Vertebrate Zoology

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Vertebrate Zoology

• Agnatha
• Hagfish
• Lamprey

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Key Features

• Jaws are absent.
• Paired fins are generally absent.
• Early species had heavy bony scales and plates in
  their skin

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Key features cont

• In most cases the skeleton is cartilaginous. The
  embryonic notochord persists in the adult.
• Seven or more paired gill pouches are present.
• Hagfish sheds slime layer

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Key features cont

• A light-sensitive pineal eye is present.
• The digestive system lacks a stomach.
• External fertilization both ovaries and testes
  present in individual but gonads of only one sex
  functional in hagfishes, no larval stage
  separate sexes and a long larval stage in
  lampreys.

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Hagfish Classification

• Kingdom Animalia
• Phylum Chordata
• Class Pteraspidomorphi
• Order Myxiniformes
• Family Myxinidae
• Genus Myxine
• Species glutinosa

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Slime Glands
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Hagfish

• Hagfish can be found in chilly waters
• They tend to live on and in muddy sea floors in
  very dense groups (up to 15,000 in an area).
• Because females tend to produce large eggs in
  small numbers, their population sizes suggest a
  low death rate.

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Hagfish

• Diet is made up of marine worms and other
  invertebrates
• They have a ring of short sensitive tentacles
  around their mouths.
• Large slime glands line their sides along the
  length of their bodies.
• Can sneeze to clear slime from nostrils

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• No jaws. Instead they have two pairs of rasps
  on top of a tongue. They pull meat into their
  mouths with the tongue, then tear it off the prey
  with the rasps.

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Hagfish Anatomy
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• Hagfish have a very low metabolism. Once they
  eat, they may not have to again for up to seven
  months.
• Although hagfish have a partial skull, they have
  no back bone, so are not true vertebrates. What
  skeleton they do have is made of cartilage.

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Lamprey Classification

• Kingdom Animalia
• Phylum Chordata
• Subphylum Vertebrata
• Class Cephalaspidomorphi
• Order Petromyzontiformes
• Family Petromyzontidae

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Lamprey Dissection

• External
• Mouth
• Head Pharynx
• Heart
• Gonads

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