Fish 101 for the Hobbyist: The Fish’s Body and Senses

Getting Acquainted with Aquarium Fish
If you are thinking of buying an aquarium or caring for freshwater or marine fish, then it doesn’t hurt to have a basic understanding of fish anatomy and how fish use their senses. That way, you’ll have more confidence when the time comes to selecting your aquarium fish.

The Body of the Fish
The fish’s body primarily features such organs or appendages as gills, a swim bladder, fins, and a lateral line.

The Gills: Gills enable the fish to take in oxygen from water. They are the fish’s lifeline with respect to respiration much like lungs in human beings.
The Swim Bladder: The swim bladder is the part of the fish that enables them maintain their water column which is also referred to as buoyancy. The air-filled organ is also referred to as an air bladder which is also called fish maw.
The Fins: The fins on a fish are used to direct the fish through the water and are parts of a fish's anatomy which enable them to propel or steer through water. Bottom fish or slower moving fish possess rounded fins. Faster moving fish generally display fins that are longer and more pointed.
The Lateral Line: The lateral line of the fish is a sensory organ that alerts it to movement. Therefore, this organ helps schools of fish move in schools with their movement comprised of synchronized movements that aid a fish in detecting predators.
The Scales: Scales on a fish are used to protect it as it moves through the water. The scales actually are translucent and therefore are devoid of color The source of the vibrant hues you see in tropical fish are pigment cells called chromatophores. They are located in the dermal layer of the skin.
The Skin: A thin layer of epidermal tissue covers the scales which also produce the fish’s slimy texture. The mucous coating allows the fish to swim through the water more easily, thereby lessening any friction.
The Mouth: The mouth on the fish is located at the end of its snout and determines whether or not the aquatic animal is a bottom feeder or feeds at the top. An upturned mouth indicates the fish is a surface feeder while a downward turned mouth represents a fish that feeds at the bottom of the tank. The size of the fish’s mouth also notes the size of food a fish will eat as well.
The Eyes: The eyes on a fish are similar to a human eye except a fish lacks eyelids.
The Ears: While fish do not, obviously, have an external ear, they do have an internal ear structure that is not outwardly noticeable.
The Nares: Instead of a nose, fish have nasal passages called nares. Water passes in and out of the nares, which are situated above the mouth and below the eyes. Any odors are communicated through the nares via a large nerve that travels up to the fish’s brain.
The Taste Buds: Taste buds on a fish are located in the mouth as well as external surfaces, such as the skin, fins, and lips.

Knowledge You Can Take with You to the Pet Store
The above basic overview can help you to get acquainted with your aquarium fish and assist you in the selection process, including care and feeding.

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