Hydrosera Guide
Credit: David Burge
  1. Valve margin appearing doubly triangular
  2. Porefields three, with pseudocelli
  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 pseudocelli, 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.