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Class Chondrichthyes: Class Chondrichthyes: cartilaginous fishes cartilaginous fishes The class Chondrichthyes has The class Chondrichthyes has two subclasses: two subclasses: Elasmobranchii, which includes the Elasmobranchii, which includes the sharks and rays. sharks and rays. Holocephali: the chimaeras: Holocephali: the chimaeras: ratfish and ghostfish. ratfish and ghostfish.

Class Chondrichthyes: cartilaginous fishes The class Chondrichthyes has two subclasses: Elasmobranchii, which includes the sharks and rays. Elasmobranchii,

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Class Chondrichthyes: Class Chondrichthyes: cartilaginous fishescartilaginous fishes

The class Chondrichthyes has two The class Chondrichthyes has two subclasses:subclasses: Elasmobranchii, which includes the sharks Elasmobranchii, which includes the sharks

and rays.and rays.

Holocephali: the chimaeras: ratfish and Holocephali: the chimaeras: ratfish and ghostfish. ghostfish.

16.1

Figure 24.01

16.2

Figure 24.02

Class ChondrichthyesClass Chondrichthyes Modern Chondricthyes include the sharks, rays and Modern Chondricthyes include the sharks, rays and

Chimeras.Chimeras.

The Chondrichthyes’ well-developed jaws, highly The Chondrichthyes’ well-developed jaws, highly developed sense organs, powerful swimming ability and developed sense organs, powerful swimming ability and streamlined shape have enabled them to thrive as streamlined shape have enabled them to thrive as marine predators for more than 350 million years, as marine predators for more than 350 million years, as other groups have come and gone. other groups have come and gone.

There are just under 1000 living species, all of which There are just under 1000 living species, all of which have cartilaginous skeletons, even though they are have cartilaginous skeletons, even though they are descended from ancestors that had bone.descended from ancestors that had bone.

Class ChondrichthyesClass Chondrichthyes

The Chondrichthyes are an ancient group The Chondrichthyes are an ancient group that although not as diverse as the bony that although not as diverse as the bony fishes have persisted largely unchanged fishes have persisted largely unchanged for hundreds of millions of years.for hundreds of millions of years.

The oldest unambiguous Chondrichthyans The oldest unambiguous Chondrichthyans are found in the Early Devonian (Devonian are found in the Early Devonian (Devonian -- 416-360 mya). although there are older -- 416-360 mya). although there are older fossils of scales.fossils of scales.

Fossil history of ChondrichtyesFossil history of Chondrichtyes

One of the best known extinct genera is One of the best known extinct genera is CladoselacheCladoselache a pelagic marine predator a pelagic marine predator from the Devonian.from the Devonian.

It was shark-like in appearance. About 2 It was shark-like in appearance. About 2 meters long with a large gape and three-meters long with a large gape and three-pronged teeth. As in modern sharks the pronged teeth. As in modern sharks the teeth were arranged on a ligamentous teeth were arranged on a ligamentous band in a whorl-shaped arrangement.band in a whorl-shaped arrangement.

Fossil history of ChondrichtyesFossil history of Chondrichtyes

CladoselacheCladoselache had two dorsal fins, each had two dorsal fins, each preceded by a large spine.preceded by a large spine.

It also possessed paired pelvic and pectoral fins It also possessed paired pelvic and pectoral fins as in modern sharks, but the fins were much as in modern sharks, but the fins were much more broad based than in later sharks.more broad based than in later sharks.

The tail was symmetrical externally, but The tail was symmetrical externally, but internally asymmetrical with the notochord internally asymmetrical with the notochord extending into the upper lobe of the tail.extending into the upper lobe of the tail.

Cladoselache picture

http://www.dinosoria.com/poissons/cladoselache_03.jpg

Cladoselache

Cladoselache lacked the rostrum (snout) of modern sharks

Extant radiation of ChondrichthyesExtant radiation of Chondrichthyes

By the Jurassic (200-146 mya) sharks of modern By the Jurassic (200-146 mya) sharks of modern appearance had evolved. Several genera from that era appearance had evolved. Several genera from that era are still extant.are still extant.

