Sound production and associated behaviours in the New Zealand paddle crab Ovalipes catharus

Despite growing evidence that crustaceans produce and detect sounds, the behavioural and biological function of these sounds is still poorly understood. Here, we describe sounds produced by the New Zealand paddle crab, Ovalipes catharus, and provide evidence of intraspecific communication using underwater sound. Acoustic and video analyses of tank-based experiments show that O. catharus produce at least three distinct sounds: the rasp, zip and bass. Notably, two of these sounds, the zip and bass, were directly correlated with post-copulatory mate-guarding and courtship behaviour and produced only by competing adult male crabs in the presence of a receptive female. Rasp sounds were produced by both sexes; the occurrence significantly increased in the presence of food, and play-back experiments of these sounds initiated a foraging-like behaviour. Responses to rasps might have evolved as a result of acoustic spying. Further, we show that both the rasp and bass sounds were produced by an alternative mechanism than stridulation of the chela ridges. This refutes widespread assumptions that Ovalipes crabs use only stridulation of ridges along their chelae to produce rasp-like sounds. Our results suggest that sound production in decapod crustaceans may be more widespread than previously presumed.