Marine Fishes

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Marine Fishes

• Read Chapter 9 Pages 154- 178

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Chordates

• All chordates have (at least during some period
  of their life)
• Dorsal nerve cord
• Gill slits
• Notochord
• Post-anal tail
• These are the 4 basic characteristics of all
  chordates.

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Bridging the gapChordates w/o backbone

• Tunicates
• Not fish but chordates
• Lancelets Not a Vertebrate, but a Chordate
• Chordate characteristics throughout life-
• But no backbone
• Subphylum Cephalochordata

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The Fishes

• Note The term fish refers to a single fish or a
  group of the same species of fish.
• Fishes refer to more than one species of fish.

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Fish

• Structurally simplest living vertebrates
• Probably 30,000 species
• At least half of all known vertebrate species are
  fishes
• At least half of all known fishes are marine
• First appeared about 500 million years ago and
  were the first vertebrates
• every other vertebrate has ultimately descended
  from a fish-like ancestor

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Three major groups of Fish

• Jawless fishes (Agnatha)
• Cartilaginous fishes (Chondrichthyes)
• Sharks and rays (elasmobranchs)
• Ratfishes (chimeras) (Holocephalins)
• Bony fishes (Osteichthyes)
• Lobe-finned fishes
• Ray-finned fishes

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Jawless Fishes

• Most primitive living fishes
• Feed by suction with a round, muscular mouth and
  rows of teeth
• Long, cylindrical body
• No paired fins or scales
• Lampreys are parasites on other fishes and suck
  on their blood hagfish typically feed on dead
  animals

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Jawless Fish
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Cartilaginous Fishes

• Sharks, rays, skates, chimeras (ratfishes)
• Skeleton is made of cartilage, which is lighter
  and more flexible than bone
• Moveable jaws with well-developed teeth
• Paired lateral fins for efficient swimming
• Rough skin due to placoidscales

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Sharks

• In some form, sharks have been around for about
  400 million years.
• Even before dinosaurs roamed the earth, sharks
  hunted through the oceans! They're such good
  survivors that they've had little need to evolve
  in the last 150 million years.
• Scientific Information Sharks belong to the
  class of fish, Chondrichthyes.
• More on Sharks to come in a later lecture!!!

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Skates vs. Rays

• Skates
• Oviparous (lay eggs)
• Mermaids purse
• Do not have barbs, have thorns on their dorsal
  area or tails
• Placement and number vary
• Small teeth

• Rays
• Viviparous (bare Live young)
• Have Barbs
• Above tail
• In general, larger
• Tail almost 2xs as long as body
• Plate Like Teeth

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Skates and Rays

• Flattened body
• Large pectoral fins

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Rat Fishes (Chimeras)

• Bizarre-looking, primarily deep-sea,
  cartilaginous fishes
• Have only one pair of gill slits instead of 5-7
• Have a long rat-like tail
• Feed on crustaceans and molluscs

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Cartilaginous vs. Bony Fish

• Cartilaginous
• skeleton made of cartilage
• possess movable jaws mostly with powerful teeth.
• mouth is located ventrally (under the head).
• presence of paired lateral fins allows for
  efficient swimming.
• skin is covered with small scales that have the
  same composition as teeth.

• Bony
• Skeleton made (at least partially) of bone
• Thin, flexible, overlapping scales along the body
  
• A flap of bony plates and tissue known as the
  gill cover, or operculum, that protects the gills
  
• Protruding jaws with more freedom of movement
  than cartilaginous fish
• The presence of a swim bladder
• helps buoyancy and compensates for the relatively
  heavier bony skeleton
• Highly maneuverable fins

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Cartilaginous Vs. Bony External
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Cartilaginous vs. Bony
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Cartilaginous vs. Bony
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Cartilaginous vs. Bony
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Cartilaginous vs. Bony
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Extinct No More

• Subclass Sarcopterygii-Once known only for
  fossils and thought to be extinct for 60 million
  years-Named Latimeriachalumnae
• Preserved specimen of the Coelacanth is located
  in the HMNH

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Next Up

• Fish Form and Function