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Fish: Class Agnatha and Chondrichthyes

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Title: Fish: Class Agnatha and Chondrichthyes


1
FishClass Agnatha and Chondrichthyes
  • November 13, 2007

2
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

3
Fish
4
Class Agnatha
  • Jawless Fish
  • No Jaws
  • Unpaired fins and no scales
  • 2 Major Groups
  • Hagfish
  • Lampreys

5
Class Agnatha
  • Hagfish
  • 60 species
  • Lack any trace of vertebrae
  • Scavengers
  • Secrete mucous

6
Class Agnatha
  • Lampreys
  • 40-50 species
  • About a meter long
  • Single nasal opening
  • Large, well-developed eyes
  • Parasitic

7
Class Agnatha
  • Lampreys
  • almost all are anadromous
  • females produce hundreds to thousands of eggs

8
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

9
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

10
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

11
Sharks
  • General body shape

12
Sharks
  • Size range
  • Average 2 m. long
  • Smallest shark - 25 cm.
  • Deepwater Dogfish
  • Largest shark - 60 m.
  • Whale Shark

13
Sharks
  • Skin
  • A unique armor made up of placoid scales
  • What is the benefit to having these scales?

14
Sharks
  • Senses
  • Olfaction
  • Mechanoreception
  • Vision

15
Sharks
  • Ampullae of Lorenzini - Extra Sense

http//faculty.uca.edu/benw/biol4402/lecture7a/sl
d008.htm
16
Sharks
  • Adaptations For Feeding
  • Jaws
  • Cranial Kinesis
  • Shark teeth

17
Sharks
  • Reproduction
  • Internal fertilization
  • Reproduction strategy?
  • Modes of Reproduction
  • Oviparous
  • Ovoviviparous
  • Viviparous

18
Sharks
  • Social behavior
  • Commercially hunted

19
Skates and Rays
  • More diverse than sharks
  • 456 extant species
  • Probably evolved from the Squaloid sharks

20
Skates and Rays
  • Adaptations
  • Shape
  • Color
  • Pectoral Fins
  • Electric Impulses

21
Skates and Rays
  • Diet
  • Most eat benthic invertebrates
  • The largest are plankton strainers

22
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
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