell and is used for motility
fragmentation  Type of asexual reproduction where the parent thallus breaks into pieces to form new individuals; may be accidental or genetically programmed
frustule The siliceous components of a diatom cell; i.e. the valves and girdle bands
fucoxanthin A brown carotenoid pigment used in photosynthetis, found in the golden-brown and brown algae
gametes Reproductive cells
gas vesicles In cyanobacteria, cylindrical structures used to increase cell bouyancy
gas vacuoles Sometimes synonymous with gas vesicles, also refers to a group of gas vesicles
girdle band or
cingulum (pl. cingula)
In diatoms, the rings or bands of silica encircling the valves where they overlap.
In desmids, the short wall segments oriented transversely at the central portion of the cell
glaucophytes  A group of algae that contain blue-green plastids called cyanelles, sometimes called Glaucocystophytes
golden-brown algae Algal groups with golden pigmentation; i.e. the chrysophytes, synurophytes, haptophytes, and diatoms
gone In the desmids, a cell derived from zygote germination that may not have the typical morphology of that species
grana (pl.) Stacks of thylakoids found in the discoid chloroplasts of land plants and some green algae
green algae Morphologically diverse group of algae with green-pigmented chloroplasts
hair cells Elongate, usually colorless cells or extensions of cells found at branch apices, increases surface area for nutrient and gas exchange and may protect the cells from herbivory
halophilic Inhabiting a salty environment
haploid Having a single set of chromosomes
heterocyst In some cyanobacteria, a large, thick-walled cell involved in nitrogen fixation
heteropolar Filaments with distinct basal and apical components or cells that are assymetrical along the transverse axis 
heterotrophic Organisms that feed on organic matter from external sources, and are osmotrophic or phagotrophic
holdfast cells Structure that attaches a thallus or filament to the substrate
(pl. hormogonia)
In filamentous cyanobacteria, short, usually motile segments that break off from the main filament and are used for asexual reproduction and dispersal
hypnospore A thick-walled resting cyst 
hypnozygote A thick-walled, nonmotile resting zygote that remains dormant for a period of time until germinating when conditions improve; found in green algae, dinoflagellates, and some other flagellated organisms
intercalary Located in the middle of a thallus, not on the end
isogamy Sexual reproduction involving two types of gametes that function differently but are morphologically identical
isopolar Symmetrical along the tranverse axis, having the same morphology at both ends
isthmus In desmids, the constricted region between the two semicells that usually contains the nucleus 
lateral conjugation  Conjugation where two cells on the same filament reproduce within a conjugation tube
littoral zone Region near the shore of lakes, ponds, or large rivers
lorica A protective covering surrounding flagellated cells of some algal groups
meristem Portion of a thallus where the cells are able to divide and produce new growth
metaboly Shape-changing motion of the euglenoid genera that does not involve flagellar movements 
metaphytic Growing among the floating microscopic community in the littoral zone that is often associated with aquatic plants
mixotrophic Cells with both photosynthetic and heterotrophic or phagotrophic nutrition
monoecious  Organisms in which male and female (or + and -) gametes are produced on the same individual
monophyletic A group of organisms that share a single common ancestor
multicellular Composed of more than one cell
multinucleate Having many nuclei
necridic cells (necridia) Dead cells in cyanobacteria that disrupt the main filament to produce false branching or hormogonia
oligotrophic Waters low in nutrients and organic production, typically rich in biodiversity
oogamy Sexual reproduction involving the fusion of a small, flagellated male gamete with a larger, nonflagellated female gamete
oogonium (pl. oogonia) A female reproductive structure capable of producing one or more eggs
osmotrophic Organisms that feed on dissolved organic molecules absorbed from the outside environment
parietal Near the outer or peripheral surface of a cell or thallus; commonly used to describe chloroplasts situated along the cell wall 
pellicle The surface covering of euglenoid cells composed of proteinaceous strips in a helical pattern
periphytic Growing attached on the surfaces of plants, other algae, or other substrates
phagotrophic Organisms that feed by ingesting particulate organic carbon or intact cells
phototaxis Movement in response to light
photosynthetic Organisms that use sunlight as an energy source to synthesize carbohydrates from carbon dioxide and water
phylogenetic Concerning the relationships of evolutionary development
phytoplankton Floating or swimming microscopic algae and cyanobacteria 
placoderm desmids Unicellular or pseudofilamentous desmids with cell walls made up of two parts of different ages separated by a central isthmus that are covered in pores
plastid See chloroplast
polar nodule  In cyanobacteria, thickened regions where the heterocyst cell wall attaches to a vegetative cell
polyeders In Hydrodictyon and Pediastrum, polygonal cells produced from zygote germination that give rise to new coenobia
polyphyletic A group of organisms descended from more than one ancestor, may be more closely related to other organisms outside of the taxonomic group
protoplasm, protoplast The living substance of a cell
pseudofilament Loose chain of individual cells held together by mucilage or attached at the end walls, rather than sharing a common cell wall as in a true filament
pyrenoid A proteinaceous structure associated with algal chloroplasts that often forms storage compounds
quadriflagellate Cells with four flagella 
raphe  In diatoms, a slit in the valve face that allows the cell to move along a substrate
rhizoid Rootlike extensions usually used to attach a thallus to the substrate 
saccoderm desmids Desmids with a homogeneous cell wall that lacks pores; are not differentiated into two semi-cells
scalariform conjugation  Conjugation involving two filaments that allign laterally and form conjugation tubes between adjacent cells in a ladder-like arrangement
semicell  In placoderm desmids, one-half of a cell 
sexual reproduction Reproduction involving the cells of a single parent
silica deposition vesicle Involved in the formation of the siliceous valves of diatoms and siliceous scales of chrysophytes and synurophytes
siphonous See coenocytic
striae  Term used to described elongated markings on the cell walls of desmids and diatoms
subaerial Growing on or near the earth's surface
sulcus In dinoflagellates, a longitudinal groove in the ventral side of the cell that holds the longitudinal flagellum  
suture In dinoflagellates, the regions between thecal plates
syngamy The fusion of two gametes during fertilization
Motile flagellates covered by siliceous scales; the scaled chrysophytes
terminal  Located at the end of a thallus
thallus General form of an alga that, unlike a plant, is not differentiated into stems, roots, or leaves
thylakoid Flattened membranous sacs that form the chloroplast membranes
tribophyte algae See yellow-green algae
trichome A filament of a blue-green alga or cyanobacterium
trichogyne In some charophycean green algae and in the red algae, the elongated portion of the female reproductive structure that recieves the male gametes
turbidity Measure of the cloudiness of a waterbody due to suspended particles
unicellular Composed of a single cell
uniseriate Composed of a single row of cells.
valve  In the diatoms, the two siliceous halves of the cell wall
vegetative cells Cells involved in growth, nutrition, or asexual reproduction, but not sexual reproduction
vesicles  SDV, gas
yellow-green algae  Rare algae with yellow-green pigmentation; the tribophyte algae
zoospore A flagellated spore 
zygospore A thick-walled resting spore formed from the fusion of gametes or a fertilized oogonium
zygote The cell resulting from the fusion of two gametes