Abstract:
Relatively little is known about sound production and associated behaviours in crustaceans. Studies have concluded that certain species of crustaceans produce sound, however, with the exception of a few species, explanations of the mechanisms producing these sounds and their behaviours is still largely speculative. All species of Ovalipes are presumed capable of producing sounds based primarily on anatomical observations (ridges on the underside of the chela). The aim of the present study was to identify sounds produced, the mechanism producing these sounds and the associated behaviours in the paddle crab, Ovalipes catharus. Using controlled tank-based experiments containing both acoustic and video monitoring equipment, crab behaviour was analysed in relation to different social groups (individual, single sex, mixed sex and juveniles) and different naturally occurring scenarios (mating, feeding). Ovalipes catharus produced three distinct sounds: rasps, zips and bass. Rasps were produced by males, females and juveniles and increased significantly during mating and feeding events. Crabs producing a rasp sound showed no obvious external movements consistent with a mechanical sound production mechanism, such as stridulating. The source of this rasp sound may be from within the body of the crabs. The zip and bass were produced only by males and were associated with mating with male-male competition. The zip sound was produced using the previously described ridges. From the current study, the mechanism generating the bass was suggested to be internal and also coincided with a swaying motion of the body and digging movements of the first walking legs. In conclusion, O. catharus produce two sounds which don’t use the previously described ridged chelipeds. Indicating that sound production in crustaceans is not limited to hard external structures, implying that sound production may be more wide-spread among decapod crustaceans than previously assumed.
