Cymbella C.Agardh, 1830, nom. et typ. cons.

Lectotype species: Cymbella cymbiformis C.Agardh

Original publication and holotype designation: Agardh, C.A. (1830). Conspectus criticus diatomacearum. Part 1. pp. 1-16. Lundae [Lund]: Literis Berlingianus.

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Description: Frustules in girdle view linear; in valve view lunate, semicircular or strongly naviculoid, but retaining at least some degree of dorsiventrality. The central portion of the valve may be clearly set off as a central area, may not be distinguished at all from the axial area, or may be merely a slight widening of the axial area. In the latter case it can be considered as an axio-central space. The axial area may be + straight or dorsally arched. The raphe, or at least some parts thereof, is commonly lateral except for some of the smaller forms where it is seen as filiform. A raphe slit which cuts through the valve ± perpendicular to the valve surface is considered in this treatment as a filiform raphe (about the same width, appearing relatively narrow). A raphe slit which cuts through the valve oblique to the valve surface is considered here as a lateral raphe (somewhat variable in width but broad or ribbon-like). Proximal and distal raphe ends, although sometimes difficult to see, are particularly noted because I believe their configuration to be rather stable for a given taxon. Central and terminal nodules of variable distinction are present. The plate illustrations, however, show only the more prominent nodules. Striae are either punctate or lineate and vary in direction from radiate to convergent. At some point above and below mid-valve the striae are at least somewhat radiate. Striae around the center are usually radiate, but can be parallel. Terminal striae can be radiate, parallel, or convergent. Somewhere in the central area there may be one to several "dots." subtile or quite distinct. Those which appear to have the same morphology as the subdivisions of the striae are termed "isolated puncta.” Those which are poroid and show striae are designated on either side of central either side of central area a different refraction than the puncta forming the as stigmata (stigma) (Cleve, 1894, p. 157). In some cases these are situated just off the end of a central stria and are easy to miss without careful focusing. In other cases they are quite distinct, often cutting through the valve at an angle (e.g., C. tumida). Frustules of Cymbella may grow individually and unattached, stalked (Cocconema) or in tubes (Encyonema). The more precise growth habit for many species of Cymbella and the capabilities for change in growth habit of individual species are yet to be thoroughly investigated.

Information contributed by: Patrick & Reimer (1975: 15-16).. The most recent alteration to this page was made on 2024-01-22 by M.D. Guiry.

Taxonomic status: This name is of an entity that is currently accepted taxonomically.

Gender: This genus name is currently treated as feminine.

Most recent taxonomic treatment adopted: Kociolek, J.P. & Spaulding, S.A. (2003). Eunotioid and Asymmetrical Naviculoid Diatoms. In: Freshwater Algae of North America, Ecology and Classification. (Wehr, J.D. & Sheath, R.G. Eds), pp. 655-668. San Diego: Academic Press.

Comments: Most taxa of this genus are restricted to fresh water. Of the species treated here, C. pusilia appears to be the only one capable of surviving, in relatively large numbers, in salt concentrations approaching that of sea water.

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Contributors
Some of the descriptions included in AlgaeBase were originally from the unpublished Encyclopedia of Algal Genera, organised in the 1990s by Dr Bruce Parker on behalf of the Phycological Society of America (PSA) and intended to be published in CD format. These AlgaeBase descriptions are now being continually updated, and each current contributor is identified above. The PSA and AlgaeBase warmly acknowledge the generosity of all past and present contributors and particularly the work of Dr Parker.

Descriptions of chrysophyte genera were subsequently published in J. Kristiansen & H.R. Preisig (eds.). 2001. Encyclopedia of Chrysophyte Genera. Bibliotheca Phycologica 110: 1-260.

Linking to this page: https://www.algaebase.org/search/genus/detail/?genus_id=43694

Citing AlgaeBase
Cite this record as:
M.D. Guiry in Guiry, M.D. & Guiry, G.M. 22 January 2024. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway. https://www.algaebase.org; searched on 21 November 2024