Blue-ring octopus Mimic octopus a diffuse cloud, discrete objects called pseudomorphs and thinner‘ rope’ forms.
The form of inking may therefore be specific to the type of predatory attack experienced by the cephalopod. Cephalopods that ink pseudomorphs follow with escape behaviours whilst those that ink rope and cloud forms favoured a tactic called crypsis – swimming next to the ink to hide rather than actively escaping. This means, incredibly, that cephalopods may have full control of their ink, balancing the concentration of each secretion to suit the situation!
Ink is no deterrent for some species. The Indo-Pacific bottlenose dolphins have learnt to de-ink cuttlefish after capture and before eating.
“ We have used cephalopod ink for centuries( and still do) in cooking, traditional and modern medicine and as ink for writing and artwork”
Cephalopod ink is typically non-toxic, the blue-ringed octopus being one known exception. This species is notorious – look but don’ t touch. Its saliva contains tetrodotoxin( TTX) a toxin produced by a symbiotic bacterium; one bite is enough to kill. Interestingly, its ink also contains TTX, yet little research has been done to test why.
We have used cephalopod ink for centuries( and still do) in cooking, traditional and modern medicine and as ink for writing and artwork. The name given to ink is sepia, named after the Scientific name for cuttlefish. In 2009 the fossilised ink sacs of a Jurassic cephalopod were extracted: the ink was so well preserved it was used as sepia to draw a picture of the fossilised squid it came from – that’ s quite poetic.
Sea hares ink in an entirely different way to cephalopods. They also release two substances from specialised glands, but these are situated in the mantle cavity( a space within a layer of specialised tissue that protects the internal organs). These chemicals are a purple ink called aplysioviolin and a white opaline fluid. They can be used separately as a mild initial warning, but mixed together they produce hydrogen peroxide( acid!) an excellent chemical deterrent.
Rather than create ink products in their cells like cephalopods, sea hares obtain ink from the food they eat. Aplysioviolin is a photosynthetic pigment of red seaweed. If you were to remove this food source, and over time the sea hare will lose its chemical advantage. In the UK you may chance upon sea hares( Aplysia punctata) in rockpools. You may not even notice them but you’ ll certainly spot the bright purple stains covering your clothes after! �
Common cuttlefish under Swanage Pier
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