These fibers are enclosed in a gel-filled tubule which has a direct opening to the surface through a pore. Each ampulla is a bundle of sensory cells that are enervated by several nerve fibers. Recent research suggests that the ampullae may also allow the shark to detect changes in water temperature.
This enables the shark to locate prey that are buried in the sand, or orient to nearby movement. The ampullae detect weak magnetic fields produced by other fishes, at least over short ranges. They appear as dark spots in the photo of a porbeagle shark head below. These vesicles and pores are found around the head of the shark and are visible to the naked eye. The ampullae of Lorenzini are small vesicles and pores that form part of an extensive subcutaneous sensory network system. It closes when the shark passes close to a objects and also during biting or feeding.įigure 1 : Ampullae of Lorenzini on a Porbeagle shark. This structure is a denticle covered membrane that protects the eye. This effectively boosts the visual signal, especially in low light levels giving sharks high visual acuity.Īnother modification found in some sharks is the presence of a nictitating membrane. The crystals reflect light that has already passed through the retina and redirects it back to restimulate the retina as it passes out through the eye. Essentially the structure consists of a layer of parallel, plate-like cells filled with silver guanine crystals. The shark eye has a reflecting layer called a tapetum lucidum located behind the retina. Sharks posses the basic eye structure that is found in all vertebrates, but with some modification.
#Zebra shark diagram full#
The most common type of jaw found in modern sharks allows the full jaw to swing down and forward in order to swallow larger prey items. The jaw can be attached to the cranium in different ways and this is generally related to the method in which the animal feeds. The most variable aspect of a shark skull is the jaw. However, The fastest swimming sharks (such as makos and porbeagles) tend to have lunate shaped caudal fins (homocercal) consistant with the requirement for maximum thrust. The strong non-lunate caudal fin (heterocercal) in most benthic shark species allows for unhampered swimming close to the seabed (i.e. Lift to counter this force is provided by the pectoral fins and the shape of the body (like an airfoil) working together. The upper lobe of the caudal fin produces the most thrust, and at least some of that would tend to force the shark downwards. The caudal fin has both an upper and lower lobe that can be of different sizes and the shape varies across species.The primary use of the caudal fin (hetereocercal or homocercal) is to provide thrust. The peduncle may also be horizontally flattened into lateral keels. The caudal peduncle may have notches known as precaudal pits found just ahead of the caudal fin. The tail region itself consists of the caudal peduncle and the caudal fin. Anal fins may be absent, but if present they are located between the pelvic and caudal fins. In males they have a secondary function as they are modified into copulatory organs called claspers. Pelvic fins are found near the claoca and are also stabilizers. These fins are used for steering during swimming and help to provide the shark with lift. Pectoral fins originate behind the head and extend outwards.
#Zebra shark diagram skin#
When spines are present they are defensive, and may also have skin glands associated with them that produce an irritating substance. These two fins may, or may not have spines at their origin. There are one or two fins present along the dorsal midline called the first and second dorsal fin. Each of the fins are used in a different manner. The fins of sharks are used for stabilizing, steering, lift and propulsion.
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