Shark basics

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    14-Jan-2017

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SHARK BASICS

SHARK BASICS

Sharks are cartilaginous fishMeaning their skeleton is made mainly of cartilageBelong to the class Chondrichthyes (cartilaginous fish)Subclass Elasmobranchii (Elasmobranchs)

Sharks

Basic anatomySharks

5 major fins.DorsalPectoralPelvicAnalCaudal (Tail)Sharks

Dorsal fins stabilizingPectoral fins lift and steeringPelvic fins stabilizing (clasping in males)Anal fins stabilizingCaudal fins forward momentum (propulsion)Sharks

Most sharks have heterocercal tailsThe upper lobe is larger than the lower lobeAnd they use a carangiform swim motionSharks

Most male cartilaginous fish, including sharks, have a modified pair of pelvic fins called the claspersThe claspers, or intromittent organs, are used to deliver sperm from the male to the femaleSharks

Most sharks have 5 gills, though some have sevenUnlike bony fish, shark gills are not protected by any coveringThey allow for gas exchange in the waterAllow sharks to breatheSharks

When sharks are on the ocean floor they are able to breathe using spiraclesSpiracles are a pair of openings just behind the fish's eyes that allow it to draw oxygenated water in from above.The spiracles aid the fish in breathing even when it is lying on the ocean bottom or buried in the sandSharks

Sharks

Sharks have very thick skin covered in dermal denticles which gives it the feel of sandpaperThese dermal denticles reduce turbulence when sharks are in motionSharks

The skin of female sharks is usually 3-4 times thicker than that of male sharksMost forms of mating involve biting, so the thicker skin is necessary to protect the internal organsSharks

The skin usually demonstrates countershadingColoring with a dark dorsal side and a light ventral sideAids in camouflageSharks

Shark teeth are embedded in the gums, not directly attached to the jawShark teeth are constantly replaced and are produced in rows Most sharks have 3 rowsTeeth are replaced on at a time, not a whole row at a time

Sharks

Shark teeth come in many different formsThe shape directly reflects the common prey of that shark speciesSharks

Sharks have well-adapted eyesUnlike bony fish, sharks can dilate and constrict their pupilsThey also have Tapetum Lucidum, a lining in the back of the eye that helps detect light in dim or dark areasSharks

Sharks also use their ampullae of Lorenzini to detect predators and prey, and to aid in navigationThe ampullae of Lorenzini are small electroreceptors located on the underside of the rostrumSharks

Sharks are able to detect pressure changes in the water, like all fish, by using their lateral lineEach pore (neuromast) contains a neuroreceptor used to detect motion/pressure changes Sharks

Sharks have a strong sense of smell, enables by nostrilsTheir olfactory sensors are located in the short duct between the anterior and posterior nasal openingsSome species can detect as little as one part per million of blood in seawaterSharks

Sharks have the ability to determine the direction of a given scent based on the timing of scent detection in each nostrilSimilar to how mammals hearSharks

Sharks have a sharp sense of hearingA small opening on each side of the head leads directly to an inner earSharks

Final external structure is the cloacaThe cloaca is an opening near the posterior end of the sharkIt is the opening for the digestive (solid waste), excretory (liquid waste) and reproductive system (gametes)Sharks

Sharks have a 3 loved liver filled with an oil called squalene that helps them stay afloat

Sharks

Sharks

Sharks circulatory systems are powered by a two chambered heartsSharks

Sharks have a complete digestive tract; beginning at the mouth and ending at the cloacaMany sharks have the unique ability to completely regurgitate their food Sharks

Sharks

Inside the intestine is a specialized structure called a spiral valve, which helps with digestion by increasing surface areaSharks

The spleen of the shark is triangular in shape and located near the posterior endThe spleen is part of the circulatory systemIt is involved in the production, degradation, and storage of red blood cells and is integral to the sharks immune systemSharks

The shark has a small pancreas located on the under side of the spleenThe pancreas should consist of two lobesIt provides secretions needed for digestion

Sharks

The reproductive organs are located near the anterior end of the sharkThey occur in pairs; testes in males, ovaries in femalesConnective tubes allow the reproductive cells to travel from the organs to the cloacaSharks