Setae
Setae are simple or robust extensions of the diatom valve. They are more elongate than spines and found in the genera Chaetoceros and Bacteriastrum. Setae function to join frustules together to form chains and maintain buoyancy of colonies in a planktonic environment.
Citations
Barber, H.G. and Hayworth, E.Y. (1981). Guide to the Morphology of the Diatom Frustule. Freshwater Biological Association, 112 pp.
Image Credit: Sarah Rushforth
Colony of living Chaetoceros elmorei, with many setae extending from the frustules.
Image Credit: Karthick Bala
Scanning electron micrograph of a single valve of Chaetoceros, showing the interior of the valve and two setae extending from it.
Image Credit: Karthick Bala
Scanning electron micrograph of several broken setae, no longer attached to a valve.