Three hearts and blueish green blood… 10 fun facts about cuttlefish

Many divers here in Dauin want to see cuttlefish, whether it is big or small, swimming or hiding. We are lucky to have a few that frequent our house reef, as well as some other dive sites where they are quite common. These critters are surely one of the weirdest here on the coast, but there is more to them than meets the eye. Here are ten awesome facts about cuttlefish.

1. Cuttlefish are cephalopods, meaning head-foot, and closely related to octopus and squid. They contain a cuttlebone to regulate their buoyancy. Cuttlebones are also fed to pet birds to increase their calcium intake.
2. Cuttlefish can be found all over the world in tropical and temperate oceans except for the Americas. It is thought that cuttlefish never made it to the Americas because the North Atlantic Ocean became too cold and deep. Many dive and snorkel operators in the Caribbean tell their guests they see cuttlefish, but in reality they are Caribbean reef squid which closely resemble cuttlefish when they swim.
3. Jet Propulsion!!! For fast movement, cuttlefish use their siphon to expel water from the mantle cavity. They also have a fin that encompasses their entire mantle (body) which are used for steering, stabilization, and also slow movements.
4. Cuttlefish eyes are fully developed before they have hatched from their eggs. They can even change color in reaction to outside stimuli! It is thought that baby cuttlefish begin hunting prey while still in the egg, tracking movements of small fish and crustaceans, and prefer the prey that they see during this time.
5. Cuttlefish have three hearts and blue-green blood. One heart is for the whole body while the other hearts are for each set of gills. The blood is blue-green because it carries a copper-containing protein in its blood instead of an iron-containing protein.
6. Cuttlefish are referred to as the “chameleons of the sea” due to their color-changing abilities. They can do this even though they are completely color blind. They can even successfully change color to match their surroundings in complete darkness. Some species use disruptive patterning, breaking up their outline, while others blend in to their surroundings. This is all done by cells in their skin called chromatophores, with different kinds relating to yellow, red/orange, and black/brown. These cells can be used independently or together to produce different colors and patterns.
7. During mating season, male cuttlefish change color to attract mates. There is even video of a male cuttlefish with half of his body displaying a flirting color to the female on one side, with the other half of his body displaying an aggressive color to ward off the male on the other side. That’s some serious multitasking! Some males have discovered a better way to find a mate using color change. These males change their coloration to represent a female, tricking the males into a false sense of security, and then quickly mating with their female behind their back. This is called a ‘sneaker male.’
8. Sepia, a popular ink color, is derived from cuttlefish. Like octopus, cuttlefish have an ink sac from which they can expel ink when in danger or to confuse an enemy. This ink was once used for the color sepia but now they use artificial dyes.
9. Cuttlefish have crazy eyes. They have a W-shaped pupil and use their lenses completely different from mammals. Their eyes can even detect differences in polarization. Instead of the lens changing shape, cuttlefish shift their lenses forwards or backwards to change focus. Believe it or not, they can even see backwards!
10. Flamboyant cuttlefish are insane. Their muscle tissues contain a highly rare and potent toxin that scientists don’t fully understand yet, which is why they display such amazing colors. They have also lost the need to swim away from predators, so they are bottom dwellers. Using their two biggest arms as ‘front legs’ and changing the texture of their mantle to create two ‘back legs.’

Chameleons of the Sea

If you’ve never seen one of these amazing critters, or if you want to see more, come dive with us here at Atmosphere! There is always a good chance of seeing cuttlefish here in Dauin.

Your marine biologist

/Daniel