shark basics

SHARK BASICS

Sharks are cartilaginous fish◦ Meaning their skeleton is made mainly of

cartilage Belong to the class Chondrichthyes

(cartilaginous fish) Subclass Elasmobranchii (Elasmobranchs)

Sharks

Basic anatomy

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5 major fins. Dorsal Pectoral Pelvic Anal Caudal (Tail)

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Dorsal fins – stabilizing Pectoral fins – lift and steering Pelvic fins – stabilizing (clasping in males) Anal fins – stabilizing Caudal fins – forward momentum

(propulsion)

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Most sharks have heterocercal tails The upper lobe is larger than the lower lobe And they use a carangiform swim motion

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Most male cartilaginous fish, including sharks, have a modified pair of pelvic fins called the claspers

The claspers, or intromittent organs, are used to deliver sperm from the male to the female

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Most sharks have 5 gills, though some have seven

Unlike bony fish, shark gills are not protected by any covering

They allow for gas exchange in the water◦ Allow sharks to breathe

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When sharks are on the ocean floor they are able to breathe using spiracles

Spiracles 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 sand

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Sharks have very thick skin covered in dermal denticles which gives it the feel of sandpaper

These dermal denticles reduce turbulence when sharks are in motion

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The skin of female sharks is usually 3-4 times thicker than that of male sharks

Most forms of mating involve biting, so the thicker skin is necessary to protect the internal organs

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The skin usually demonstrates countershading◦ Coloring with a dark dorsal side and a light ventral

side◦ Aids in camouflage

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Shark teeth are embedded in the gums, not directly attached to the jaw

Shark teeth are constantly replaced and are produced in rows ◦ Most sharks have 3 rows◦ Teeth are replaced on at a time, not a whole row

at a time

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Shark teeth come in many different forms The shape directly reflects the common

prey of that shark species

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Sharks have well-adapted eyes

Unlike bony fish, sharks can dilate and constrict their pupils

They also have Tapetum Lucidum, a lining in the back of the eye that helps detect light in dim or dark areas

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Sharks also use their ampullae of Lorenzini to detect predators and prey, and to aid in navigation

The ampullae of Lorenzini are small electroreceptors located on the underside of the rostrum

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Sharks are able to detect pressure changes in the water, like all fish, by using their lateral line

Each pore (neuromast) contains a neuroreceptor used to detect motion/pressure changes

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Sharks have a strong sense of smell, enables by nostrils

Their olfactory sensors are located in the short duct between the anterior and posterior nasal openings

Some species can detect as little as one part per million of blood in seawater

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Sharks have the ability to determine the direction of a given scent based on the timing of scent detection in each nostril

Similar to how mammals hear

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Sharks have a sharp sense of hearing

A small opening on each side of the head leads directly to an inner ear

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Final external structure is the cloaca The cloaca is an opening near the posterior

end of the shark It is the opening for the digestive (solid

waste), excretory (liquid waste) and reproductive system (gametes)

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

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Sharks’ circulatory systems are powered by a two chambered hearts

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Sharks have a complete digestive tract; beginning at the mouth and ending at the cloaca

Many sharks have the unique ability to completely regurgitate their food

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

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The spleen of the shark is triangular in shape and located near the posterior end

The spleen is part of the circulatory system It is involved in the production, degradation,

and storage of red blood cells and is integral to the shark’s immune system

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The shark has a small pancreas located on the under side of the spleen

The pancreas should consist of two lobes It provides secretions needed for digestion

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The reproductive organs are located near the anterior end of the shark

They occur in pairs; testes in males, ovaries in females

Connective tubes allow the reproductive cells to travel from the organs to the cloaca

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