KLIM
 |  موضوع: تشريح خارجي للسمك  4/4/2011, 05:16 | |
| Fish are animals that are
cold-blooded, have fins and a backbone. Most fish have scales and
breathe with gills. There are about 22,000 species of fish that began
evolving around 480 million years ago. The largemouth bass illustrated
above has the typical torpedo-like (fusiform) shape associated with many
fishes.
FINS are appendages used by the fish to maintain its position, move,
steer and stop. They are either single fins along the centerline of the
fish, such as the dorsal (back) fins, caudal (tail) fin and anal fin,
or paired fins, which include the pectoral (chest) and pelvic (hip)
fins. Fishes such as catfish have another fleshy lobe behind the dorsal
fin, called an adipose (fat) fin that is not illustrated here. The
dorsal and anal fins primarily help fish to not roll over onto their
sides. The caudal fin is the main fin for propulsion to move the fish
forward. The paired fins assist with steering, stopping and hovering.
SCALES in most bony fishes (most freshwater fishes other than gar that
have ganoid scales, and catfish which have no scales) are either ctenoid
or cycloid. Ctenoid scales have jagged edges and cycloid have smooth
rounded edges. Bass and most other fish with spines have ctenoid scales
composed of connective tissue covered with calcium. Most fishes also
have a very important mucus layer covering the body that helps prevent
infection. Anglers should be careful not to rub this "slime" off when
handling a fish that is to be released. (See Scales for more).
In many freshwater fishes the fins are supported by spines that are
rigid and may be quite sharp thus playing a defensive role. Catfish
have notably hard sharp fins that anglers should be wary of. The SOFT
DORSAL and CAUDAL FINS are composed of rays, as are portions of other
fins. Rays are less rigid and frequently branched.
THE GILLS are the breathing apparatus of fish and are highly
vascularized giving them their bright red cover. An operculum (gill
cover) that is a flexible bony plate protects the sensitive gills.
Water is "inhaled" through the mouth, passes over the gills and
"exhaled" from beneath the operculum.
Fish see through their EYES and can detect color. The eyes are rounder
in fish than mammals because of the refractive index of water and focus
is achieved by moving the lens in and out, not distorting it as in
mammals.
PAIRED NOSTRALS , or NARES, in fish are used to detect odors in water
and can be quite sensitive. Eels and catfish have particularly well
developed senses of smell.
The MOUTHS shape is a good clue to what fish eat. The larger it is the
bigger the prey it can consume. Fish have a sense of taste and may
sample items to taste them before swallowing if they are not obvious
prey items. Most freshwater fishes in Florida are omnivorous (eating
both plant and animal matter). Some are primarily piscivorous (eating
mostly other fish). The imported grass carp is one of the few large
fishes that are primarily herbivorous (eating plants). Fish may or may
not have teeth depending on the species. Fish like chain pickerel and
gar have obvious canine-shaped teeth. Other fish have less obvious
teeth, such as the cardiform teeth in catfish which feel like a
roughened area at the front of the mouth, or vomerine teeth that are
tiny patches of teeth, for example, in the roof of a striped bass'
mouth. Grass carp and other minnows have pharyngeal teeth modified from
their gill arches for grinding that are located in the throat.
The LATERAL LINE is a sensory organ consisting of fluid filled sacs with
hair-like sensory apparatus that are open to the water through a series
of pores (creating a line along the side of the fish). The lateral
line primarily senses water currents and pressure, and movement in the
water.
The VENT is the external opening to digestive urinary and reproductive
tracts. In most fish it is immediately in front of the anal fin.
As different as a man may be from a fish, both creatures share some
fascinating similarities in basic structure and function. And the closer
one looks, the more complex life becomes. The smallest units of life
are microscopic cells, and some organisms—such as an ameba—are no larger
than a single cell. In larger multicellular creatures, individual cells
that are similar in structure and perform a specific function are
grouped into tissues, and tissues may be grouped into even more complex
and specialized structures called organs. These organs perform the basic
bodily functions such as respiration, digestion, and sensory reception.
Man and fish share such organs as the brain, stomach, liver, and
kidneys. Other organs appear in different forms in different organisms;
for example, the lungs in humans and the gills in fish are very
different but both provide the same basic function of respiration.
