Fish Anatomy
EXTERNAL FEATURES |
LOCATION |
PURPOSE/USE |
Caudal Fin |
Single tail fin |
Main propelling fin for most fish |
Dorsal Fin |
Single fin on top of the back |
Vertical stability in swimming |
Adipose Fin |
Single lobe shaped fin behind the dorsal fin on lower back |
Aids in stability |
Pectoral Fin |
Paired fins on either side of the body near the head |
Locomotion and side to side movement |
Pelvic Fin |
Paired belly fins |
Steering, braking, and balancing |
Anal Fin |
Single fin near the anus |
Lends stability in swimming |
Eye |
Paired on either side of head |
Sight organs |
Olfactory Pit |
Paired openings on front of snout |
Smell organs |
Gill Cover |
Paired openings on either side of head behind cheeks |
Protect gills |
Lateral Line |
Horizontal line on both sides |
Series of sensory pores that sense vibrations in the water |
Maxilla |
Paired flaps on sides of mouth |
Form a round enclosure to reduce the risk of prey escaping |
Fins
The fins of most fish consist of stiff rays covered by skin. Most fins are jointed and
separate near the edge of the fin. However, certain fish have rays that are bony, stiff
and unjointed called spines. Some species have both types of fins. For example, Bass have
a spiny dorsal near the front and a soft dorsal near the rear that are connected. The
number of rays in the fin is used in classification of the species.
Skin
The skin of fish consists of two layers. The Epidermis (outer) and the Dermis. The Epidermis
consists of cells arranged one above the other. Just like humans, these cells are constantly
shed and replaced. Interspaced between the skin cells are slime cells which produce mucoid
secretions that form the very important protective covering known as "slime".
Scales
The dermis of the skin consists of connective tissue, collagen, and blood vessels. The scales
lie in pockets in the dermis and extend out from the connective tissue. Scales are covered
by the epithelial layer mentioned above. Scales overlap to form a protective flexible armor
capable of withstanding trauma.
Gills
Respiration is carried out by means of gills located under gill covers on either side of the
head. There are several slit-like openings. Gills are attached to the connective tissue called
gill arches. Gills consist of a delicate system of blood vessels covered by a very thin
epithelium through which the gaseous exchange takes place.
Lateral Line
The lateral line consists of a series of scales, each modified by a pore, which connects to
a system of canals containing sensory cells and nerve fibers. It runs in a horizontal line
from the gill covers to the tail fin. The lateral line has been shown to be a very important
sensory organ in fish. It can detect minute electrical currents, vibrations (in and through
the water), and it serves as a kind of echo location process that helps the fish identify its
surroundings.
Coloration
Cells in the dermis produce the many exotic colors and patterns seen in fish. These cells are
named for the pigment they contain. Some fish can change color rapidly due to movement of
melanin grains within each cell. When dispersed, they absorb more light and the area of the
fish darkens. When tightened the fish looks pale.
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