Cuttlefish A Lot Going On For What Is Essentially A Slugs Cousin
Cuttlefish belong the to the mollusc family and look like something between an octopus and a squid. Unlike most molluscs, the cephalopod branch which includes cuttlefish, squid and octopus are fairly smart. Certainly compared to their simpleton slug cousins but as with all geeks there comes weirdness – lots of weirdness.
Three Hearts & Blue Blood
Let’s get the ball rolling with this cardiovascular indulgence. Cuttlefish have three hearts, one each for their two sets of gills and one for the rest of the body. The blood that is pumped around is blue/green in colour. Cuttlefish blood carries a copper containing protein as well as the iron containing protein that red blooded animals have. So probably a good idea to stay away from cuttlefish during lightning storms.
Largest Brain To Body Ratio Of Any Invertebrate
To be fair that’s not much of a boast, the competition is fairly weak. Cuttlefish are at times social animals, they use chemicals and colour changes to communicate with each other. Male cuttlefish have been seen to display a flirty display to a female on one side of its body and threat displays to a rival male on the other side. They also use different tentacle positions to communicate and have been seen to respond to humans imitating these postures. A kind of sign language but nobody has the faintest idea what the other is saying.
In laboratory tests they’ve solved maze puzzles quite easily. Comparing intelligence of an animal from a completely evolutionary tree from us is not easy and the cuttlefish probably think the scientists are fairly dense for giving it free food everyday.
Well kinda. We’ve already covered how cephalopods use chromatophores to change the colour of their skin in an octopus article. Underneath the 200 chromatophores per square mm they have other cells called leucophores which scatter light making the skin appear white (similar to polar bear fur, their skin is actually black). They will also reflect what ever colour the ambient light is, that’s why it appears white near the surface but will turn blue or green as they go deeper. If you have colour filters for your torch maybe you can try and shine it on a cuttlefish next time you see one.
Cross Dressing Sneaker Males
So yeah, in the cuttlefish world if your not blessed with genes that make you big, strong and aggressive the males have little chance to to breed or so you would think…In some species some males don’t grow very large and employ a different tactic to get some action. The smaller or ‘sneaker’ males mimic the colours and tentacle patterns of the females. Just like cross dressing human males they also have to hide the extra package. Males have a modified tentacle that delivers the sperm. The sneaker males are wily enough to keep it hidden. So effectively they slip on a dress, slap on some lippy and tuck away the bulge to sneak past the larger more aggressive males to mate with the females. They can secure up to a third of all successful matings.
You’d think that being able to instantly change colour, squirt clouds of ink and dazzle predators with light shows would be enough but no the cuttlefish has one more trick up its sleeve. The syphons on each side of the cuttlefish release a small electrical field that is enough for sharks to pick up. When the cuttlefish detects the looming silhouette of a shark or other large predator it will freeze in place, cover the syphons with it’s tentacles and clamp down on it’s mantle. Reducing it’s electrical field by as much as 80%, hoping that the shark will swim on by. It doesn’t always work but that’s life…
Cuttlefish have plenty of survival techniques but they do need them? After all they’re just a big protein filled bag with arms and no real defence apart from camouflage. If one of their ten appendages does get bitten off, it can be completely regrown in as little as 40 days.
The flamboyant cuttlefish has taken itself off the menu by having incredibly toxic proteins in its flesh. Loud colours tell everyone to steer clear. It’s been so effective that this tiny animal just walks around on the bottom without a care in the world like a miniature psychedelic tank.
Gonna Rule The World
There are about 120 known species of cuttlefish in our oceans and they reside in many different locations. Although there’s no species present in the America’s as far as we know. They were around before fish evolved and trees grew on land and with the present overfishing of our oceans the biomass of cephalopods is thought to be more than at anytime in recent history. Their quick growth rates and short life spans (1 – 2 years) enable them to re populate areas faster than slower growing species – like weeds vs trees.
They Have An Inbuilt BCD
The shell that many molluscs use for protection has been ditched by many of the cephalopod family in favour of speed and manoeuvrability. However the cuttlefish contain remnants of the shell internally and use it to control their buoyancy. The ‘cuttlebone’ has hollow chambers that can be filled with gases to help maintain position.
You will probably have seen a cuttlebone either washed up on the shore or jammed between the bars of a birdcage. The pet birds use it to keep their beaks sharp and as a source of calcium. Who would of thought that parrots are responsible for so many cuttlefish deaths.
The W shaped pupils of a cuttlefish may look strange to us but they’re highly effective. Although surprisingly considering their amazing camouflage abilities, cuttlefish are thought to be colour blind. Although new research suggests maybe they see colours but just in a different way from us. They can definitely see polarised light and adjust their camouflage based on this.
The w shaped pupil runs the whole length of the eye enabling cuttlefish to see what’s behind them as well as what’s in front. Another very handy survival tool.
Still On The Menu?
Cuttlefish are apparently quite tasty and are often seen on menu’s, especially in Asia. After interacting with one of these incredible creatures I’m sure you’ll never want to eat one again.
We can find them on all of our dive sites but Shark Point and Richelieu Rock are particular popular especially for mating.
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