Smell and taste

 

 CHEMORECEPTION: OLFACTION AND GUSTATION

Chemoreceptionplays a major role in the lives of fishes. Nearly all aspects of life—feeding, prey detection, predator avoidance, species and sex recognition, sexual behavior, parental behavior, migration, etc.—are affected or mediated by the ability to detect water-born chemicalsand to react appropriately to these stimuli.

Chemoreceptioncan be conveniently divided into two basic types that, while essentially different, show some degree of overlap in their sensitivityto particular substances: olfaction (smell) and gustation (taste).

 

Olfaction(smell) results from stimulation of sensory receptor cellsin the olfactory organs, which are innervated by the olfactory nerve (cranial nerve I).

 

Lateral view of the brain and roots of the cranial nerves of a salmon: olfactory nerve (I), optic nerve (II), oculomotor nerve (III), trochlear nerve (IV), trigeminal nerve (V), abducens nerve (VI), facial nerve (VII), auditory nerve (VIII), glossopharyngeal nerve (IX), and vagus nerve (X)

 

Gustation (taste) is mediated by taste buds (sensory receptor cells)

and innervated by thefacial, glossopharyngeal, andvagusnerves (cranial nerves VII, IX, andX). Taste buds are found in the mouth cavity, as well as in the gill cavity, on the gill arches, and in some cases on external surfaces of the body (e.g., on barbels, fin rays, and/or skin).

 

Lateral view of the brain and roots of the cranial nerves of a salmon: olfactory nerve (I), optic nerve (II), oculomotor nerve (III), trochlear nerve (IV), trigeminal nerve (V), abducens nerve (VI), facial nerve (VII), auditory nerve (VIII),

glossopharyngeal nerve (IX), and vagus nerve (X)

 

A third type of chemoreception is often recognized, usually referred to as a commonor general chemical sense. It is mediated by sensory receptorslocated on exposed body surfaces of a fish, and better developed in scale-less, bottom-living forms.

 

Taste buds are not involved; instead, the receptors are free nerve endingssupplied by the spinal nerves. It is low in sensitivity compared to smelland taste.

 

 

 
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