External Anatomy
Exterior surface of a perch is covered by a tough skin. This skin contains many mucous glands which produces the scales of the fish. The scales provide a protection for the surface of the body and are arranged in a pattern of longitudinal and diagonal rows. The posterior end of each scale covers the anterior end of the next scale. Each scale is produced in an epidermal pocket and grows posterior from the pocket. A scientist can determine the age of the fish by referring to the rings in its scale. The scale has numerous concentric ridges or annuli as well as many fine teeth on the posterior end of the scale, thus dubbed a ctenoid scale (see figure below).
Head
A head of a perch consists of a mouth, two eyes, and two nostrils. The head extends to the rear of the operculum. The operculum covers the four gills on each side of the head and is attached at the front end and also on the dorsal side. However, on the dorsal and ventral sides, there is an opening for the release of water.
Trunk
Trunk extends from the rear of the operculum to the anus. In this region, several fins are found attached. They include four unpaired median fins (two dorsal fins, one anal fin, and one caudal fin) and two sets of paired fins (two pectoral fins and two pelvic fins). These fins are membranous extensions of the skin which are supported by numerous fin rays. Fins are vital in swimming, stabilizing, and in directing movements through the water.
A lateral line is found on each side of a perch which extends from the operculum behind the eye to the tail. This line is essential because it acts as a specialized sense organ. This lateral line is able to detect vibrations and current directions in the water.
Tail
Tail extends from the anus on. The anus can be found anterior to the tail. Urogenital opening(s) is also located anterior to the tail. The female perch have a single urogenital opening (urinary pore and genital pore are one and the same) prior to the anus whereas the males have a separate genital pore and a urinary pore.
Internal Anatomy
Components of internal anatomy include:
Elements of Dermal Exoskeleton:
Chief supporting structure of the body consists of a bony endoskeleton. There are two types of bony endoskeleton:
Perch's muscular system is comparably simple than those of the terrestial vertebrates. Majority of the musculature in perch consists of myotomes (segmental muscles).
Contractions of these muscles lead to the flexing of the body which will aid a perch in swimming. Each myotome is separated by a myoseptum of a connective tissue as well as into dorsal and ventral parts by transverse septum. Separation of myotome into dorsal and ventral portions by a septum are known as epaxial muscles. The muscles that are on the ventral side of the transverse septum are called hypaxial muscles.
In the head, there are more specialized muscles which serve to move the jaws, opercula, mouth parts, lateral fins, and other parts associated with them.
On the posterior end of each gill, there are numerous fingerlike gill filaments (see figure below).
Each filament consists of many lamellae which have capillaries thus providing a large surface area for gas exchange. The large surface area permits gas exchange between these filaments and the capillary beds within each filament.
The fish gill is supported by a gill arch while gill rakers protect the gills and disallow coarse material from going through the gills.
The coelom of the perch consists of a peritoneal cavity and a pericardial cavity. The peritoneal cavity encompasses a stomach, a liver, other unmentioned digestive organs, swim bladder, and any unnamed visceral organs. The pericardial cavity surrounds the heart and is found anterior to the peritoneal cavity. See the below diagram.
Food enters the esophagus, the stomach, and then into the a small intestine. A large intestine leads from the small intestine before ending at the anus. Anterior to the small intestine are the three sacs is the pyloric caeca.
The heart is ventral to the gills and anterior to the pelvic fins. Perch's heart has a two-chambered heart. See figure below.
Blood passes from the sinus venosus to the atrium and from the atrium to the muscular ventricle. Contraction of the ventricle allows the blood to enter the conus arteriosus and exits through the ventral aorta. From the ventral aorta, the blood goes to the gills through the four pairs of branchial arteries.
The afferent branchial arteries enter the capillary beds in the lamallae found in the gills. Here, the blood is oxygenated which then goes to the efferent branchial arteries. The blood exits the efferent branchial arteries to be carried into the dorsal aorta. Arteries carry the oxygenated blood to the rest of the organs and tissue of the head, trunk, and caudal regions.
Perch has two divisions to its venous system. They are the hepatic portal system and the systemic veins.
In the hepatic portal system, veins carry the blood from the stomach, intestine, and other visceral organs. From these organs, the blood is then transported to the capillary beds in the liver. The hepatic vein collects the blood through posterior cardinals so the blood can be transported to the sinus venosus and to the heart for another round of circulation.
The systemic veins system consists of an anterior cardinal veins and posterior cardinals. The veins transport blood from the head while the posterior cardinals move blood from the posterior areas.
This system entails two kidneys which filter nitrogenous wastes from the blood. Once the wastes have been collected, the kidneys empty into the urinary bladder and then into the urogenital sinus. From the urogenital sinus, the wastes goes through the urinary pore. The diagram below shows both the male and the female urogenital system respectively.
There are two divisions of perch's nervous system:
Components of the perch brain are listed below in Table 1 and in Table 2, cranial nerves are displayed.
| Abducens | Lateral rectus muscle of eye |
| Acoustic | Inner ear and lateral line |
| Facial | Taste, lateral line, skin of head |
| Glossopharyngea | Gill muscles and lateral line |
| Oculomotor | Eye movements |
| Olfactory | Smell |
| Optic | Vision |
| Trigeminal | Jaw muscles, touch |
| Trochlear | Superior oblique muscle of eye |
| Vagus | Gills, heart, anterior part of digestive tract, lateral line |
Source: Lytle and Wodsedalek, 1991.
To return to the top of this page click here