User:LepidopteraMonarch/New Sandbox

External Anatomy

 * Body
 * The perch has a long and round body shape which allows for fast swimming in the water. The mouth is found at the anterior end of the fish with the anus or cloaca located at the posterior before the tail, which is the remaining end of the posterior formed from vertebrae and the spinal cord . Perch are vertebrates with a flexible rod shaped notochord running down the length of the animal directly above the gastrointestinal tract and a hollow tube of nerve tissue creating the spinal cord directly above the notochord. Perch have an exoskeleton which is the outer shell and an endoskeleton which is the structural support inside the body, Perch are bony fish so these skeletons are composed of bone. The outside of the body is comprised of scales which originate from the mesoderm, Perch fish specifically have ctenoid scales . Fish have a lateral line (located along the body of the fish horizontally) which is a sense organ used to detect movement via vibrations from water movement.
 * Head
 * The head consists of the skull (formed from loosely connected bones), eyes, mouth, operculum, gills, a pair of nostrils (which has no connection to the oral cavity) and the spiracle . Perch have strong jaws with a lower jaw (Mandible) that protrudes outward as they stay close to the ground and an upper jaw (Maxilla) that is fixed in place. They have small brushlike teeth across their jaws and on the roof of their mouth, they are missing canine teeth most commonly seen in walleye or sauger fish . Fish have a spherical shaped lens in their eyes with a retina that has both rod and cone cells . The gills are located under the operculum on both sides of the head and are used to extract oxygen molecules from water and expel carbon dioxide; the gills have gill rakers inside the mouth.
 * Fins
 * Perch fins (dorsal, pectoral, pelvic, anal, and caudal) are made of bony fin rays and have no direct connection to the spine except for the caudal fin. Perch fish have two dorsal fins, a spiny dorsal fin towards the anterior of the body and a soft dorsal fin towards the posterior of the body. A pair of Pectoral fins which are found on each side of the middle of the body closer to the anterior end. A pair of Pelvic fins which are found on each side of the body below the pectoral fins. An Anal fin which is located between the anus and the caudal fin. A Caudal fin (supported by soft rays) which is located at the posterior end. The caudal fin is forked (split in half) and rounded . Perch fish lack an adipose fin most commonly seen on trout and salmon between the dorsal and caudal fins.
 * Sex Determination
 * External anatomy can be used to determine the sex of a perch fish in multiple ways. Fish have two posterior openings located on their abdomen, the anal and urogenital. In males, the shape of the urogenital opening is round and larger than the anal opening. In females, the urogenital opening is often a V- or U-shape which is a similar size to the anal opening. Also, Males usually have a more brown-red colored urogenital opening compared to females.

Internal Anatomy
The esophagus is a flexible tube that goes from the mouth to the stomach. The stomach is connected to the intestine via the pyloric sphincter. The intestines of Perch consist of the small intestine and large intestine; the intestines have many pyloric caeca and a spiral value, the small intestine consists of a part called the duodenum. The spleen is located after the stomach and before the spiral value. The spleen is connected to the circulatory system, not part of the digestive tract. The liver is composed of three lobes: one small lobe (includes the gall bladder) and two large lobes. Perch have long and narrow kidneys that contain clusters of nephrons which empty into the mesonephric duct. They have a two chambered heart consisting of four compartments: the sinus venous, one atrium, one ventricle, and conus. Perch fish have a swim bladder that helps control buoyancy or floating within the water, the swim bladder is only found in bony fish. In Perch, the duct connecting the swim bladder to the pharynx is closed so air is unable to pass through from the mouth, these fish are called physoclists. Specifically in Perch, the gas bladder can vary from 12% to 25% of Oxygen and 1.4% to 2.9% of Carbon dioxide gas. Perch fish reproductive organs include either a pair of testes (sperm producing) or a pair of ovaries (egg producing).