A General Look External Anatomy There are about 25,000 different species of fishes. This is more...
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Transcript of A General Look External Anatomy There are about 25,000 different species of fishes. This is more...
A General Look
External Anatomy
There are about 25,000 different
species of fishes. This is more than any
other vertebrate group.
They come in all shapes and sizes.
The largest is the whale shark.
The abundance of fish life is a reflection of the abundance of plankton.
Fish show almost infinite variety when it comes to color. They have
special skin cells called chromatophores.
These chromatophores can expand or contract to change
the color of the fish.
There are also many patterns. Many open water fish like this
tuna show countershading.
They tend to be dark on top and light on the bottom.
Why do you think they have this pattern?
Some fishes have a coloration pattern that allows them to blend
in to their environment.
Some fish have very colorful warning coloration.
This is often used if they are poisonous, dangerous, or taste
bad.
Many mid-depth fish are often red while lots of the deep water fish are
black and may have luminescent organs.
Movement In Fishes
Propulsion in most fishes is
from the caudal fin and flexing the hind part of
the body.
The faster swimming fish
also have a teardrop or
fusiform body shape to help them move through the
water.
The dorsal and anal fins serve
primarily as rudders.
The pectoral and pelvic fins are
used for balancing ,
turning, braking and going
backwards.
Body Shapes
There are four basic body shapes with all kinds of variation in
between.
Compressed
Compressed fish look like they
have been smashed on both sides.
Depressed
Depressed fish look like they
were smashed from the top and bottom.
Terete or Round
These fishes are round like a
pipe. Most eels are in this
group.
Fusiform or Teardrop
This one we already
mentioned. Typical of the
faster fish species.
Scales
Actually, not all fish have scales. Lampreys and freshwater catfish
lack scales. The American eel actually has small scales.
There are four basic types that we’ll look at today.
Sharks and their relatives have placoid scales.
They feel a lot like sand paper.
Gar fish, reedfishes, and
parts of sturgeons have a scale type known as rhombic
or ganoid.
Ganoine gives them the “pearly”
look.
Most bony fishes have
one or both of the next two
types.
The bony –ridge scales: cycloid and ctenoid.
Cycloid are round and lack a “comb”
like edge.
Ctenoid have the comb like edge. Scales can be over 7 inches!
Circulation
The heart of a fish is simple when
compared to our heart.
They have a two cambered heart that follows a heart-gills-
body-heart path.
Oxygen is then taken out of the water by the gills
Internal Anatomy