The Weapon That Does Not Recognise the Clownfish
Nature · · 5 min read · By No Design Editorial
It is not armour and it is not slime. The anemone fires at a chemical signature, and the clownfish simply does not carry it.
The clownfish and the sea anemone look impossible on paper. The anemone's tentacles bristle with stinging cells that paralyse almost any fish brushing against them. The clownfish moves among them untouched, and in return drives off creatures that would nibble the anemone and enriches it with the nutrients in its waste.
The mechanism is worth stating precisely, because it is more interesting than 'the fish has protective slime'.
An anemone's stinging cells do not fire at just any contact. Firing needs two conditions met together: something has to touch the trigger, and the chemistry of what touched it has to read as prey. The cells respond to particular sugars, including sialic acids, carried on the surfaces of ordinary fish. The clownfish's mucus coat is unusual in lacking the compounds that would set the harpoons off.
So the fish is not armoured. It is chemically invisible. The weapon does not recognise it as a target.
That is recognition rather than resistance, and recognition requires a match between two chemistries owned by two unrelated species. A fish with the wrong surface chemistry is not stung slightly less. It is stung, paralysed and eaten.
'And We have placed in it, the earth, livelihoods for you and for those for whom you do not provide.' (Quran 15:20)
From Chapter 6: The Web of Life.
Tags: Mutualism, Chemistry, Recognition, Quran