How do nems know they are hosting a clown?

[Steph1]

I think we all know about the symbiotic relationship between the anenome and clowns.
But how does the anenome know it is a clown that they are hosting and not another species that the nem would otherwise sting and eat. What signal does the anenome get that it is a clown smuggling up to them? Is it chemical, behavioural..............?

 

[Steph1]

I found this very interesting, it seems the clowns become invisable to the anenome:
Interestingly, even clownfish that are innately protected exhibit this “acclimation behavior.” After initial contact, they acquire antigens from the anemone they have encountered. It has been proposed that these antigens serve as a type of “chemical camouflage” for the fish. With the acquisition of these antigens, the anemone is no longer able to distinguish between itself and the clownfish. The result is that the anenome no longer reacts to the fish by stinging.

This summary was contributed by Alexis Dean.

Source: https://asknature.org/strategy/mucus-coat-protects-from-sea-anemone/