Cephalopods are members of the Mollusca phylum and include such marine creatures as squid, cuttlefish and octopus. The name “cephalopod” comes from the Greek and roughly translates as “head-feet,” which I’m sure we can all agree pretty much sums up the appearance of these creatures.
You’ll find cephalopods in every ocean and in all depths, right down to the Abyssal plain between 9,800 and 19,600 feet. They’re most abundant along the equator. A cephalopod sighting always promises a great encounter and photo opportunity; here are 13 facts to impress your dive buddies with the next time you see one.
1. There are around 800 living species of cephalopod. Amateur fossil hunters frequently find extinct species, such as ammonites.
2. They are complex and intelligent, with well-developed senses, nervous systems and large brains. Cephalopods are considered the most intelligent of all invertebrates.
3. Octopuses possess great vision; experiments have shown that they can distinguish attributes of various objects, including brightness, size, shape, and horizontal or vertical orientation. Yet most are also color blind.
4. They can detect gravity using a sensory receptor called a statocyst. Some are even thought to use the receptor to detect sounds.
5. Cephalopods are older than dinosaurs, appearing in fossil records 500 million years ago.
6. Even though they are color blind, most cephalopods can camouflage themselves with the surrounding environment. They do so using chromatophores, pigment-containing and light-reflecting organelles found in their cells. These change color by expanding or contracting. Not only can they change color but also texture.
7. These skills are not just for camouflage; cephalopods also change colors and textures when trying to warn others off or while trying to attract a mate.
8. Fins and tentacles are usually a cephalopod’s main forms of propulsion, with jet propulsion used for sudden bursts of speed. The larger the cephalopod, the less efficient its jet propulsion skills.
9. The largest octopus is the North Pacific giant octopus (GPO), which can grow to be almost 15 feet long.
10. The largest squid is the colossal squid, but not much is known about this species as it lives deep in the oceans. Some dead specimens, thought to be juveniles, have the largest eyes in the animal kingdom.
11. Even the giant squid is very rarely seen.
12. For comparison, the Australian giant cuttlefish, which is the largest cuttlefish, only grows to around 20 inches.
13. Octopi, octopodes or octopuses? All three names are commonly acceptable for the plural, but octopuses is the one used most, including in scientific writing. From an etymological point of view, octopi is incorrect, as -i indicates a Latin plural and octopus comes from ancient Greek where the plural is octopodes. The confusion arises from 18th-century scientific classification, which uses Latin, but borrowed the word from Greek.
