REPRODUCTION
*The picture above displays the male claspers
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Dogfish reproduce through aplacental viviparity, which means the eggs hatch but the pups develop inside the mother. Mating time is during the winter and females are usually pregnant 18-24 months. Only male sharks have a sex organ called claspers, which are used to transport sperm from male to female; a process otherwise known as copulation. During this process, the clasper is inserted in the female, creating a channel between one end of the clasper and a tube called the urogenital papillae of the male. Then siphon sacs, muscular male bladders, force the sperm from the cloaca to the claspers and into the female where it will fertilize with the egg.
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GAS EXCHANGE
The gill slits at the side of the head are the focal point of gas exchange. The oxygenated water flows over the gill filaments after passing through the mouth and pharynx; gas exchange occurs and the deoxygenated water leaves through the gill slits. The gills are made of feathery, threadlike filaments on either side of the pharynx. The oxygen rich water is pumped over gills and the water diffuses into deoxygenated blood vessels. These sharks are able to deliver oxygen more efficiently to their muscles because of their blood composition; where unlike other types of bony fish, they have fewer but larger red blood cells and their hemoglobin has twice the affinity for oxygen. Like many other chordates, they also maximize gas exchange through counter-current exchange.
LOCOMOTION
The shark moves by the post anal tail and by lateral undulation; alternating contracting muscles on either side of the back bone while creating an S-shaped wave that moves down the shark's body to help propulsion. The shark uses paired fins and rudders for stabilization and to get an extra speed boost. They have streamline bodies in order to decrease friction and they have body tissues denser than water to help minimize any possible friction. They use the natural oils in their liver to achieve maximum buoyancy, allowing them to float at any depth without sinking or using to much energy. Their tooth leg scales are rough and tough to the touch, featuring numerous grooves that help reduce the drag effect, providing the shark with a movement advantage.
FEEDING AND NUTRITION
The dogfish is fairly small for a shark but it is built to eat. It has flat blunt teeth that can bite down on the hardest of prey, such as crabs and lobsters. As a scavenger and opportunistic feeder it can also eat mollusks, small shrimp, worms and almost anything edible that may wind up in its mouth. Food is taken through the mouth and travels down the esophagus into the stomach, which partially breaks it down. Then it's further processed in finger-like pouches called pyloric ceca.The pouches absorb nutrients from food. The liver and pancreas secrete digestive enzymes to help breakdown food as it passes through the digestive track. The intestines are the final step of the system that breaks down and absorbs nutrients before the undigested leftovers are excreted through the anus.