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Octopuses are common in the seas around our coast, and indeed not too unusual on our dinner plates.
But few of us give them a passing thought, generally writing them off as ugly, slimy creatures – the stuff of horror stories, films and video games.
Along with squid, nautiluses and cuttlefish, octopuses belong to the cephalopod class of the mollusc family, and as such they have a remarkable and unique body plan.
For instance they sport three hearts and nine brains – one for each limb and a central co-ordinating centre (1) – they can change the colour of their skin in an instant, produce a toxic ink to out-fox predators, and they move by jet propulsion.
What’s more, they are highly intelligent animals which can use tools and solve mazes.
Octopuses are well adapted to their ecological niche, the sea floor, where the dark and watery environment inhibits the use of traditional sense organs like eyes, nose and tongue, for surveying their surroundings.
Instead they utilise their eight flexible arms, each with its own brain, to inform their foraging and detect prey – mainly crabs, fish and snails.
Octopus arms bear rows of suckers that provide a ‘touch-taste’ sense, allowing the animals to identify chemicals from, and the movement of, potential prey.
On land most of the chemicals signals we detect are airborne, many of which are not soluble in water, so would perhaps go undetected by octopuses.
Recently though, scientists have uncovered the molecular details of how octopuses perceive these insoluble chemicals (2).
It turns out that octopus suckers are complex structures that contain specialised cells called chemoreceptors for detecting soluble chemicals and others called mechanoreceptors for detecting non-soluble substances.
These cells transmit specific electrical patterns encoding chemical and touch information to the related brain where it is decoded to give a detailed picture of the animals’ surroundings.
These findings begin to explain how the unique and complex body plan of the octopus with its eight limbs, each bearing chemoreceptors connected to a local brain, is so well suited to the animals’ sophisticated behaviour, and gives them a predatory advantage in their particular environment.
(1) Gavin Cooke, British Wildlife, Dec 2020.
(2) van Giesen L et al. Cell 183, 594-604. 2020.