Welcome to AquaLand!
Please wait for the textures and sounds to download,
then click on the guide to start your tour.
Today you will learn about fishes.
Your guide will lead you to several fish tanks.
When your guide stops, carefully examine the fish in
the tank and read the accompanying literature appearing
in this frame.
When finished, click again on your guide to continue
your tour in AquaLand.
Pay attention to all the information!
At the end of the tour you will have to fill in
a test. If you pass the test with a perfect
result, you will receive a special prize!
And now read on for basic information about fishes.
In the Phylum Chordata, animals with a backbone, there are generally
three classes of fishes: Class Agnatha which includes the lampreys and hagfish;
Class Chondrichthyes, the cartilaginous fishes which includes the sharks,
rays, and skates; and Class Osteichthyes, the bony fishes. Identifying characteristics
of Class Agnatha include a circular mouth, no jaw, no paired fins, and only
one nostril. Members of the Class Chondrichthyes have a skeleton made of
cartilage, jaws, paired fins, paired nostrils, scales, and a two-chambered
heart. Bony fishes are recognized by their skeleton made of bone, jaws,
fins, most with scales, and a two-chambered heart.
The Class Osteichthyes includes all bony fishes. Like all fishes they are
cold blooded vertebrates that breathe through gills and use fins for swimming.
This class has the largest number of living species of all scientific classes
of vertebrates, more than 23,500 species, which accounts for 96% of all
fish species. Bony fishes are classified based on comparative anatomy, embryology,
genetics, molecular biology, and the fossil record.
Bony fishes inhabit almost every body of water. They are found in tropical,
temperate, and polar seas. Bony fishes exist in fresh water, seawater, and
brackish environments.
Most bony fishes have a fusiform (rounded and tapering at both ends) body
shape. This body shape reduces drag and requires a minimum amount of energy
to swim. Most fish species have pigmentation contained in cells called chromatophores
which allows the fishes to change color. This coloration may serve as camouflage.
Color changes may be rapid and temporary. Some bottom-dwelling fishes change
color almost instantly to match the substrate.
All fishes have fins. Various bony fish families show degrees of fin fusion
and reduction. Fins help stabilize or propel the fish in the water. Fins
generally present on bony fishes are dorsal fins, the caudal fin, the anal
fin, pectoral fins and pelvic fins. On the head are the eyes which vary
in size depending on the particular habitat. The gill openings are covered
by a flexible plate called an operculum that protects the gills. The nostrils
of most bony fishes have no internal connections with the oral cavity. Mouth
shape and size are good indication of a bony fish's feeding habits.
The body of most bony fish species are covered with and protected by a layer
of plates called scales. Some bony fishes may have scales only on portions
of their body, and some species have no scales. The scales lay head to tail
which helps reduce drag. The most common types of scales are ctenoid and cydoid. Bony
fishes secrete a layer of mucus that covers the entire body and protects
a fish from infection. Although there are no external ear openings, sounds
are transmitted through the soft tissue to the inner ear. Like the ear,
the lateral line (a midbody line running from head to tail) senses distance
and low frequency vibrations and water direction flow.