The most distinctive feature of modern sharks is the The most distinctive feature of modern sharks is the rostrum or snout that overhangs the mouth.rostrum or snout that overhangs the mouth.

Less prominent, but also of major importance was the Less prominent, but also of major importance was the evolution of solid calcified vertebrae.evolution of solid calcified vertebrae.

Finally, the teeth are covered with thicker more complex Finally, the teeth are covered with thicker more complex enamel than in earlier sharks.enamel than in earlier sharks.

MegalodonMegalodon

Megalodon (Megalodon (Carcharodon megalodonCarcharodon megalodon) is ) is another extinct shark species that is the another extinct shark species that is the largest predatory shark known.largest predatory shark known.

Megalodon occurred from 28-1.5 mya and Megalodon occurred from 28-1.5 mya and at approximately 16m long (and with a at approximately 16m long (and with a mass estimated at 47 metrics tonnes) it mass estimated at 47 metrics tonnes) it resembled a massive great white shark resembled a massive great white shark and was the top ocean predator of its era.and was the top ocean predator of its era.

“Megalodon (gray and red) with the whale shark (violet), great white shark (green), and a human (blue) for scale. Note: The maximum size attained by C. megalodon is indicated by the 20 m scale.” From Wikipedia.

http://upload.wikimedia.org/wikipedia/commons/thumb/0/07/Megalodon_scale1.png/220px-Megalodon_scale1.png

http://upload.wikimedia.org/wikipedia/commons/thumb/7/71/Megalodon_tooth_ruler.jpg/220px-Megalodon_tooth_ruler.jpg

http://upload.wikimedia.org/wikipedia/commons/thumb/7/7a/Megalodon_shark_jaws_museum_of_natural_history_068.jpg/300px-Megalodon_shark_jaws_museum_of_natural_history_068.jpg

http://upload.wikimedia.org/wikipedia/commons/thumb/1/1f/Carcharodon_megalodon.jpg/220px-Carcharodon_megalodon.jpg

MegalodonMegalodon

MegalodonMegalodon preyed on anything it wanted preyed on anything it wanted including pinnipeds, sea turtles, and including pinnipeds, sea turtles, and frequently whales. frequently whales.

Fossil whale skeletons contemporaneous Fossil whale skeletons contemporaneous with with MegalodonMegalodon show bite damage clearly show bite damage clearly inflicted by inflicted by MegalodonMegalodon..

MegalodonMegalodon

MegalodonMegalodon when attacking large prey is when attacking large prey is believed to have focused its attack on the believed to have focused its attack on the rib cage area crushing the delicate organs rib cage area crushing the delicate organs within. within.

It also is believed to have bitten off It also is believed to have bitten off appendages immobilizing the prey.appendages immobilizing the prey.

MegalodonMegalodon

Megalodon’sMegalodon’s bite force has been bite force has been estimated at up to 10 times that of a great estimated at up to 10 times that of a great white shark and up to five times that of a white shark and up to five times that of a TyrannosaurusTyrannosaurus rexrex..

The large serrated teeth were deep rooted The large serrated teeth were deep rooted and and MegalodonMegalodon likely behaved like a great likely behaved like a great white, which shakes its head after biting, white, which shakes its head after biting, thus sawing through its prey.thus sawing through its prey.

Extinction of Extinction of MegalodonMegalodon

The formation of the Isthmus of Panama three The formation of the Isthmus of Panama three mya resulted in large changes in ocean currents mya resulted in large changes in ocean currents and reduced worldwide ocean temperatures. and reduced worldwide ocean temperatures.

MegalodonMegalodon preferred warmer sea temperatures preferred warmer sea temperatures and the loss of warm water habitat coupled with and the loss of warm water habitat coupled with a substantial decline in the diversity of whales a substantial decline in the diversity of whales (also as a result of changing ocean (also as a result of changing ocean temperatures) is most likely the cause of the temperatures) is most likely the cause of the species extinction.species extinction.

http://dsc.discovery.com/sharks/shark-types/thresher-shark.jpg

Thresher Shark

Class Chondrichthyes

Class ChondrichthyesClass Chondrichthyes

About 1000 living species divided into two About 1000 living species divided into two distinct groupsdistinct groups

Neoselachii [also known as Neoselachii [also known as elasmobranchs] (sharks, skates and rays) elasmobranchs] (sharks, skates and rays) about 950 species.about 950 species.

