From Frustule
| Epitheca, Epivalve |
The larger of two external siliceous valves that comprise a diatom skeleton (frustule). All diatom frustules are composed to two valves, the epitheca (upper valve) and the hypotheca (lower valve); each valve also has their own associated siliceous cingulum elements (epicingulum & hypocingulum, also collectively referred to as girdlebands). During asexual diatom reproduction, two new valves form within the cell, each paired with one valve of the parent cell; both internal valves are always smaller than the external valve they are paired with during reproduction, and thus both older valves become an epitheca on the new daughter cells when cell division is complete.
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References
- Barber, H.G. & Haworth, E.Y. 1981. A guide to the morphology of the diatom frustule. Freshwater Biological Association, Ambleside, Cumbria, UK. 112 pp.
- Round, F.E., Crawford, R.M. & Mann, D.G., 1990. The Diatoms: Biology and morphology of the genera. Cambridge: Cambridge University Press. 747 pp.
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External Links
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