• Jaejeong & Jaeah Kim

A Dramatic Exit: Cephalopod Ink

We have done both a squid dissection (which you can check out here), and an octopus dissection (which you can check out here), where we explained the anatomy and physiology of these fascinating cephalopods. Now one fascinating trait cephalopods share is their ability to ink. All cephalopods (except Cirrina & Nautilidae) possess a unique defense mechanism where they eject clouds of jet black ink from the ink sacs within their bodies.

So why do cephalopods ink? Well, despite the obvious reason of obscuring the attackers vision with the pitch black substance, studies have observed that there is a second inking behavior often engaged by many species of cephalopods. Another reason cephalopods ink is to confuse the predators– many species of cephalopods are able to produce an ink ‘pseudomorph’ (ejections that resemble the form of a cephalopod) in order to confuse the predators, earning them the time to escape. What’s fascinating is that cephalopods are able to control the amount, direction, speed, and even mucous concentration in their ink ejections– the reason pseudomorphs hold their shape is due to the fact that such projections often have a much higher mucous concentration. Select species of cuttlefish are even able to release thinner streams of ink called ‘ropes,’ that resemble the tentacles of a jellyfish, deterring predators. Last but not least, Heteroteuthis dispar, a species of squid, ejects bioluminescent bacteria containing mucus rather than ink, using flashing lights instead of darkness to disorient predators. (You can check out this article on our website, where we go into much more detail about these fire-shooting squids).

Although many people think cephalopod ink is similar to regular pen ink or printer ink, that is not that case. The main chemical constituents of cephalopod ink is melanin and mucous, but it also contains smaller amounts of other chemicals such as dopamine, tyrosinase, L-DOPA, and amino acids (taurine, glutamic acid, lysine, alanine, and aspartic acid). Out of all these, tyrosinase is known to numb, irritate, or even deactivate the chemosensory systems of the cephalopods’ predators. In fact, the tyrosinase found in cephalopod ink is so potent that octopuses who don’t escape their own cloud of ink can die. If that wasn’t menacing enough, blue-ringed octopuses (Hapalochlaena lunulata) are able to excrete tetrodotoxin (a deadly neurotoxin) along with its ink.

Cephalopod ink has numerous uses for us humans– squid ink has been used in the past for writing, and cephalopod ink is used in culinary settings in many countries such as Greece & Japan to this date. If you haven’t tried squid ink risotto, it’s actually surprisingly delicious. Besides that, studies suggest that oral consumption of cephalopod ink may have anti-tumor properties, and thus further research into cephalopod ink may yield great scientific discoveries. Who knew?


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