Holocephalii (ratfishes). About 33 species.Holocephalii (ratfishes). About 33 species.

NeoselachiiNeoselachii

NeoselachiiNeoselachii Galeomorpha: about 279 species of sharks with an Galeomorpha: about 279 species of sharks with an

anal fin. 1m to perhaps 18m in length. Sand tigers, anal fin. 1m to perhaps 18m in length. Sand tigers, mackerel sharks, threshers, basking sharks, mackerel sharks, threshers, basking sharks, hornsharks, whale sharks, nurse sharks, mako, great hornsharks, whale sharks, nurse sharks, mako, great white.white.

““Squalomorpha”: Not a monphyletic group. About 124 Squalomorpha”: Not a monphyletic group. About 124 species of deep sea sharks, dogfish, angel sharks. species of deep sea sharks, dogfish, angel sharks. 15cm to 7m.15cm to 7m.

Batoidea: skates and rays. At least 534 species. Batoidea: skates and rays. At least 534 species. Electric rays, Manta rays, stingrays, skates. 1-6m Electric rays, Manta rays, stingrays, skates. 1-6m long and up to 6 m wide.long and up to 6 m wide.

Figure 24.07

Diversity of sharks

Figure 24.co

Hammerhead Shark

Great White Shark

Two skates

Hammerhead sharks

Whale shark

Figure 24.12

Skate (left) and ray (right)

Spotted Ratfishhttp://www.elasmodiver.com/BCMarinelife/images/Spotted-ratfish.jpg

SharksSharks

Sharks represent a little less than half of the Sharks represent a little less than half of the elasmobranchs and most are specialized elasmobranchs and most are specialized predators.predators.

The largest species is the whale shark, which is The largest species is the whale shark, which is a plankton feeder, as is the basking shark and a plankton feeder, as is the basking shark and the megamouth shark, but most of the others are the megamouth shark, but most of the others are predators of fish, marine mammals, crustaceans predators of fish, marine mammals, crustaceans and whatever else they can catch.and whatever else they can catch.

Basking Sharkhttp://oursurprisingworld.com/wp-content/uploads/2008/02/disgusting_fishes_7-basking-shark.jpg

http://animals.nationalgeographic.com/staticfiles/NGS/Shared/StaticFiles/animals/images/primary/whale-shark-with-fish.jpg

Whale shark

SharksSharks

The extant sharks include at least two The extant sharks include at least two lineages and molecular studies suggest lineages and molecular studies suggest there may be several others included there may be several others included within these two.within these two.

The squaloid sharks are smaller brained, The squaloid sharks are smaller brained, mostly live in cold, deep water and include mostly live in cold, deep water and include the various species of dogfish, the the various species of dogfish, the megamouth, and cookie-cutter sharks.megamouth, and cookie-cutter sharks.

Lesser spotted dogfish http://www.malcolmnobbs.com/favourite/medium/lesser_spotted_dogfish2.jpg

http://vivaldi.zool.gu.se/Fiskfysiologi_2001/Course_material/Introduction_fish_evolution/Images/Cookie_cutters.GIF

http://upload.wikimedia.org/wikipedia/commons/d/dd/Megamouth_shark_japan.jpg

Megamouth shark

Cookie cutter sharks

Spiny dogfish http://elasmodiver.com/Sharkive%20images/Spiny%20dogfish%20059.jpg

SharksSharks

The galeoid sharks are the dominant The galeoid sharks are the dominant carnivores of shallow, warm, species-rich carnivores of shallow, warm, species-rich parts of the ocean.parts of the ocean.

They include hammerheads, tiger sharks, They include hammerheads, tiger sharks, threshers, mackeral sharks, and the whale threshers, mackeral sharks, and the whale shark. shark.

SharksSharks

Sharks are very well streamlined, but are Sharks are very well streamlined, but are heavier than water (because they lack a heavier than water (because they lack a swim bladder) and sink if not swimming swim bladder) and sink if not swimming forward.forward.