Finally, some organs (such as the fish’s swim bladder) are simply not
present in man. Below are descriptions of some of the organs identified
on the opposite diagram, along with their functions. A number of other
vital organs, such as the spleen and pancreas, may also be present but
are smaller and more difficult to locate. A largemouth bass destined for
the frying pan makes an excellent specimen because this species is
large enough for easy examination. For anglers brave enough to do some
investigating while filleting their next fish, a fascinating experience
awaits!
SPINE: The primary structural framework upon which the fish’s body is
built; connects to the skull at the front of the fish and to the tail at
the rear. The spine is made up of numerous vertebrae, which are hollow
and house and protect the delicate spinal cord.
SPINAL CORD: Connects the brain to the rest of the body and relays
sensory information from the body to the brain, as well as instructions
from the brain to the rest of the body.
BRAIN: The control center of the fish, where both automatic functions
(such as respiration) and higher behaviors ("Should I eat that critter
with the spinning blades?") occur. All sensory information is processed
here.
LATERAL LINE: One of the fish’s primary sense organs; detects underwater
vibrations and is capable of determining the direction of their source.
SWIM (or AIR) BLADDER: A hollow, gas-filled balance organ that allows a
fish to conserve energy by maintaining neutral buoyancy (suspending) in
water. Fish caught from very deep water sometimes need to have air
released from their swim bladder before they can be released and return
to deep water, due to the difference in atmospheric pressure at the
water’s surface. (Most freshwater anglers in Florida need not concern
themselves with this!) Species of fish that do not possess a swim
bladder sink to the bottom if they stop swimming.
GILLS: Allow a fish to breathe underwater. These are very delicate
structures and should not be touched if the fish is to be released!
KIDNEY: Filters liquid waste materials from the blood; these wastes are
then passed out of the body. The kidney is also extremely important in
regulating water and salt concentrations within the fish’s body,
allowing certain fish species to exist in freshwater or saltwater, and
in some cases (such as snook or tarpon) both.
STOMACH AND INTESTINES: Break down (digest) food and absorb nutrients.
Fish such as bass that are piscivorous (eat other fish) have fairly
short intestines because such food is easy to chemically break down and
digest. Fish such as tilapia that are herbivorous (eat plants) require
longer intestines because plant matter is usually tough and fibrous and
more difficult to break down into usable components. A great deal about
fish feeding habits can be determined by examining stomach contents.
PYLORIC CAECA: This organ with fingerlike projections is located near
the junction of the stomach and the intestines. Its function is not
entirely understood, but it is known to secrete enzymes that aid in
digestion, may function to absorb digested food, or do both.
VENT: The site of waste elimination from the fish’s body.
LIVER: This important organ has a number of functions. It assists in
digestion by secreting enzymes that break down fats, and also serves as a
storage area for fats and carbohydrates. The liver also is important in
the destruction of old blood cells and in maintaining proper blood
chemistry, as well as playing a role in nitrogen (waste) excretion.
HEART: Circulates blood throughout the body. Oxygen and digested
nutrients are delivered to the cells of various organs through the
blood, and the blood transports waste products from the cells to the
kidneys and liver for elimination.
GONADS (REPRODUCTIVE ORGANS): In adult female bass, the bright orange
mass of eggs is unmistakable during the spawning season, but is still
usually identifiable at other times of the year. The male organs, which
produce milt for fertilizing the eggs, are much smaller and white but
found in the same general location. The EGGS (or ROE) of certain fish
are considered a delicacy, as in the case of caviar from sturgeon.
MUSCLES: Provide movement and locomotion. This is the part of the fish
that is usually eaten, and composes the fillet of the fishwith my pleasure
| |
|
خالد الرواضيه
| | موضوع: رد: تشريح خارجي للسمك 4/4/2011, 11:18 | |
| اشكر لك اختيارك الامثل تقبلوا خالص تحياتي | |
|
KLIM
| | موضوع: رد: تشريح خارجي للسمك 23/4/2011, 04:11 | |
| | |
|
ازهار القدس
| | موضوع: رد: تشريح خارجي للسمك 23/4/2011, 04:23 | |
| | |
|
KLIM
| | موضوع: رد: تشريح خارجي للسمك 23/4/2011, 04:26 | |
| | |
|
theredrose
| | موضوع: رد: تشريح خارجي للسمك 23/4/2011, 04:30 | |
| | |
|
KLIM
| | موضوع: رد: تشريح خارجي للسمك 23/4/2011, 04:34 | |
| | |
|
