CHORDATES AND FISHES

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Chapter 41

• CHORDATES AND FISHES

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Phylum Chordata

• Subphylum Vertebrata
• dorsal nerve surrounded by vertebrae
• cranium (skull)
• Endoskeleton (cartilage
• or bone)
• 45,000 species (24,000
• are fish)

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Phylum Chordata

• Subphylum Vertebrata cont
• Organs are organized into 10 systems skeletal,
  muscular, integumentary, digestive, respiratory,
  circulatory, excretory, immune, nervous, and
  reproductive

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7 Classes of Vertebrates

• Agnatha - (jawless fish) lampreys hagfish
• Chondricthyes - sharks, rays, and skates
• Osteichthyes - bony fish
• Amphibia - frogs, toads, salamanders
• Reptilia - reptiles
• Aves - birds
• Mammalia - mammals

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Evolution of Vertebrates

• Appeared 550 million yrs. ago
• 1st vertebrates were jawless fish w/ bony scales
  cartilage skeletons
• 1st fish w/ jaws evolved 400 million yrs. ago
• paired fins increased stability
• jaws evolved from 1st pr. of gill arches
  (skeletal supports of the pharynx)

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EVOLUTION OF JAWS
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ADAPTATIONS FOR LIFE IN H2O

• STREAMLINED SHAPE MUSCULAR TAIL
• PAIRED FINS ALLOW UP DOWN AND RIGHT LEFT
  MOVEMENT
• MUCOUS OVER SKIN REDUCES FRICTION
• GILLS FOR GAS EXCHANGE
• KIDNEYS FILTER WASTE
• GAS BLADDER

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ADAPTATIONS CONTD

• LATERAL LINE SYSTEM - ROW OF SENSORY ORGANS
  CONNECTED BY NERVES TO THE BRAIN - DETECTS
  VIBRATIONS IN WATER
• HIGHLY DEVELOPED SENSES OF SMELL, VISIONS, HEARING

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CLASS AGNATHA

• Ex HAGFISH LAMPREYS
• JAWLESS FISH
• EEL-LIKE BODIES
• Cartilaginous skeleton
• No plates or scales
• Keep notochord
• UNPAIRED FINS
• NO lateral line system

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CLASS AGNATHA

• HAGFISHES

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HAGFISH (only in ocean)

• LACK VERTEBRAE
• BITES OFF CHUNKS OF FLESH W/ 2 PLATES ROUGH
  TONGUE-LIKE ORGAN
• BURROW INTO DEAD FISH THROUGH GILLS, SKIN OR ANUS
  (eeee!!) EAT INTERNAL ORGANS
• TO EVADE PREDATORS THEY TIE THEMSELVES IN KNOTS
  SECRETE FOUL-TASTING SLIME

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CLASS AGNATHA

• LAMPREY

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LAMPREYS (most fresh water)

• HALF ARE FREE-LIVING DO NOT FEED AS ADULTS
• HALF ARE PARASITES AS ADULTS FEED ON BLOOD AND
  BODY FLUIDS
• ATTACHES TO HOST W/ DISK-SHAPED MOUTH, SCRAPES A
  HOLE W/ ROUGH TONGUE, SECRETES ANITCOAGULANT
• HOST BLEEDS TO DEATH, DIES FROM INFECTION, OR
  RECOVERS

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• LAMPREY
• MOUTH

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LAMPREYS CONTD

• SOME LAMPREYS SPEND ALL OR PARTS OF THEIR LIVES
  IN SALT WATER
• External fertilization
• LARVAL YOUNG RESEMBLE LANCELETS

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CLASS CHONDRICHTHYES

• SKELETON MADE OF CARTILAGE
• 800 SPECIES
• Ex SHARKS, RAYS, SKATES
• Moveable jaws, skeletons, and paired fins
• Carnivorous
• ALMOST ALL ARE MARINE
• PLACOID SCALES - SMALL TOOTH-LIKE SPINES THAT
  FEEL LIKE SANDPAPER (reduce turbulence)

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Class Chrondrichthyes
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ADAPTATIONS OF CARTILAGENOUS FISH

• GILLS FOR GAS EXCHANGE
• SPIRACLES - HOLES BEHIND EYES WHICH TAKE IN WATER
  WHEN SOME SPECIES LIE ON THE OCEAN FLOOR
• NH3 (AMMONIA) IS CONVERTED INTO LESS TOXIC GAS
  (urea)
• RECTAL GLAND REMOVES Na AND Cl - IONS IN BLOOD
• LIVER TAKES UP 25 OF TOTAL WEIGHT
• Lipids give them buoyancy

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ADAPTATIONS CONTD

• INTERNAL FERTILIZATION
• MALE USES CLASPERS TO TRANSFER SPERM TO FEMALE
• Some lay eggs
• SOME SPECIES RETAIN EGGS BEAR YOUNG ALIVE
• No prenatal or postnatal care

