Chapter 18 Fish

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Chapter 18- Fish

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Vertebrate Chordates

• Phylum Chordata- internal skeleton of cartilage
  or bone vertebrae surrounding the dorsal nerve
  cord (develops from notochord).
• Fish
• Aquatic
• Gills
• Finscovered in scales
• Pectoral fins- located on anterior portion
• Pelvic fins located on posterior portion
• Dorsal fin located on dorsal area
• Caudal fin- tail fin
• Post anal fin sticks out past the cloaca
• Two-chambered heart
• All vertebrates developed from fish
• Fins developed into jointed appendages
• Ectothermic

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Gills

• Pharyngeal pouch Small pocket at the back of
  throat that becomes the gills
• Rows of gill filaments (fingerlike projections
  through which gases enter and leave the blood)
• Gill slit- Opening at rear of the cheek
• Operculum- Covers gills and draws water into
  fishs mouth
• Countercurrent flow- Water passes over gills in
  one direction as blood flows in opposite
  direction through capillaries
• 85 extraction of dissolved oxygen from water

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Blood Circulation

• Heart pumps blood to the gills
• Sinus venosus- Collects oxygen-poor blood from
  body
• Atrium- Delivers to ventricle
• Ventricle- Pumps blood to gills
• Conus arteriosus- Smooths flow of blood
• Oxygen-rich blood leaves gills to go to the rest
  of the organs

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Fish Heart Structure
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Kidneys and Reproduction

• Kidneys- Organs made of 1,000s of nephrons
• Nephron- Tube-like unit regulates the bodys salt
  and water balance and removes waste from blood
• Excess water and waste-urine

• Reproduction
• Most separate sexes
• External fertilization (spawning)
• Yolk sacks supply nutrients-stay attached to
  hatchlings
• Large numbers of eggs released to ensure some
  survive
• Sharks, skates, and rays have internal
  fertilization
• Claspers- Male organs used to insert sperm into
  female

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Subphylum Hyperotreti

• Class Myxini
• Hagfish
• Partial cranium (skull) no vertebrae
• Cartilage skeleton
• Lack jaws
• 4 pairs of tentacles around mouth

http//www.youtube.com/watch?vletqkpG3b5Q
http//video.google.com/videosearch?qhagfishslim
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agfish
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Subphylum Vertebrata

• 43,700 species
• Skeleton (cartilage or bone) grows as the animal
  grows
• Complete digestive system and a large coelom
• Closed circulatory system
• Respiration by gills, lungs, and in some cases,
  moist skin

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Class Cephalasidomorphi- Lampreys

• Agnatha ("no jaws") or the Cyclostomata ("round
  mouth").
• Long, eel-like, jawless fish
• No paired fins
• Free-swimming predators
• Hatch in freshwater Some migrate to the sea,
  return to freshwater to reproduce

http//video.google.com/videosearch?qlampreyatta
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lampreyqlamprey20emb0
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Range of Lamprey in n. America
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Fish Trivia
http//www.squidoo.com/fishtriviaquestionsandanswe
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Ostracoderms

• First were Placoderms- extinct
• Heavy armor plated
• Strong jaws-modified gill arches
• Paired pectoral and pelvic fins allow for better
  escape and predation

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Gnathostomata

• Jaws evolved from anterior pair of pharyngeal
  arches
• The skeletal supports for the pharyngeal slits
• More efficient gill ventilation and capture and
  ingestion of food
• Paired appendages

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Class Osteichthyes- Bony fish

• 20,000 species
• Marine and freshwater
• Lateral line system- Sensory system extending on
  each side
• Sensory cells with cilia detect vibrations to
  allow a fish to perceive its position in the
  water
• Optic tectum Area in a fishs brain that
  receives and processes info from visual, auditory
  and lateral line systems
• Two groups the lobe-finned (Sarcopterygii) and
  ray-finned fish (Actinopterygii)

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Sarcopterygii Lobe-finned fish

• 6 species of lungfish
• Found in stagnant or freshwater ponds
• Africa, South America, and Australia.
• 1 species of coelacanth
• deep oceans
• crossopterygian fish
• Muscular fins with large, jointed bones attaching
  the fins to the body
• Become limbs of amphibians during evolutionary
  descent

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Lung Fish Coelacanth
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Actinopterygii Ray-finned fish

• Thin, bony supports with radiating bones
• Filter feeders and predators
• Swim bladder- a gas-filled sac that regulates
  buoyancy and depth
• External fertilization
• Teleosts- 95 of all living fish
• Examples tuna, bass, perch, catfish, eels, and
  trout

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Trout, Swordfish, and Flounder
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Eel
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Class Chondrichthyes

• 850 species of skates, rays, and sharks
• Jaws, lots of teeth, paired fins, and a cartilage
  endoskeleton
• 5 to 7 gill slits on both sides of the pharynx
  lack gill covers

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Class Chondrichthyes- Sharks

• Teeth of sharks are enlarged scales
• Largest sharks are filter feeders (Basking and
  whale sharks)
• Most sharks are fast-swimming, open-sea predators

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Basking and Whale Sharks
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Class Chondrichthyes (Elasmobranchia)- Rays and
Skates

• Family Rajidae of the order Rajiformes
• Live on ocean floor
• Pectoral fins enlarged into wing-like fins
• Swim slowly
• Venomous spine
• Countershading- Bottom is lighter while top is
  darker
• Electric ray stun with over 300 volts
• Rays are live-bearing while skates are egg laying

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Sawfish
Sawfish rays have large anterior "saw" -use to
slash through schools of fish
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