Sharks increase their buoyancy by having Sharks increase their buoyancy by having a large oil-filled liver that reduces their a large oil-filled liver that reduces their density, but not enough to prevent them density, but not enough to prevent them from sinking.from sinking.

Fossil history of ChondrichtyesFossil history of Chondrichtyes

The elasmobranch heterocercal tail contains The elasmobranch heterocercal tail contains numerous radial skeletal elements which make it numerous radial skeletal elements which make it flexible and the vertebral column extends into the flexible and the vertebral column extends into the dorsal lobe.dorsal lobe.

Its shape can be controlled by intrinsic muscles.Its shape can be controlled by intrinsic muscles.

When undulated from side to side the tail because of When undulated from side to side the tail because of its shape generates both forward and upward thrust, its shape generates both forward and upward thrust, which counteracts a shark’s tendency to sink, while which counteracts a shark’s tendency to sink, while the large flat pectoral fins also provide lift to keep the the large flat pectoral fins also provide lift to keep the head up.head up.

16.6

Figure 24.08

SharksSharks

A typical shark is about 2m long, but they A typical shark is about 2m long, but they range in size from a few miniature forms range in size from a few miniature forms that are 25 cm long up to perhaps 18m in that are 25 cm long up to perhaps 18m in length.length.

Despite their range of sizes all modern Despite their range of sizes all modern sharks share a suite of characteristics.sharks share a suite of characteristics.

Characteristics of sharksCharacteristics of sharks The cartilaginous vertebral centra of sharks are The cartilaginous vertebral centra of sharks are

distinctive.distinctive.

Adjacent vertebrae have depressions in their Adjacent vertebrae have depressions in their faces into which fit spherical remnants of the faces into which fit spherical remnants of the notochord.notochord.

This arrangement of a rigid vertebral column of This arrangement of a rigid vertebral column of calcified cartilage swivelling on bearings of calcified cartilage swivelling on bearings of notochord allows the axial skeleton to swing notochord allows the axial skeleton to swing from side to side.from side to side.

Characteristics of sharksCharacteristics of sharks

In addition to the neural and hemal arches In addition to the neural and hemal arches in the vertebral column, which protect the in the vertebral column, which protect the spinal cord and blood vessels, all sharks spinal cord and blood vessels, all sharks possess additional intercalary plates that possess additional intercalary plates that provide extra protection to the nerve cord provide extra protection to the nerve cord and blood vessels. and blood vessels.

Dorsal intercalary plate

Shark skinShark skin

Unlike earlier sharks, living species have their Unlike earlier sharks, living species have their skin entirely covered in dermal placoid scales, skin entirely covered in dermal placoid scales, which are small tooth-like structures (with which are small tooth-like structures (with enamel, dentine and pulp just like real teeth). enamel, dentine and pulp just like real teeth).

These scales give sharkskin a tough, leathery These scales give sharkskin a tough, leathery and abrasive feel. The skin is also very and abrasive feel. The skin is also very streamlined.streamlined.

16.15

Figure 24.18

Shark skin repels barnacles

Barnacles are a major source of drag on boats and on many marine mammals e.g. whales. However, shark skin doesn’t allow barnacles to grip and grow.

http://www.youtube.com/watch?v=1hihcIPG7xo&feature=relmfu

Mako shark skinMako shark skin

The shortfin mako shark is capable of The shortfin mako shark is capable of swimming in brief bursts at speeds swimming in brief bursts at speeds approaching 50mph (kph).approaching 50mph (kph).

Recent research has shown that its skin is Recent research has shown that its skin is able to reduce drag by bristling, which able to reduce drag by bristling, which creates tiny depressions across the creates tiny depressions across the surface of the skin (like those on a golf surface of the skin (like those on a golf ball).ball).

Shortfin mako Sharkhttp://elasmodiver.com/images/Shortfin-Mako-022.jpg

Mako shark skinMako shark skin

The 200 micrometer long scales when held at 90 The 200 micrometer long scales when held at 90 degrees to the shark’s body cause tiny vortices degrees to the shark’s body cause tiny vortices to form in between the scales.to form in between the scales.

These vortices prevent a turbulent wake from These vortices prevent a turbulent wake from forming, which would exert a backwards pull.forming, which would exert a backwards pull.

