Maxilliped-Setation Adaptations to Habitat and Sexual Dimorphism of Feeding Claws in Uca perplexa and U. vomeris

Abstract

Abstract Maxilliped-setation in two Australian fiddler crabs, Uca perplexa (n = 104) and U. vomeris (n = 128) was studied and related to the habitats in which these crabs live. Both species were collected from the banks of Myora Springs, North Stradbroke Island, Queensland, Australia. We counted the total number of setae (both plumose and spoon-tipped) on: 1) the inner and outer surfaces of the first and second maxillipeds, and 2) the inner surface of the third maxilliped. In general, there is no distinct sexual dimorphism for both types of setae in the two species. For any given size of crab, significantly more spoon-tipped setae were present in U. perplexa than in U. vomeris, providing further quantitative evidence that fiddler crabs from sandy habitats possess more spoon-tipped setae (an adaptation for processing sandy sediments) than those living in muddy habitats. No significant difference in plumose setation between the two species was generally detected; perhaps plumose setation is of less adap...