[6] Cephalopoda

• 2 Major Groups:

  1. Nautiloids (Nautilus)
  2. Coeloids (Squid, octopus, cuttlefish)
• General cephalopod characteristics:

  • Head-foot, tentacles attached to head
  • Active marine predators
  • Use one huge siphon to propel themselves through the water
  • Have tentacle limbs with suckers
  • Secrete nacre (Nautilus)
• The nautilus has a chambered shell

  • Each chamber is separated by the septa
  • Each chamber is connected to the body by the siphuncle
  • Gases in the chambers can be regulated, regulates buoyancy
• Nautiloids can have up to 90 tentacles surrounding its mouth
• Food storage in Nautiloids


  Crop
• Nautiloids move shell first, Coleoids move head first
• Coleoids

  • Very diminished shells (only pen or beak)
  • Very big eyes that can visualize images
  • Ink sac that produces the sepia
• Degenerate shells in Coleoids:

  • Squids - Pen
  • Cuttlefish - Cuttlebone
  • Octopi - no hardened structure
• Cephalopod adaptations:

  1. Ink sac
  2. Sophisticated skin pigments
  3. Chromatophores
  4. Iridophores
  5. Leucophores
  6. 3. Advanced nervous systems
• The mimic octopus (Thaumactopus mimicus) uses leucophores to mimic sea snake coloration
• The blue-ringed octopus (Hapalochlaena maculosa) has iridophores to warn predators of its toxicity
• Iridophores create iridescent colors, warning predators

  Leucophores mirror back the colors of the environment, making the animal less conspicuous
• Appendages in Coleoids:

  1. Squids - 10 appendages, all called arms, modified reproductive arm
  2. Cuttlefish - 10 appendages, 8 heavy arms, 2 larger tentacles
  3. Octopi - 8 appendages, all called arms, no tentacles, no teeth on suckers
• Arms have suction cups from beginning to end

  Tentacles only have suckers at the end
• Squids have a modified arm that delivers a package of sperm called the spermatophore to the female's oviduct
• Members of genus Argonauta lay eggs in delicate egg shells secreted by a modified tentacle