(Lang et al. 2008. Bioinspiration and Biomimetrics; New Scientist 15 Nov (Lang et al. 2008. Bioinspiration and Biomimetrics; New Scientist 15 Nov 2008, p.16)2008, p.16)

Shark teethShark teeth The placoid scales are modified in the mouth to produce The placoid scales are modified in the mouth to produce

the rows of replaceable teeth characteristic of sharks.the rows of replaceable teeth characteristic of sharks.

Each tooth in a shark can be rapidly replaced as it Each tooth in a shark can be rapidly replaced as it becomes worn or damaged. Teeth are not embedded in becomes worn or damaged. Teeth are not embedded in the jaw but arranged on a spiral or whorl shaped the jaw but arranged on a spiral or whorl shaped cartilaginous band in which replacement teeth are cartilaginous band in which replacement teeth are always developing behind the functional tooth.always developing behind the functional tooth.

Teeth in young sharks may be replaced as often as once Teeth in young sharks may be replaced as often as once every 8 days.every 8 days.

16.6

Figure 24.08

http://www.sharkattackphotos.com/Shark_Miscellaneous.htm

Figure 24.09

Sand tiger shark (note multiple rows of teeth)

Variation in tooth structureVariation in tooth structure

The type of teeth a shark possesses is The type of teeth a shark possesses is dictated by the prey it eats.dictated by the prey it eats.

Sharks that feed on crustaceans, mollusks Sharks that feed on crustaceans, mollusks and similar hard shelled prey have dense and similar hard shelled prey have dense arrays of flattened teeth designed for arrays of flattened teeth designed for crushing.crushing.

Fish feeders have long pointed needle-like Fish feeders have long pointed needle-like teeth for gripping.teeth for gripping.

Porbeagle shark’s (a fish eater) teethhttp://www.elasmodiver.com/Sharkive%20images/PorbeagleSharkTeeth001.jpg

Variation in tooth structureVariation in tooth structure

Sharks that feed on large prey such as Sharks that feed on large prey such as mammals have pointed lower teeth and mammals have pointed lower teeth and triangular serrated upper teeth for cutting.triangular serrated upper teeth for cutting.

Plankton feeders such as basking sharks Plankton feeders such as basking sharks have small non functional teeth.have small non functional teeth.

Blue shark upper (top) and lower jaws (bottom)http://www.marinebiodiversity.ca/shark/english/teeth.htm

Shark JawsShark Jaws

A shark’s jaws can open in a variety of different A shark’s jaws can open in a variety of different positions depending on the prey.positions depending on the prey.

This is because the upper jaw is attached This is because the upper jaw is attached flexibly to the chondocranium in two locations flexibly to the chondocranium in two locations (front and back) both of which can move. This is (front and back) both of which can move. This is called a called a hyostylichyostylic jaw suspension. jaw suspension.

(Movement of parts of the head skeleton is (Movement of parts of the head skeleton is called called cranial kinesiscranial kinesis.).)

Shark JawsShark Jaws

When the upper jaw is protruded, the When the upper jaw is protruded, the hyomandibular cartilage which braces the hyomandibular cartilage which braces the rear of the upper jaw (the palatoquadrate) rear of the upper jaw (the palatoquadrate) swings to the side and anteriorly which swings to the side and anteriorly which increases the distance between the right increases the distance between the right and left jaw articulations and the volume of and left jaw articulations and the volume of the mouth. the mouth.

Shark JawsShark Jaws

The increase in volume is possible The increase in volume is possible because the upper jaw attachment to the because the upper jaw attachment to the chondocramnium at the front is by elastic chondocramnium at the front is by elastic ligaments and so the upper jaw can move.ligaments and so the upper jaw can move.

The increase in volume powerfully sucks The increase in volume powerfully sucks water and food into the mouth.water and food into the mouth.

Great White Sharkhttp://img.dailymail.co.uk/i/pix/2007/07_03/19sharkDM_468x591.jpg

Shark JawsShark Jaws

Protrusion of the upper jaw moves the Protrusion of the upper jaw moves the mouth away from the head and allows a mouth away from the head and allows a bigger bite to be taken than would be bigger bite to be taken than would be possible if the upper jaw was immobile.possible if the upper jaw was immobile.

