Class Chondrichthyes

JAWS

• Teeth are modified scales

• Bottom jaw is like a fork for grabbing and holding prey

• Top jaw is like a knife with serrated edges to cut through prey

• Bite strength: 132 lbs. between jaws = 22 tons/in2 at tips of teeth!

BODY

• Fusiform body• Usually

countershaded

CAUDAL FINS

Homocercal: top and bottom lobes are equal in length (GWS).

Heterocercal: top lobe is longer than bottom lobe.

SCALES

• Placoid scales

• Dermal denticles (skin teeth)

EXTRAS• Spiracles:

respiratory structures present in certain chondrichthyes located just behind the eyes. Water intake valves.

• Spiral Valve: In stomach; increases surface area for absorption.

• Squaline Oil: In liver; increases buoyancy.

MORE EXTRAS• Opportunistic

feeder: Feeds when the opportunity arises.

• Obligate swimmer: Must swim in order to respire.

• Tonic immobility: Process by which shark becomes “paralyzed” by turning it over on it’s back (It appears to go to sleep). This is a temporary state!

SENSES (in the order that they detect prey) 1. Hearing: sound

travels faster in water, attracted to low frequency sounds emitted by old, injured and /or dying fish

2. Smell: Blood trail (chum) stimulates sense of smell

3. Lateral line: feel vibrations from wounded prey

SENSES4. Vision: can spot

prey from 30 yards -nictitating membrane protects eyes.

5. Electroreception: (from Ampullae of Lorenzini) Jelly-filled sacs that detect electrical fields given off by all living things, open wounds, etc.--Can detect up to one millionth of a volt

6. Taste: upon contact with prey

REPRODUCTION

Oviparous: Young hatch from egg laid outside the mother. Cat shark, Horn shark, Swell shark

Viviparous: live born sharks. Each fertilized egg develops inside a separate compartment in the mother’s oviduct. Pup is feed via a placenta. Lemon, Blue, Bull, Hammerhead

REPRODUCTIONOvoviviparous: embryo

develops in a large yolky egg kept inside the female’s oviduct. Embryos hatch while still inside the mother then develop more before being born.

--Sand Tiger, Thresher display intrauterine cannibalism: where first pup to hatch in each uterus will eat its siblings.

Claspers: Two fingerlike projections at the base of the pelvic fins in MALE sharks, (skates and rays).

4 Most Dangerous Sharks

Great White

Tiger

Oceanic Whitetip

Bull

SHARK ATTACKS

• Most shark attacks occur on sunny days in near shore waters 20C or warmer.

• Great White sharks prefer colder waters.

• Most common body parts attacked are the calves and knees.

• Typically sharks will show an Agonistic Display before they attack: back is arched, pectoral fins are pointed down, and shark swims erratically.

WILL YOU BE ATTACKED?

• You have a better chance of being killed by a pig, bee, snake, elephant, plane or car crash.

• You have a better chance of winning the lottery.

• You have a better chance of getting struck by lightning twice in the same spot.

THE HARD TRUTH• Fisherman kill

between 30-100 million sharks / year.

• Sharks kill between 10-15 humans/year.

• That means that for every single human killed, there are 10 million sharks killed!

RAYS

• Identified by the presence of a barbed stinger on their tail.

• Swimmers can do the “Stingray Shuffle” to avoid getting stung.

• If a person gets stung, immerse the body part in hot water to denature (break down) the protein-based toxin.

Ray MigrationGulf of Mexico

SKATES

• Skates have a pointed “nose”, spots and thorns or spikes on their bodies, but no stinger.

• Egg cases are called “Mermaid’s Purses” and are commonly found washed up on beaches.

CHIMAERAS

• Often called Ratfish or Rabbitfish.• Have a venomous spine at the front of the

first dorsal fin.• Males have a 5th clasper on their head.