Fish

History

• First vertebrates – 500 m.y.a.

• Fish are the most economically important marine organism– Fertilizer, feed,

protein

Classification• Kingdom- Animalia• Phylum- Chordata• Sub Phylum- Vertebrata (backbone)• Classes-

– Agnatha– Chondrichthyes– Osteichthyes

VertebratesFour fundamental

characteristics– Backbone

(vertebrae/spine)– Nerve cord (spinal cord)

•Protected by vertebrae– Skull– Bilateral symmetry

Classification• Kingdom- Animalia• Phylum- Chordata• Sub Phylum- Vertebrata (backbone)• Classes-

– Agnatha – jawless fishes– Chondrichthyes – cartilaginous fishes– Osteichthyes – bony fishes

AgnathaJawless fish: Lampreys,

Hagfish

AGNATHANS

Jawless fish - agnatha

Oldest group – very primitive

Scale-less skin

Some Parasitic / some filter feed

Circular mouth with fleshy teeth

Cartilaginous skeleton

Types of Agnathans• Hagfish - Scavengers, not much

known about them.• Lamprey- fresh and salt water;

parasitic and prey on other fish.* Both have cartilaginous skeletons

and sucker-like mouths.

ChondrichthyesCartilaginous Fish: Shark, Ray, Skate,

Chimaera

CHONDRICHTHYES

cartilaginous fish condrichthyes

Skeleton made of cartilage Sharks, rays, skates

All are predatory except 4 species!

The 4 exceptions are filter feeders

Whale sharks – warm shallow water

THE LARGEST FISH IN THE SEA!!!

The 4 exceptions are filter feeders

Basking sharks – cold shallow water

THE SECOND LARGEST FISH IN THE SEA!!!

The 4 exceptions are filter feeders

megamouth shark – cold deep water

The 4 exceptions are filter feeders

manta ray– shallow warm water

Chondrichthyes• Sharks adapted for a predatory

lifestyle.– Hydrodynamic body (fusiform)– Stiff pectoral fins (speed).

• Have live births.• Placoid scales.• Mantas, Sting Rays

– live in shallow water, have mouths located on the underside, fairly docile, wide flat bodies and wing-like fins that are flexible.

Types of Chondrichthyes• Sharks and Rays

– No operculum and must keep moving to breathe.

– Placoid scales that feel and look more like sandpaper.

– Skeletons made of cartilage not bone.

Types of Chondrichthyes• Chimaeras

– No operculum and must keep moving to breathe.– Scaleless– Bottom feeders– Longnose chimaera has a venomous spine

Chondrichthyes - SHARKS• Fusiform body shape• Caudal fin = heterocercal• 2 dorsal fins• Paired pectoral fins• ‘conveyor belt’ teeth• Cartilaginous skeleton

Chondrichthyes - SHARKSSPECIALIZED BODY PARTS• Extra oily liver for buoyancy• Lateral line• Ampullae of lorenzini• Keen olfactory & optical senses

They get a Bad Rap :-(

Watch “Planet in Peril: Battle Lines”

Species

Osteichthyes

Bony Fish: Salmon, Carp, Tuna

Over 20,000 different species

Types of OsteichthyesRay Finned:

– Most fish – Fins are supported by

bony structures called Rays.

– Teleosts are the most advanced (homeocercal tails and mobile fins).

Lobe Finned:– Fins are long, fleshy,

muscular, supported by central core of bones.

– possible ancestors of amphibians.

– Examples are: Coelacanth, Lungfish

Fish Characteristics

• Gills• Backbone• Paired Fins• Single Loop

Circulation• Two chambered

heart

Fish Anatomy

Fins

Different Dorsal Fins

Fish Respiration• Water flows over gills as fish

opens mouth and swims.• Water flows opposite

direction of blood flow.

• O2 diffuses from the water into the blood.

• Gills are made of thousands of gill filaments.

• Gills are covered by the Operculum.