BitingBiting

The teeth on the upper jaw The teeth on the upper jaw (palatoquadrate) have evolved to bite (palatoquadrate) have evolved to bite chunks from large prey items.chunks from large prey items.

They are bigger than the teeth on the They are bigger than the teeth on the mandible and often curved and serrated, mandible and often curved and serrated, which enables the shark to saw off a big which enables the shark to saw off a big chunk of flesh.chunk of flesh.

Tiger Shark Teeth

BitingBiting

When biting a large prey animal a shark When biting a large prey animal a shark seizes the animal and sinks its upper and seizes the animal and sinks its upper and lower teeth into it. lower teeth into it.

The shark then protrudes its upper jaw The shark then protrudes its upper jaw which pushes its teeth deeper into the which pushes its teeth deeper into the wound and violently shakes its head from wound and violently shakes its head from side to side.side to side.

BitingBiting

The head movements from side to side The head movements from side to side saw off a large chunk of flesh, which saw off a large chunk of flesh, which results in massive bleeding. results in massive bleeding.

Great Whites kill large prey, such as sea Great Whites kill large prey, such as sea lions, by taking a big bite and then waiting lions, by taking a big bite and then waiting for the victim to bleed to death.for the victim to bleed to death.

Shark Eating

http://www.youtube.com/watch?v=oIy_eYj20_0

Prey detectionPrey detection

Sharks use a series of methods to detect Sharks use a series of methods to detect prey related to distance.prey related to distance.

Chemoreception is used to detect prey Chemoreception is used to detect prey from a distance and sharks appear to be from a distance and sharks appear to be able to detect odors as dilute a 1 part in 10 able to detect odors as dilute a 1 part in 10 billion. billion.

Prey detectionPrey detection Vibrations can also be detected from a distance Vibrations can also be detected from a distance

using the lateral line system.using the lateral line system.

Once a shark gets relatively close, vision takes Once a shark gets relatively close, vision takes over.over.

Sharks have very good vision at low light Sharks have very good vision at low light intensities. There is a high density of rods in the intensities. There is a high density of rods in the retina and a tapetum lucidum just behind the retina and a tapetum lucidum just behind the retina, which reflects light back through the retina, which reflects light back through the retina.retina.

Prey detectionPrey detection

In low light conditions the tapetum lucidum In low light conditions the tapetum lucidum is beneficial, but in bright light is not.is beneficial, but in bright light is not.

In bright light melanin containing cells In bright light melanin containing cells expand to cover the tapetum lucidum.expand to cover the tapetum lucidum.

Prey detectionPrey detection

If a familiar prey item is located an attack may If a familiar prey item is located an attack may occur quickly.occur quickly.

If the prey is unfamiliar (e.g. a person) the shark If the prey is unfamiliar (e.g. a person) the shark may circle to gather more information. may circle to gather more information.

Such a shark may bump the potential prey with Such a shark may bump the potential prey with its rostrum presumably to gather extra sensory its rostrum presumably to gather extra sensory information.information.

Shark attacks on humansShark attacks on humans 1990’s 514 documented unprovoked shark 1990’s 514 documented unprovoked shark

attacks on humans. About 13% fatal.attacks on humans. About 13% fatal.

In a typical year there are 3-4 fatalities In a typical year there are 3-4 fatalities worldwide.worldwide.

In U.S. most shark attacks are in Florida.In U.S. most shark attacks are in Florida.

http://www.flmnh.ufl.edu/fish/sharks/statistics/http://www.flmnh.ufl.edu/fish/sharks/statistics/2003attacksummary.htm2003attacksummary.htm

Shark attacks on humansShark attacks on humans

Great White, Tiger and Bull sharks are the big three for Great White, Tiger and Bull sharks are the big three for shark attacks.shark attacks.

International shark attack file statistics (documented International shark attack file statistics (documented attacks from1580-2007)attacks from1580-2007) White 237 attacks 64 fatalitiesWhite 237 attacks 64 fatalities Tiger 88 attacks 28 fatalitiesTiger 88 attacks 28 fatalities Bull 77 attacks 23 fatalitiesBull 77 attacks 23 fatalities

This total of shark deaths in 400 years is approximately This total of shark deaths in 400 years is approximately equal to the number of people who die annually in Britain equal to the number of people who die annually in Britain from falling out of bed.from falling out of bed.

