Filter feeding in the hermit crab : Pagurus bernhardus

The hermit crab, Pagurus bernhardus is able to remove both Artemia nauplii and unicellular algae from suspension. Crabs with wet weights of 1.1-9.2 g consumed all of the 300 Artemia nauplii contained in 200 ml of sea water within 1 h. Crabs weighing 0.7-1.1 g wet weight filtered suspended Dunaliella algae (8 μm) from concentrations of 10-350 million cells per liter at a rate of 26% and 47% within 2 and 5 h, respectively. A similar result was obtained with an 11 g crab. During filter feeding activity a water current is generated by the flagella of the exopods of the second and third maxillipeds. Artemia nauplii are caught by grasping movements of the endopods of the third maxillipeds, whereas filtering of unicellular algae is probably achieved by the two maxillae. It is assumed that filter feeding activity depends on the same structures and behavior as in deposit feeding. P. bernhardus is one more example of a benthic marine animal which may use any food source which becomes available in the course of the seasons.