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Hearing: Piranhas have acute hearing. An organ called the labyrinth is located within the skull and contains the inner ear as well as an organ that controls balance. The swim bladder acts as a resonator and amplifier of sound waves traveling through the water. The Weberian apparatus then transmits these sound waves to the ear. As mentioned earlier in the discussion of piranha classification, the Weberian apparatus is a chain of the small bones connecting the inner ear with the swim bladder.

Sight: The eyes of fish have a flat cornea and a rigid lens. The eyes of piranhas are best adapted for seeing in daylight, but may also possess a reflective layer on the retina that can enhance their night vision. This structure is similar to that of many other nocturnal animals such as cats and deer. They also have excellent color vision and may be able to perceive a wider range of colors than humans.In common with all fish, there are no eyelids. Found on the side of the piranhas' head, their eyes have a very wide lateral expanse of vision but a limited anterior stereoscopic field. At rest, the eyes of piranhas are very nearsighted, buth the lens can be moved forward and back by special muscles, allowing them to focus on more distant objects.

Smell: The paired nostrils are found on the dorsal surface of a piranha's head just posterior to its mouth. Each nostril or nasal pit consists of 2 openings separated by an easily seen flap of skin. Water entering the nostrils flows past a highly sensitive and much folded olfactory membrane. Special smell receptors in this membrane are connected with the portion of the brain that perceives smell. Experiments have shown that piranhas have an amazingly acute sense of smell, which aids them in locatin food in the often murky waters of their native habitat.

Taste: Piranha tast buds are concentrated within the mouth and pharynx, with a lesser number distributed on the lips. Many fish also have taste buds on their fins and bodies. Fish are not thought to have a particularly well-developed sense of taste, but we have all seen them quickly spit out a potential food item that is not to their liking.

Lateral line: The lateral line is a sensory organ found only in fish. It can be observed as a thin line of small pores on the mid-sides of piranhas extending form the rear of the gill plate to the tail. Under the scales of the lateral line is a canal filled with a jellylike substance and many sensory cells called neuromasts. This organ not only detects vibrations traveling through the water, but the direction of water currents as well. It's sensitive enough to respond to the pressure waves produced by the swimming or struggling motions of other fish. It can also detect the reflected pressure waves produced when the fish approaches an object. The lateral line organ is definitely an important navigational aid, being of particular importance during darkness or in turbid water. It is also useful in helping piranhas locate their prey.


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hastatus said:
The same thing is covered in some Piranha Books, including this link.

Pointing it out to you to save all the typing.
Wow that was an outstanding read Frank. Thanks for posting that I missed it some how
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