Fish: Class Agnatha and Chondrichthyes

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FishClass Agnatha and Chondrichthyes

• November 13, 2007

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Vertebrates

• What are the properties of vertebrates?
• Belong to the Chordates
• Vertebral column (spine, backbone)
• spine protects nerve cord
• the brain is at the anterior end of the spinal
  cord, protected by skull

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Fish
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Class Agnatha

• Jawless Fish
• No Jaws
• Unpaired fins and no scales
• 2 Major Groups
• Hagfish
• Lampreys

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Class Agnatha

• Hagfish
• 60 species
• Lack any trace of vertebrae
• Scavengers
• Secrete mucous

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Class Agnatha

• Lampreys
• 40-50 species
• About a meter long
• Single nasal opening
• Large, well-developed eyes
• Parasitic

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Class Agnatha

• Lampreys
• almost all are anadromous
• females produce hundreds to thousands of eggs

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Class Chondrichthyes

• Cartilaginous fish
• Flexible, cartilage skeletons
• Movable jaws
• Paired and unpaired fins
• 2 Groups
• Holocephali (Chimeras)
• One gill opening on each side of the head
• Elasmobranchii (Sharks, Skates, and Rays)
• Multiple gill openings

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Holocephali

• Chimeras or Ratfish
• 34 species
• Usually not over 1 m. in length
• Usually found deeper than 80 m.
• Move into shallow water to lay their eggs
• Most feed on shrimp, mollusks, and sea urchins
• Swim by undulating the body to wave the tail and
  by fluttering their fins

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Sharks

• 360 species
• 2 groups
• Squaloids
• 80 species
• Includes dogfish, basking shark, and megamouth
• Usually live in cold, deep water
• Galeoids
• 280 species
• Includes nurse shark, horn shark, whale shark,
  great white, and hammerheads
• The dominant carnivores of shallow, warm waters

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Sharks

• General body shape

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Sharks

• Size range
• Average 2 m. long
• Smallest shark - 25 cm.
• Deepwater Dogfish
• Largest shark - 60 m.
• Whale Shark

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Sharks

• Skin
• A unique armor made up of placoid scales
• What is the benefit to having these scales?

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Sharks

• Senses
• Olfaction
• Mechanoreception
• Vision

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Sharks

• Ampullae of Lorenzini - Extra Sense

http//faculty.uca.edu/benw/biol4402/lecture7a/sl
d008.htm
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Sharks

• Adaptations For Feeding
• Jaws
• Cranial Kinesis
• Shark teeth

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Sharks

• Reproduction
• Internal fertilization
• Reproduction strategy?
• Modes of Reproduction
• Oviparous
• Ovoviviparous
• Viviparous

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Sharks

• Social behavior
• Commercially hunted

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Skates and Rays

• More diverse than sharks
• 456 extant species
• Probably evolved from the Squaloid sharks

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Skates and Rays

• Adaptations
• Shape
• Color
• Pectoral Fins
• Electric Impulses

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Skates and Rays

• Diet
• Most eat benthic invertebrates
• The largest are plankton strainers

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Skates and Rays

• Differences Between Skates and Rays
• Tail
• Skates have an elongate thick tail with 2 dorsal
  fins and a terminal caudal fin
• Rays have a whip-like tail, and their fins are
  replaced by one or more enlarged, serrated, and
  venomous barb
• Mode of Reproduction
• Skates are oviparous
• Rays are viviparous