Bull sharkhttp://www.sharkdiving.us/images/bull/07.jpg

Foraging strategies of sharksForaging strategies of sharks

Various sharks employ different strategies Various sharks employ different strategies to obtain prey.to obtain prey.

Great White SharkGreat White Shark

Great White sharks specialize in feeding on Great White sharks specialize in feeding on colonial seals and sealions, but also take a wide colonial seals and sealions, but also take a wide variety of other prey including dolphins, other variety of other prey including dolphins, other sharks, turtles and other fish. sharks, turtles and other fish.

Around sea lion nursery areas sharks attack the Around sea lion nursery areas sharks attack the mammals as they come and go. They remain mammals as they come and go. They remain deep in the water until a victim passes within deep in the water until a victim passes within range above. They then rocket to the surface range above. They then rocket to the surface like a trout after a mayfly often exploding out of like a trout after a mayfly often exploding out of the water and flinging the prey in the air.the water and flinging the prey in the air.

Great Whitehttp://elasmodiver.com/images/Great-White-Shark-002.jpg

http://imagecache2.allposters.com/images/pic/NYG/78027~Great-White-Shark-Posters.jpg

Great White shark attack (BBC Planet Earth)

http://www.youtube.com/watch?v=n-t2ayKadD0&feature=related

Great White SharkGreat White Shark

Great Whites appear to be relatively Great Whites appear to be relatively intelligent and there are reports of them intelligent and there are reports of them cooperating to attack a seal. cooperating to attack a seal.

There are also reports that they are very There are also reports that they are very curious and they will often raise their head curious and they will often raise their head out of the water to look something over.out of the water to look something over.

Great White SharkGreat White Shark

A lot of attacks on humans by Great A lot of attacks on humans by Great Whites are likely cases of mistaken Whites are likely cases of mistaken identity as a surfer on a surfboard looks a identity as a surfer on a surfboard looks a lot like a sea lion.lot like a sea lion.

Frequently people bitten by a Great White Frequently people bitten by a Great White are released. Humans (and sea otters) are released. Humans (and sea otters) lack of blubber results in them often being lack of blubber results in them often being released after an initial bite.released after an initial bite.

Shortfin makoShortfin mako

The shortfin Mako shark specializes in The shortfin Mako shark specializes in attacking fast moving prey such as tuna, attacking fast moving prey such as tuna, bluefish, mackerel, bonito, swordfish, bluefish, mackerel, bonito, swordfish, sailfish as well as dolphins and porpoises.sailfish as well as dolphins and porpoises.

A study of mako stomach contents of A study of mako stomach contents of sharks taken off of the eastern U.S. found sharks taken off of the eastern U.S. found that bluefish made up about 77% of the that bluefish made up about 77% of the diet by volume.diet by volume.

Shortfin makoShortfin mako

Because it hunts such fast prey, makos have to Because it hunts such fast prey, makos have to be fast and athletic. Its speed has been be fast and athletic. Its speed has been recorded at 50km/h (31 mph), but in bursts it can recorded at 50km/h (31 mph), but in bursts it can accelerate to 74 km/h (46 mph).accelerate to 74 km/h (46 mph).

Makos often leap high out of the water in pursuit Makos often leap high out of the water in pursuit of prey and there have been several instances of prey and there have been several instances of hooked makos landing on the decks of fishing of hooked makos landing on the decks of fishing boats.boats.

Mako shark muscles

The musculature in a mako shark that drives its tail is located closer to the central axis of the body than in most other fish. This reduces the amount of energy used in side to side motion and enhances thrust. (Tuna have a similar muscle arrangement).

http://www.youtube.com/watch?v=dcO1UHVNkEI

Shortfin makohttp://elasmodiver.com/Sharkive%20images/Shortfin%20Mako%20Shark%20053.jpg

Thresher SharkThresher Shark

A Thresher shark is instantly identifiable A Thresher shark is instantly identifiable thanks to the enormously elongated upper thanks to the enormously elongated upper lobes of its tailfin.lobes of its tailfin.