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SHARKS

• LARGEST - feed on plankton
• 1. Whale shark - 60 ft.
• 2. Basking shark - 50 ft.
• ADAPTATIONS
• 1. Swim w/ side-to-side motion because of
  asymmetrical tail
• 2. 6 to 20 rows of replaceable teeth (may replace
  20,000 teeth during lifetime!!!)
• 3. Pectoral fins - paired fins near head

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SHARK ADAPTATIONS CONTD

• 4. Olfactory bulbs
• parts of brain that connect w/ nerve cells from
  nostrils
• produce extreme sense of smell
• 5. Well-developed lateral line
• 6. Acute vision in low light
• 7. Pits of Lorenzini - holes in head that detect
  electrical fields
• 8. Largest brain of any fish

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Whale Shark
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Megamouth
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RAYS AND SKATES

• Flattened bodies
• rays bodies are diamond-shaped or round
• skates bodies are triangular
• bottom dwellers
• feed on mollusks crustaceans
• some have venomous spines in their tails

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SKATE
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Giant Manta Ray
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CLASS OSTEICHTHYES

• Three key characteristics
• Bone (skeletons)
• Lungs or swim bladder (early ones had lungs swim
  bladders are for buoyancy)
• Scales (protection and reduce H20 resistance)

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CLASS OSTEICHTHYES cont

• Lobe-finned fishes (7 species)
• Fleshy fins supported by bones
• Ex lungfishes and coelacanth
• Extinct lobe-finned fishes are ancestors of
  amphibians and other terrestrial vertebrates

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African lungfish
Coelacanth
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CLASS OSTEICHTHYES cont

• Ray-finned fishes
• Fins supported by rays (flexible pieces of bone)
• Fins lack a central bony axis
• Ex eels, perch, trout, salmon, guppies, bass

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CLASS OSTEICHTHYES cont

• External Anatomy
• Fins (supported by either spines or rays)
• Caudal (tail)
• 2 dorsal fins (anterior and posterior)
• Anal fin (ventral)
• Paired pectoral and pelvic fins
• Skin
• Scales (overlap like roof shingles)
• Point towards tail (reduce friction)

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Scales
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CLASS OSTEICHTHYES cont

• Internal Anatomy
• Major parts of skeleton
• Skull
• Spinal column
• Pectoral girdle (attachment point for pectoral
  fins)
• Like shoulder in humans
• Pelvic girdle (attachment point for pelvic fins)
• Like hips in humans
• Ribs

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CLASS OSTEICHTHYES cont

• Internal Anatomy cont
• Digestive System
• Mouth, pharynx, throat cavity, esophagus,
  stomach, intestine, anus
• Liver, gallbladder, and pancreas help with
  digestion in intestine

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CLASS OSTEICHTHYES cont

• Internal Anatomy cont
• Circulatory System
• Blood moves from heart arteries gills
  body
• tissues heart
• 4 chambered heart
• Deoxygenated blood empties into sinus venosus
  chamber
• Moves to atrium then ventricle then to conus
  arteriosus chamber

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CLASS OSTEICHTHYES cont

• Internal Anatomy cont
• Respiratory System
• Gills used for gas exchange
• Water flows into mouth, pumped over gills, exits
  out operculum
• Countercurrent flow (water and blood flow in
  opposite direction)
• Allows for more oxygen to pass over gills

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CLASS OSTEICHTHYES cont

• Internal Anatomy cont
• Excretory System
• Kidneys filter waste from blood (make urine)
• Urine moves from kidney to bladder and then
  expelled

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CLASS OSTEICHTHYES cont

• Internal Anatomy cont
• Swim Bladder
• Sac in abdomen (contains O, CO2, and N)
• Used to adjust density by regulating amount of
  gas in swim bladder
• Enables them to move up or down

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CLASS OSTEICHTHYES cont

• Internal Anatomy cont
• Nervous System
• Parts of the Brain
• Cranial nerves- connect sensory organs to brain
• Cerebrum (forebrain)- sensory info
• Optic tectum (midbrain)- processes info from
  visual, auditory, and lateral line system

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CLASS OSTEICHTHYES cont

• Parts of the Brain cont
• Cerebellum (hindbrain)- motor output
• Medulla oblongata (hindbrain)- controls body
  functions

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CLASS OSTEICHTHYES cont

• Spinal cord
• Carries nerve impulses to and from brain
• Spinal nerves connect spinal cord with internal
  organs, muscles, and sense organs

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Brain of a Fish
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CLASS OSTEICHTHYES cont

• Reproduction
• Separate sexes
• External fertilization
• Lay high s of eggs to ensure survival of some
  of them
• Some bony fishes bear live young
• Ex Mollies and guppies

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Spawning Fish