Marine FishesCh.7 Part 1: Jawless & Cartilaginous Fishes
Vertebrates • What defines a vertebrate? • Backbone or spine • Spinal cord
Jawless Fishes • Most primitive • Feed by suction • round, muscular mouth • Rows of teeth • Elongated, cylindrical body (like snake) • No paired fins or scales Lampreys
Hagfishes • aka: slime eels • No eyes • Feed on dead or dying fishes • Ca bore into prey and eat from the inside out • Pours slime out of mucus sacs • Can fill a 2 gallon bucket instantly! • Don’t believe me?
Hagfish • Deep sea environment (1000 ft) • Been around 300 million years • No eyes—virtually blind • Highly acute sense of smell and touch • Smooth body helps it move around inside dead animal • Eat prey from the inside out • Slime • used as defense mechanism • Protein explodes when in water
Hagfish and Whale • Over 5,000 feet deep! • Over ½ meter long • Breathe in gill openings on sides of body • Eats several times its own weight in rotting flesh
Lampreys • Primarily freshwater • Breed in rivers and lakes, move to sea as adults • Attach to fishes and suck blood
Lampreys as food? Haggis: The national dish of Scotland. It is a sheep’s heart, lungs and liver minced up with oatmeal and cooked in the lining of the stomach for three hours. Yum.
Cartilaginous Fishes • Sharks, rays, skates, and ratfishes • Skeleton of cartilage • Lighter, more flexy than bone • Paired lateral fins for swimming Tiger Shark
Cartilaginous Fishes • Movable jaws and teeth • Mouth is ventral • Underneath the head
Cartilaginous Fish • Placoid Scales • Rough, sandpaper like • Pointed tip that points backward • produces a covering that offers low resistance and turbidity • copied in the body suits of Olympic swimmers.
Sharks“The Heavyweight Champs of Evolution” • Read excerpt from The Devil’s Teeth (last paragraph, page 5). • Been around over 100 million years • The Frilled Shark – a living fossil • Let’s watch a movie: American Shark
The Perfect Predator: Body Shape • Torpedo shape • Body tapers at each end • Well developed, powerful caudal fin • Arching the body laterally into a shallow curve • Tremendous speed, low energy useage Mako Shark
The Perfect Predator: Coloration • Dark on dorsal (top) side • Light on ventral (bottom) side • Why? • White blends with light, dark blends with bottom The Great White Shark
The Perfect Predator: Teeth • Up to hundreds of teeth in jaw at one time • Embedded in flesh • Not attached to jaw • Multiple rows • Serrated • Replaced when lost – for entire life!
The Perfect Predator: Eyes • Extremely sensitive • Able to magnify amount of light • Rolls eyes backwards when attacking • Exposes tough, fibrous coat
The Perfect Predator: Nostrils • ONLY used for smell • Skin flaps • Inflowing/outflowing current • Water passes over lamellae • Lamellae • Covered with millions of sensory cells • Single drop of blood in an Olympic size pool • Smell is directional • Can tell where it’s coming from
The Perfect Predator: Ampullae of Lorenzini • Thousands of small capsules filled with jelly • Picks up vibrations in water of prey • Detects electrical fields of moving animals • Detects magnetic field of earth • Used in migration • More detail
Let’s watch some hunting • Planet Earth’s “Shallow Seas” video clip • Ch. 4, 36 minutes in • Ch. 6, 48:30, Diaries
Other Sharks: Whale Shark • Largest shark (and fish) in ocean • 65ft, 10+ tons • Filter feeders • Fish eggs • Plankton • Krill • Small fish and squid • Process over 6000 gallons of water/hr
Other Sharks: Hammerhead • Sensory mechanisms all along flattened scull • Head acts as airplane wing • Can detect a billionth of a volt • Excellent 3-D eyesight • Excellent navigation
Importance of sharks • Meat • Nutritional, boneless, mild-flavoring • Eyes • Corneas used as substitutions for human corneas • Skin • Used in research and engineering of ships, aircraft, pipelines and swimming suits
Importance of sharks • Liver • Contain high amounts of vitamin A (helps us see) • Squaline • Skin rejuvenator • Cartilage • Cancer research • Ecosystem • Apex predators • Control disease • Quick article
As Sharks Vanish, Chaotic New Order Emerges • What are some impacts that have resulted in the overfishing in sharks on the east coast of the US? • In your own words, what is an “apex predator?” • What is an example of a “trophic cascade?” • What is shark “finning?” What are some problems with it? “This is how we do it in Oklahoma, boy.”
Sharks are in great decline • Overfishing • K-selected species • Low fecundity • Do not produce many young • Reproduce every two years • Slow growth • Late age of maturation • Great White: 9 years; Sandbar: 25 years • Cartilage: • It cures cancer! NO IT DOESN’T! No evidence! • $100 million-a-year industry • Read page 23 in thesis, 2nd paragraph
Sharks are in great decline • Bycatch • Occurs in several fisheries: tuna longline, shrimp trawl, and swordfish • Millions of sharks a year • Finning • Removing the fins and discarding the carcass • This makes me sick to my stomach…
Shark Finning Play up until turtles
Why can’t we all just be friends?How to Hug a Shark Don’t try this at home
Characteristics • Adapted to living on bottom of ocean • Flattened bodies • Gill slits (5 pairs) on underside of body • Feed on clams, crabs, small fishes
Stingrays • Lie camouflaged in sand • Finds food by smell, touch and electrical senses • Up to 6 ft across • Spine found at base of tale laced with poison • Use in defense only
A closer look at the tail • This is a bull ray • Same type of ray that killed Steve Irwin
Manta Rays • Largest of all rays • Up to 22 feet across (average size is 12 ft)
Electric Ray • Organs on side of head that produce electricity • Shocks up to 200 volts • Used to stun prey • Used by Romans to cure treat headaches and other ailments • Confrontational if harassed. • Swim directly up to diver
Skates vs. Rays • Rays live bearing (viviporous) • Skates are egg bearing (oviporous) • Rays have longer, skinnier tale with spine • Skates have fleshier tale, no spine • Rays have plate like teeth • Skates have small teeth • Which is which?