Up Close and Personal

Fish Circulation• Fish heart has 2

chambers• Single loop

circulation• Blood flows into

gills, picks up O2, goes to the body, returns to the heart.

Fish Reproduction• Most Fish reproduce sexually, and

fertilize their eggs externally (Sharks-internally).

• Spawning is the process of fertilizing eggs.

• Baby fish are called FRY.

Fish Adaptations• Lateral Line System- used to detect vibrations, orient the

fish in water, it is a line of cells running down the side of the fish.

• Operculum- gill cover, movement of operculum allows more water to be drawn in.

• Swim Bladder- a gas filled sac that helps the fish maintain buoyancy. Sharks don’t have a swim bladder!

• Fins- Dorsal, Caudal, Pectoral, Pelvic, Anal.

Adaptations

Air Bladder Operculum Lateral Gills Line

Fins

Body forms of fishes1. fusiform

Sharks, tuna, bluefish

Streamlined, torpedo shaped

Fast long distance swimmers

Open water predators

Body forms of fishes2. compressed

Perch, butterfly fish, angelfish

Flattened laterally

Quick bursts of speed - short distance

Easily move in tight spaces

Body forms of fishes

3. depressed

Flounder, fluke, stingray

Dorso-ventrally flattened

Live on the bottom

Eyes on top of body

Color• Can be an important

identifying characteristic when dealing with live specimens. There may be no color in preserved specimens

• Color varies with habitat• Color varies between

males and females especially during breeding season

Body forms of fishes

4. attenuated

Eels, lamprey, pipefish

Elongated, tubular shape

Many Live in holes / burrows

Many secrete heavy mucus

Other Morphological CharacteristicsMouth Position

Taken from: Helfman et. al. 1997, The Diversity of Fishes

Other CharacteristicsMorphometrics and Meristics

Body parts of fishGet ready to draw a fish!!!

1. Caudal fin - tail fin

Used for forward motion and acceleration

2. Dorsal fin & 3. Anal fin

Singular finsUsed to prevent rolling/tipping

4. pectoral fin &

5. pelvic fin

paired fins (left & right)

Used to balance, stop & turn

6. Spines Used for protection

Some contain poison sacs

7. operculum Covers & protects gillsNot found in sharks

8. Lateral line Sensory canals used to detect changes in water pressure around the fish (similar to human ear)

Lateral Line and schooling

COMPARISON OF CARTILAGINOUS & BONY FISHES

TRAIT CARTILAGINOUS BONY_____

EXAMPLESSHARKS, RAYS, SKATES

TUNA, COD, SALMON,

SKELETON CARTILAGE BONE

SWIM BLADDER

ABSENT – OILY LIVER PROVIDES BUOYANCY

PRESENT – AIR FILLED FOR BUOYANCY

COMPARISON OF CARTILAGINOUS & BONY FISHES

TRAIT CARTILAGINOUS BONY_____

FERTILIZATION

INTERNAL – HAVE FEW LARGE YOUNG IN LIFE TIME

EXTERNAL – LAY MILLIONS OF SMALL EGGS

SCALES PLACOID – SPINY EMBEDDED IN SKIN

GANOID – PLATELIKE CTENOID & CYCLOID ARE FLAT, FLEXIBLE, OVERLAP

COMPARISON OF CARTILAGINOUS & BONY FISHES

TRAIT CARTILAGINOUS BONY_____ GILLS NO OPERCULUM

HAVE GILLS SLITS

HAVE OPERCULUM COVER & PROTECT GILLS

FEEDING BEHAVIOR

ALL PREDATORS FOUR EXCEPTIONS

GREAT VARIATION IN FOOD SOURCES

FINSRIGID AND UNSEGMENTED

Heterocercal tail

FLEXIBLE AND SEGMENTED

Homeocercal tail

TEETH NOT FUSED TO JAW -REPLACEABLE

FUSED TO JAW - IRREPLACEABLE