Sensory system of fish
Accurate, up-to-date information about the surrounding environment is very important in order to make optimal decisions about possible threats, prey, as well as mates. For humans our five senses (sight, hearing, smell, taste, and touch) tell us this information. Fish use the same set of senses, but differently as they are, of course, wholly submerged in water. An aquatic environment alters stimuli: sound travels faster in water than air; water refracts and absorbs light; and odours travel more slowly in ocean currents than by wind. Fish have adapted their senses to these changes. As with terrestrial species, some fish have better developed some of these sense over others in accordance to where they live, and how they feed. Fish have a sense of smell, and many have a sense of smell better than humans. Their nostrils usually look like small dents in front of their eyes which are called nasal pits. Most fish have eye structures similar to those of terrestrial mammals, they have colour vision, and some are even able to see ultraviolet light. In very low or no light conditions fish do not rely on their sense of sight, but have better developed other senses to compensate, as with terrestrial species living or active in no or very low light conditions. Fish do not have eyelids, and eyes bulge slightly out and are able to move each eye independently to maintain a 180° field of view on each side. Fish have a good sense of hearing, as their inner ears are adapted to sense vibrations in the water. They have otoliths (bone in the ear of fish) which vibrate relative to the sensory hair cells in the ear which is interpreted as sound. Otoliths can be used to identify fish species as their shape and appearance are unique to the species, or group. Fish do in fact have taste buds, and a sense of taste. While there are taste buds in the mouth, fish can also have taste buds in their palate and throat, in their gills, over their body surface, as well as in their barbels (those fish that have them). Fish have been found to use their pectoral fins as fingertips and gain information about their surroundings through touch. They are also sensitive to touch on their body surface. Another sense that fish have, but we do not, is the lateral line, which will be the topic of another blog.
Written by: Minke Tolsma
For further reading:
- Hara, T.J. 1975. Olfaction in fish. Progress in Neurobiology 5: 271-335.
- Hara, T.J. & Zielinski, B.S. 2007. Sensory Systems Neuroscience. Elsevier: California.
- Hardy, A.R., Steinworth, B.M., & Hale, M.E. 2016. Touch sensation by pectoral fins of the catfish Pimelodus pictus. Proceedings of the Royal Society B 283: 20152652
- Popper, A.N., Rogers, P.H., Saidel, W.M., & Cox, M. 1988. Role of the fish ear in sound processing. In: Sensory biology of aquatic animals(pp. 687-710). Springer, New York.