Shark's sense of smell?

Question

I fail to understand how sharks can smell something hundreds of feet away. How does smell travel through water?

Answer 1

It's a very good question. And the answer is indeed that smell always means to detect molecules of a substance that react with your receptors in your olfactory organs. In fact, you do not smell the airborne particles of what ever it is you smell, but the particles now dissolved in the mucus that covers your receptors. in other words, like a shark, you are actually smelling something in a liquid, only that it is not water but - sorry for the language - snod.

Now, the receptors that "detect" whatever particle you smell, are chemical receptors. Very much like taste receptors, they bind the particle, which causes the infulx of sodium and calcium, while potassium is pumped out of the cell. This change in intracellular calcium triggers the release of neurotransmitters that then cause the signal to be transported to your brain. In sharks and other elasmobranchs (sharks, skates, and rays) these receptive cells are in the olfactory epithelium of the nose. The bulbi olfactorii, the two club-shaped extensions of the brain that are responsible for smelling, are right behind the nose epithelium making the distance from receptor to central nervous analysis very short (and thus more efficient). The bulbi are also extremely big in elasmobranchs, and especially in those that rely on them more than others (like, for example, most skates).

For a particle to be smelled by the shark it has to be dissolved in the ambient water and brought to the olfactory epithelium either by curent or the shark actively swiming through it. As you can see already, the shark has one big advantage over us: there is no need to have an airborne particle to resolve in mucus to then be detected. it can be detected immediately from the ambient environment, i.e., water. The nose flaps of an elasmobranch are shaped in such a way that water will efficiently flow through them as the animal swims. As soon as the particle reaches the receptor cell, the shark can smell it. Sharks have an extremely low threshold, simply because their sense of smell has evolved to such a degree of sensitivity. So, that's how they can even detect minute concentrations of a stimulant in the water (in case of some amino acids 10 to the power -14 to 10 to the power -13 mol/L; which is very, VERY sensitive). As I mentioned above, smell and taste is basically the same thing, and so sharks actually can even enhance their detection abilities of chemical stimulants through gustation (taste).

By now, you probably understand that smelling something from great distances away, sharks are dependent on (a) the rate at which the stimulant dissolves in the water, (b) the current, and (c) their own motion through the water column. Consequently, sharks rely on their lateral line organ for long distance detection of interesting stimulants. This organ lies in a canal under the skin, where hair-cells, mechanoreceptors, detect changes in water pressure (somewhat similar to sound). I am afraid, gopigirl, that the ampullae of Lorenzi are actually detecting elctric fields, such as induced by salt molecules in the water or by the heart muscles of prey. They have nothing to do with olfaction.

I hope this helps a little.

Answer 2

Small molecules of 'smell' dissolve in the water and drift with the current. A shark will only smell you from a long distance if it is down current from you. Their sense of smell is so sensitive that they can detect blood in the water in incredibly dilute amounts. They then swim into the current to find the source of the blood or other smell. Of course the smell gets stronger the closer they get to the source.

Answer 3

Smell travels through water exactly the same way as through air.
Smell is just actual particles of whatever substance your smelling.
So, Yes, it's real sh*t that's going up your nose.
If we could allow water to pass through our respiration tracts we could probably 'smell' stuff in the water.
Animals that live in water can do it very easily.
As water is thicker than air (which is incidentally also a liquid) particles are held suspended in it for longer, making it easier to smell things further away.

Answer 4

Their noses have millions of little pores that the smell fills in. The faintest trace can be picked up in all of these little smell sensors. Much more of them than humans.

Answer 5

ampullae of Lorenzini on their snout; the sense of smell is due to chemo-reception....molecules that contain the odors pass thru the water just like those in air and stimulate the receptor cells in these ampullae; I have also heard that the lateral line on their side of body might have some of these receptors too, but it is largely sensitive to vibrations

Answer 6

Found loads of information on another Yahoo Answer here http://uk.answers.yahoo.com/question/index?qid=20060805041158AAHo9Oh

Answer 7

they can...that's what makes you a human and them a shark

Answer 8

probably something to do with tasting

Answer 9

dont no

Answer 10

dont know but it dose .//////////////////////