Use of electroreception during foraging by the Australian lungfish.

MICHAEL WATT, CHRISTOPHER S. EVANS & JEAN M. P. JOSS

A diverse range of animals, including elasmobranchs and nonteleost fish, use passive electroreception to locate hidden prey. Anatomical studies on the Australian lungfish, Neoceratodus forsteri (Krefft 1870), have confirmed the existence of ampullary organs analogous in form to the electroreceptors of other nonteleost fish. Afferents from these ampullae project to regions in the brain that are known to process electrosensory information in other species, suggesting that N. forsteri possesses an electric sense that may be used during prey location. To explore this hypothesis directly, we first characterized food-locating behaviour in N. forsteri and then conducted an experiment designed to quantify the effects of manipulating electrical and olfactory stimuli from live prey. A small crustacean was housed in a specially-constructed chamber hidden beneath the substrate, which prevented emission of chemical, mechanical and visual cues, but allowed transmission of electrical impulses produced by muscle movement. Control treatments included presentation of electrically-shielded prey, a dead crustacean, and an empty chamber. In some treatments, a competing olfactory signal was presented simultaneously at the other end of the testing tank to assess the relative salience of this sensory modality. Accurate and sustained feeding movements were elicited by the crustacean in the unshielded chamber, even with a competing olfactory signal. In contrast, the abolition of electrical cues in the three control treatments reliably reduced the accuracy and frequency of feeding movements in the vicinity of the target chamber. These results demonstrate that N. forsteri is capable of perceiving the weak electric fields emitted by living animals, and suggest that it uses this information when foraging to locate prey in the absence of visual cues.

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