LOGO River diatoms: a multiaccess key
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Glossary A

Alveoli
(plural) Elongate chambers in the surface of the valve. The top surface of these is composed of punctae or similar structures, which may only be resolvable under the electron microscope. Often appear as thick 'ribs' under the light microscope.


valve view brightfield

Alveolus
(sing.) See above


Apical symmetry
Symmetrical about the apical (longitudinal) plane of pennate diatoms. May be isopolar (e.g. Navicula) or heteropolar (e.g. Gomphonema).




Apiculate
Condition where end of valve is drawn out into a fine point. Cf rostrate, where the valve end is broader.



Araphid
Not bearing a


Areolae
(plural) Collective term for fine perforations (such as striae) on the surface of the valve.


Areola
(sing) see above


Autotroph
(n) Able to manufacture organic constituents from inorganic raw materials. Diatoms and other algae use sunlight as an energy source and chlorophyll as a catalyst for this process, although some species are also capable of heterotrophic nutrition under some circumstances.


Autotrophic
(adj) see above


Axial area
Area between the two rows of striae. May be narrow (e.g. Synedra ulna) or broad (e.g. Pseudostaurosira brevistriata) and is a useful diagnostic feature in some taxa. cf sternum.

See characters:
- Axial area, width


Comments to: Diatom Key Development Team