Fish Guide And Aquarium

FAQs About Aquarium Fish

October 26th, 2007 Subscribe To Our Feed

FAQs About Aquarium Fish.

Do fish have tongues? Can they hear? Do they sleep?

Stop scratching your head. We‘ve probed the annals of ichthyology to find the answers.

First of all, what is ichthyology? No, it isn’t some fungal disease that fish contract. The term refers to the study of fish.
Anyone who is really interested in fish can glean a deeper understanding of these aquatic creatures through books and other
informative resources on ichthyology.

Do Fish Have Tongues?

Most fish do have “tongue”. Their tongues, formed from a fold in the floor of the mouth, do not resemble the muscular
tongues of humans, and usually cannot be produced.

Some species of bony fish have teeth on their tongues, which help in the grasping of prey. The name of one genus of
argentinid fish, Glossanodon, literally means “tongue teeth”.

Can Fish Hear?

Yes, they can; but hearing abilities vary among species.

The sensory chambers of their inner ears are lined with sensory hair cells and each contains an otolith (ear stone).
When sound vibrations pass through them, the difference in frequencies between the dense otoliths and sensitive hair cells
are pick up by the auditory nerves.

Hearing is also facilitated by the swim bladders in some freshwater fish species like carp. The swim bladders of these fish
have series of small bones that are connected to the inner ears. These transmit vibrations to the inner ears, thus enabling
the fish to “hear”.

Do Fish Sleep?

This is a complex question. Deciding if a fish asleep depends on many factors, one of which is the definition of sleep.

In humans, the transition to sleep involves specified changes in the pattern of brain wave in the area of the brain called
the neocortex. As fish do not have the same degree of neocortical development as mammals, they do not display the
brain – wave patterns associated with sleep. So, as far as brain – wave patterns go, fish do not sleep.

However, if sleep is defined as a combination of a lowered metabolic rate, reduced physical activity, slower response to
stimuli and the assumption of a resting posture, then many fish do sleep.

Some species of fish like the parrotfish secure a suitable spot on the seafloor and secrete mucus to form a protective
envelop in which they spend the night, while others like tunas never stop swimming.

Perhaps the simplest answer to this question is: Fish can’t sleep because they don’t have eyelids!