“Tentacles” Basic Facts

What exactly is a cephalopod?

  • A mollusk, related to snails, clams, mussels and sea slugs. Common body structure including: bilaterally symmetrical body, a mantle which acts as a skin-like covering, three hearts, blue blood (when exposed to air), file-like tongue called a radula, a head surrounded by a ‘foot’ which has evolved into arms and/or tentacles.
  • More than 800 species of cephalopods have been identified so far; scientists suspect there may be as many as 1,000.
  • Difference between octopuses, squid, nautiluses and cuttlefishes
    • All species except the nautiluses have suckers on their tentacles and arms
    • Octopus don’t have tentacles, they only have arms
    • Squid and cuttlefishes have eight arms and two retractable tentacles
    • Nautiluses are one of only a few cephalopod without an ink sac
    • All cephalopods, except nautiluses, have acute vision that they rely on to avoid predators and detect prey.
    • All octopuses and most other cephalopods are color blind – surprising considering they are adept at changing colors.

A Closer Look

  • Nautiluses
    • Have head and eyes, mantle and siphon, beak and radula, no ink sac and up to 100 tentacles without suckers.
  • Squid
    • Have head and eyes, mantle and siphon, beak and radula, an ink sac and eight arms with two tentacles with suckers; some squid species have hooks on their arms and serrated “teeth” in their suction cups.
  • Octopuses
    • Have head and eyes, mantle and siphon, beak and radula, an ink sac and eight arms with one or two rows of suckers but no hooks or sucker rings.
  • Cuttlefishes
    • Have head and eyes, mantle and siphon, beak and radula, an ink sac and eight arms with two tentacles with suckers.