Smell

February 4, 2025

Olfaction

Sharks possess a pair of nares, just under the edge of their snout. They are separate from the mouth and throat and do not aid in respiration, instead they are used purely for olfaction. Each nare is divided into two channels by a nasal flap, the water enters one channel (incurrent) gets passed over an area called the olfactory rosette allowing chemoreception to take place, receptors are then stimulated on the olfactory lamellae, chemosensory information is then sent via the olfactory nerve for processing in the olfactory bulb located in the olfactory sac, an anterior extension of the brain.

After passing through the olfactory sac the water is then channelled out through the excurrent channel of the nare. If the shark detects a smell which it wants to investigate (e.g.: odour from prey or pheromones from a potential mate), it will swim in the direction of the scent moving its head back and forth (exaggerating its natural swimming motion), this ‘S’ shaped swimming pattern will allow it to detect the direction of the smell by following the most concentrated signal.

Sharks are well known for their sense of smell with detection distances of up to 1000m, the largest olfactory bulb known so far constitutes 18% of total brain mass and belongs to the great white shark.