The tail plays a central role in their hunting The tail plays a central role in their hunting strategy. Either working alone or in strategy. Either working alone or in groups threshers surround groups of groups threshers surround groups of pelagic fish and stun or disorient them pelagic fish and stun or disorient them using their tails.using their tails.

http://www.shark-pictures.com/viewpic/thresher-shark-134.html

Thresher shark video

http://www.youtube.com/watch?v=BQrrW9VRMFQ

5:40-8:20

Tiger sharkTiger shark

Tiger sharks are indiscriminate consumers Tiger sharks are indiscriminate consumers and will eat almost anything.and will eat almost anything.

Their powerful jaws allow them to crack Their powerful jaws allow them to crack turtles shells and clams.turtles shells and clams.

Stomach contents of captured sharks have Stomach contents of captured sharks have included seals, sea snakes, birds, fish, included seals, sea snakes, birds, fish, squid and even old tires.squid and even old tires.

Tiger sharkTiger shark

Tiger sharks trail only great whites in Tiger sharks trail only great whites in numbers of attacks on people, but numbers of attacks on people, but because they will eat almost anything they because they will eat almost anything they rarely leave after biting a human, as great rarely leave after biting a human, as great whites often do.whites often do.

Tiger sharkhttp://www.fearbeneath.com/wp-content/uploads/2008/09/tiger-shark-roger-horrocks.jpg

Tiger sharks clips

Tiger sharks and turtles http://www.youtube.com/watch?

v=Q_D51Ui_XMI Tiger shark aggression towards video

camera http://www.youtube.com/watch?

v=5oiWFbDEe6I

Cookiecutter sharkCookiecutter shark Cookiecutter are bizarrely specialized predators that bite Cookiecutter are bizarrely specialized predators that bite

disk-shaped pieces of tissue out of much larger animals.disk-shaped pieces of tissue out of much larger animals. Cookiecutter sharks attach to their prey with their lips Cookiecutter sharks attach to their prey with their lips

and then quickly spin using their proportionally enormous and then quickly spin using their proportionally enormous teeth to carve out a piece of flesh.teeth to carve out a piece of flesh.

Cookiecutter sharks feed on megamouth, basking and Cookiecutter sharks feed on megamouth, basking and whale sharks as well as fish such as tuna and marlin as whale sharks as well as fish such as tuna and marlin as well as dolphins and whales.well as dolphins and whales.

Cookiecutter sharkCookiecutter shark

Cookiecutters are bioluminescent and appear to Cookiecutters are bioluminescent and appear to use this ability to attract victims. use this ability to attract victims.

On the ventral surface cookiecutter’s glow along On the ventral surface cookiecutter’s glow along their whole length except for a dark patch of skin their whole length except for a dark patch of skin under the jaw. under the jaw.

The bioluminescent areas hide the shark against The bioluminescent areas hide the shark against the light of the surface water, but the dark patch the light of the surface water, but the dark patch stands out and acts as a lure for predatory fish, stands out and acts as a lure for predatory fish, which when they attack end up being bitten by which when they attack end up being bitten by the shark.the shark.

http://www.shark-pictures.com/viewpic/cookie-cutter-shark-teeth-structure-625.html

http://www.youtube.com/watch?v=syISlRJTaw4

Whale SharkWhale Shark Whale sharks are filter feeder that sieve Whale sharks are filter feeder that sieve

plankton, krill and other small prey from the plankton, krill and other small prey from the water.water.

The prey is trapped using 10-cm long gill rakers, The prey is trapped using 10-cm long gill rakers, which are bristle-like structures that sieve the which are bristle-like structures that sieve the water before it passes through the gill slits.water before it passes through the gill slits.

Whale sharks filter about 1500 gallons (6000 Whale sharks filter about 1500 gallons (6000 liters) of water each hour. Basking sharks and liters) of water each hour. Basking sharks and megamouth sharks also filter feed. megamouth sharks also filter feed.

http://elasmodiver.com/Sharkive%20images/Whale-shark-061.jpg

Whale shark feeding

http://www.youtube.com/watch?v=uQrBwN39LJI