Upload
sheila-twigg
View
215
Download
0
Tags:
Embed Size (px)
Citation preview
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.