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Name derivation: |
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Classification: |
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Isthmia C.Agardh 1832, 4 of 36 species descriptions are currently accepted taxonomically (Guiry and Guiry 2013).Order Biddulphiales, Family Biddulphiaceae |
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Morphology: |
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Cells either rhomboidal or trapezoidal in girdle view and attached by massive mucilate pads to form complex branching colonies. Plastids discoid. Valves oval (bipolar) in valve view and with no distinction into valve face and mantle. Valves heteropolar, one pole being much more elevated than the other. Frustules slightly heterovalvate, one valve being produced into a more bulbous extension than the other and having a conspicuous pseudocellus at this pole. Valves with a massive siliceous framework more-or-less equally developed on both the outside and inside of the valve (I. enervis) or the internal framework enlarged in a 'girder-like' manner (I. nervosa). Areolae elliptical to polygonal, containing complex thick cribra. In addition simple pores penetrate the framework in various places (Guiry and Guiry 2013). |
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Habitat: |
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Cells epiphytic on seaweeds, e.g. species ofPolysiphonia, Ceramium, etc. (Guiry and Guiry 2013). |
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References: |
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Agardh, C.A. 1832. Conspectus Criticus Diatomacearum. Part 4. pp. 49-66. Lundae [Lund]: Literis Berlingianus. Guiry, M.D. and G.M. Guiry 2013. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway. http://www.algaebase.org; searched on 27 March 2013. |
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