( nd study co-author created two paralle...)New research shows sharks use their noses and bodies to locate smells

nd study co-author, created two parallel, turbulent odor plumes – one using squid scent and the other a plain seawater control. Minimally turbulent ‘oozing’ sources of squid odor and seawater control were physically separated from sources of major turbulence by placing a brick downstream from each oozing source to create two turbulent wakes with one or the other flavored with food odor. This produced four separate smell targets for the sharks to locate.

"In addition, we also tested the sharks under two light conditions – fluorescent and infrared – and in two sensory conditions – with their lateral lines intact or lesioned by streptomycin," explained Gardiner.

According to the researchers, streptomycin, an antibiotic, interferes with the normal function of motion sensitive "hair cells," the receptor cells of the lateral line. At high doses it has been known to cause hearing and equilibrium problems in humans, senses that are also based on hair cells.

Sharks with their lateral lines intact demonstrated a preference for the odor plume over the seawater plume and, more specifically, for the odor source with the higher turbulence (the brick on the odor side) over the source of the odor alone (the odor-oozing nozzle). Plume and target preference and search time were not significantly affected by light condition.

In the light, lesioning the lateral line increased search time, but did not affect success rate or plume preference. However, lesioned animals no longer discriminated between sources of turbulent and oozing odor. In the dark, search time of lesioned animals further increased, and the few animals that located any of the targets did not discriminate between odor and seawater plumes, let alone targets.

"These results demonstrate for the first time that sharks require both olfactory and lateral line input for efficient and precise tracking of odor-flavored wakes and that visual input can improve food-finding when
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Source:Boston University

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