TRICAS, T.C.; BOYLE, K.S.; DALE, J.; Univ. of Hawaii, Honolulu: Sound production and social pairing in laterophysic butterflyfishes

All 87 species of butterflyfishes in the genus Chaetodon (family Chaetodontidae) have a laterophysic connection, a unique anatomical linkage between the swim bladder, lateral line and inner ear. This morphological feature is hypothesized to impart sound pressure sensitivity to the lateral line and inner ear during acoustic communication, but no evidence of sound production during social interactions was known for these fish. Field experiments demonstrate that conspecific intruders elicit aggressive vocalizations by C. multicinctus, a socially monogamous and territorial species. Bioacoustics experiments confirm that both sexes exhibit aggressive tail slaps that produce brief, broadband clicks with a peak frequency of 10,066 Hz. Both sexes also show subtle motor movements of the head, pelvic fins and abdomen during social interactions that are associated with the production of low intensity acoustic pulses at lower peak frequencies from 22 – 280 Hz. In order to identify differences in pairing behavior among laterophysic vs. non-laterophysic chaetodontids, we quantified intra-pair separation distances for five species in the field. Pairs of longnose butterflyfish, Forcipiger longirostris, (a non-laterophysic chaetodontid) spend an average of 83% of the time together (separated <1 m), whereas pairs of laterophysic species (C. auriga, C. lunulatus, C. multicinctus, C. ornatissimus) are paired for a lower proportion of time (42 – 71%). Wild monogamous pairs in which the laterophysic region was surgically disrupted, show a change in social pairing behavior compared to sham controls. These results are consistent with predictions that vocalizations are produced by laterophysic species, occur in specific social contexts and influence social pairing behavior. Supported by NSF IBN0137883.