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Diatoms of the United States is now known as Diatoms of North America.
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Wallich 1858      Category: Centric
TYPE SPECIES: Hydrosera triquetra Wallich




Image Credit: David Burge

CLASS: Coscinodiscophyceae
  ORDER: Biddulphiales
    FAMILY: Biddulphiaceae

  1. Valve margin appearing doubly triangular
  2. Porefields three, with ocelli present, positioned on the ends of one of the "triangles"
  3. Rimoportula distinct

Hydrosera is a large multipolar, centric diatom. Frustules are heavily silicified. Valve margins appear to be in the shape of two superimposed triangles. A distinct rimoportula is present. Porefields, containing ocelli, are positioned at the three poles of one of the apparent triangles. Frustules form large zig-zag colonies, joined by mucilage secreted from the porefields.

Hydrosera grows in streams of southern coastal areas and tropical islands. The colonies are benthic and anchored to the substrate by attachment of the terminal cell.

Cite This Page:
Spaulding, S., and Edlund, M. (2008). Hydrosera. In Diatoms of the United States. Retrieved May 22, 2018, from

Contributor: Sarah Spaulding | Mark Edlund - December 2008
Reviewer: Sam Rushforth - June 2010