The behavioural role of pit organs in the epaulette shark

Epaulette sharks Hemiscyllium ocellatum in three treatments, pit organs (free neuromasts) ablated, sham-operated and normal ( n  = 8 for each treatment), showed a significant preference for facing upstream in a flume ( P  < 0·05). There were no significant differences in the mean angles or angular variances among treatments. Individuals with ablated pit organs, however, spent significantly less time moving around than controls ( P  < 0·05), suggesting that pit organs contributed to motivation for activity. Pit organs do not appear to make an important contribution to rheotaxis in H. ocellatum . It is suggested that this may be due to structural differences in the pit organs of H. ocellatum compared with other species.