FISH

CLASSIFICATION
• KINGDOM ANIMALIA
• PHYLUM CHORDATA
• SUBPHYLUM VERTEBRATA (BACK BONE
PRESENT)
• SUPRACLASS AGNATHA (JAWLESS FISH)
• CLASS MYXINI (HAGFISH)
• CLASS CPHALOSPIDOMORPHI (LAMPREY)
• SUPRACLASS GNATHOSTOMATA (JAWED FISH)
• CLASS CHONDRICHTHYES (CARTILAGINOUS
FISH)
• CLASS OSTEICHTHYES (BONY FISH)

PHYLUM CHORDATA
FIVE CHARACTERISTICS OF CHORDATES
• 1. HOLLOW NERVE CORD- IN VERTEBRATES IT
DIFFERENTIATES INTO BRAIN AND SPINAL CORD
• 2. NOTOCHORD- FLEXIBLE ROD PRESENT AT ONE STAGE IN ALL
CHORDATES; IN VERTEBRATES IT DIFFERENTIATES INTO
VERTEBRAL COLUMN THAT FORMS AROUND THE NERVE CORD
• 3. PHARYNGEAL SLITS - POUCHES THAT CONNECT PHARYNX
WITH OUTSIDE (BETWEEN MOUTH AND ESOPHAGUS). GILLS IN
SHARKS, FISH; PRESENT IN TERRESTRIAL ANIMAL EMBRYOS
BUT DISAPPEAR LATER EXCEPT EUSTACHIAN TUBE
(CONNECTING THROAT AND MIDDLE EAR)
• 4. POSTANAL TAIL- EXTENDS BEYOND ANUS; PRESENT AT
LEAST IN EMBRYO; REGRESSES INTO TAIL BONE IN HUMANS
• 5. SEGMENTATION- REFLECTED IN ARRANGEMENT OF
MUSCLES & IN VERTEBRAL COLUMN
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SUPRACLASS AGNATHA
(JAWLESS FISH)
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Class Cephalspidomorphi (Lamprey)
• Parasite
• attaches to other fish & sucks their blood
• lives in ocean
Class Myxini (Hagfish)
• Scavenger
• lives in the ocean
• known for its slimy secretions
Both have cartilaginous skeletons
and sucker-like mouths

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SUPRACLASS GNATHOSTOMATA
(JAWED FISHES)

CLASS CHONDRICHTHYES
(SHARKS & RAYS)
• HAVE SKELETONS MADE OF CARTILAGE NOT BONES (HAVE
BONE JAW).
• MOST SALTWATER/ VERY FEW FRESHWATER
• HAVE NO OPERCULUM (GILL COVER)
• SOME MUST KEEP MOVING TO BREATHE & OTHERS CAN PUMP
WATER OVER THEIR GILLS
• SPIRACLE- A MODIFIED SLIT BEHIND THE EYE, ASSISTS THE
SHARK WITH TAKING IN WATER DURING RESPIRATION AND
PLAYS A MAJOR ROLE IN BOTTOM DWELLING SHARKS.
• HAVE DIFFERENT KINDS OF SCALES THAT FEEL AND LOOK
MORE LIKE SANDPAPER.
• MULTIPLE ROWS OF REPLACEMENT TEETH THAT STEADILY
MOVE FORWARD LIKE A CONVEYOR BELT. SHARKS CAN LOSE
UP TO 30,000 OR TEETH IN THEIR LIFETIME.
• MOST SHARKS ARE COLD BLOODED
• CONTROL BUOYANCY WITH LARGE LIVERS THAT EXCRETE OIL
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CLASS CHONDRICHTHYES
(SHARKS & RAYS)
REPRODUCTION
• VIPAROUS- LIVE BIRTH
• VIVIPAROUS- EGGS HATCH INTERNALLY
• OVOVIVIPAROUS- LAY EGG CASES EXTERNALLY
(CALLED MERMAID’S PURSE)
• SEPARATE SEXES
• MALES HAVE CLASPERS
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CLASS CHONDRICHTHYES
(SHARKS & RAYS)
SENSORY
• AMPULLAE OF LORENZINI- ELECTRORECEPTOR
ORGANS USED TO DETECT THE
ELECTROMAGNETIC FIELDS ALL LIVING THINGS
PRODUCE. THEY NUMBER IN THE HUNDREDS TO
THOUSANDS.
• LATERAL LINE SYSTEM- DETECTS MOTION OR
VIBRATIONS IN WATER
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GENERAL ANATOMY OF A SHARK
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GENERAL ANATOMY OF A RAY
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Basking Shark is a filter feeder

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CLASS OSTEICHTHYES
(BONY FISH)
• BACKBONE MADE OF BONE
• FRESHWATER & SALTWATER
• GILLS WITH OPERCULUM (FEW HAVE LUNGS)
• FINS - DORSAL, CAUDAL, PECTORAL, PELVIC,
ANAL.
• SWIM BLADDER- A GAS FILLED SAC THAT HELPS
THE FISH MAINTAIN BUOYANCY. SHARKS DON’T
HAVE A SWIM BLADDER
• LATERAL LINE SYSTEM

TYPES OF OSTEICHTHYES
RAY FINNED:
– MOST FISH ARE THIS TYPE
– FINS ARE SUPPORTED BY BONY
STRUCTURES CALLED RAYS.
LOBE FINNED:
– FINS ARE LONG, FLESHY,
MUSCULAR, SUPPORTED BY
CENTRAL CORE OF BONES.
– THOUGHT TO BE ANCESTORS OF
AMPHIBIANS.
– EXAMPLES ARE: COELACANTH,
LUNGFISH

FINS

ADAPTATIONS
SWIM R BLADDER OPERCULUM
LATERAL LINE SYSTEM
Swim
Bladder

FISH ANATOMY

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.

CIRCULATION
• FISH HEART HAS 2 CHAMBERS
• SINGLE LOOP CIRCULATION
• BLOOD FLOWS INTO GILLS, PICKS UP O2, GOES TO THE
BODY, RETURNS TO THE HEART.

REPRODUCTION
• MOST FISH REPRODUCE SEXUALLY, AND
FERTILIZE THEIR EGGS EXTERNALLY
• SPAWNING IS THE PROCESS OF
FERTILIZING EGGS.
• BABY FISH ARE CALLED FRY.

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Coelacanth: living fossil, lobe-finned

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Cichlids

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Clown Fish (Nemo)

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Kissing Fish

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37The puffer fish uses air to expand its body
to look intimidating to predators

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