Marine FishesCh.7

Part 1: Jawless & Cartilaginous Fishes

Objectives

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

Bonus Feature: Fear Factor

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

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 useageMako 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!

Tiger Shark and it’s Teeth

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

Let’s watch “Air Jaws,” a movie on my favorite shark: Great Whites

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

Shark Fin Soup

Sharks in Deep Trouble

Why can’t we all just be friends?How to Hug a Shark

Don’t try this at home

Rays

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)

A New Species of Manta Ray

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?