Use of camouflage materials as a food store by the spider crabNotomithrax ursus(Brachyura: Majidae)

Abstract

Abstract In laboratory tests, the camouflage crab Notomithrax ursus utilised its algal mask as a source of food. Mask ingestion mainly involved the removal of algae from the carapace, with removal from legs occurring less commonly, implying different rates of algal turnover. When there was no other available source of food, crabs ate an average of 4.1 % of the mask per day but when an alternative source of food (mussel flesh) was available, only 2.8% of the mask was consumed per day. A variety of red, green, and brown algae were consumed. The dual role of the mask means that there is an interaction between camouflage and food storage. Our results suggest that for N. ursus, camouflage is more important because consumption constitutes only a minor part of mask turnover. The evolution of spider crab masking is discussed in relation to the published literature.