Visually mediated species and neighbour recognition in fiddler crabs (Uca mjoebergiandUca capricornis)

Abstract

Mating signals are often directed at numerous senses and provide information about species identity, gender, receptiveness, individual identity and mate quality. Given the diversity of colourful body patterns in invertebrates, surprisingly few studies have examined the role of these visual signals in mate recognition. Here, we demonstrate the use of claw coloration as a species recognition signal in a fiddler crab (Uca mjoebergi). Furthermore, we show that distinct carapace colour patterns in Uca capricornis enable males to discriminate between their female neighbours and unfamiliar females. This is the first empirical evidence of the social importance of colour markings in fiddler crabs and the first example of visually mediated species and neighbour recognition in invertebrates other than insects.

The male blue crab,Callinectes sapidus, uses both chromatic and achromatic cues during mate choice

“…Fiddler crabs (Uca spp.) have been shown to use color cues in sex recognition, individual recognition and mate choice (Detto et al, 2006;Detto, 2007). In brachyuran crabs, the claws, in particular, are commonly used in sexual and agonistic communication (reviewed by Schöne, 1968;Christy, 1987).…”

“…Animals use color to communicate information such as sex (Butcher and Rohwer, 1989;Marquez and Verrell, 1991), reproductive readiness (McLennan and McPhail, 1990;Sköld et al, 2008), individual or species identity (Losos, 1985;Detto et al, 2006), social status (Rohwer, 1975;Watt, 1986) and individual quality (Endler, 1980;Hill and Montgomerie, 1994). However, colors can only be effective signals or cues if they can be perceived by the intended receiver (Rowland, 1979).…”

The fiddler crabUca mjoebergiuses colour vision in mate choice

“…The walking legs, carapaces and chelae of ocypodid crabs, particularly the well-studied fiddler crabs (genus Uca), are often brilliantly coloured (Crane 1975). However, despite this array of colours and their likely role in social displays (Detto et al 2004(Detto et al , 2006Hemmi et al 2006), there is still some debate over whether ocypodid crabs are actually capable of colour vision and what role it might play. At least, two spectrally distinct classes of photoreceptor are required for colour vision (Goldsmith 1990) but the number possessed by fiddler crabs is still in question.…”

“…Females leave their burrows and wander through the colony in search of a male before mating within his burrow. Males wave their enlarged yellow claw at any moving, crab-sized object, and females have been shown to use the coloration of the male's claw to recognize conspecifics (Detto et al 2006). Females have a strong preference for uniformly yellow claws over those painted red and white, and are even able to discriminate between natural yellow claws and those painted with a yellow that appears very similar to the human visual system (Detto et al 2006).…”

Visual recognition of conspecifics in the American lobster, Homarus americanus

“…Fiddler crabs (Uca spp.) can distinguish species and mates when natural patterns are modified with paints and typically approach unpainted unfamiliar rather than familiar conspecifics (Detto et al 2006). Vision can also be important for the resolution of fights (e.g.…”