The fragile file clam has a pair of hinged, thin, asymmetric white valves and a red mantle with a fringe of long tapering pink and grey banded tentacles at its edge.

Also around the margin of the mantle are a row of tiny eyespots that can detect light and shade, and may alert the animal to the approach of a predator.

[3] It does this by opening and closing its valves and expelling water in a stream from either side of the hinge, a form of jet propulsion.

Sometimes it sheds the longest tentacles and can still swim effectively without them, increasing the frequency of valve clapping to maintain speed.

[5] It was originally thought that the energy for swimming was supplied aerobically through respiration with little input from anaerobic glycolysis and arginine phosphate.