Brain root coral
Most coral colonies remain connected by a living tissue and they will share nutrients and other important proteins across this tissue. The individuals of this brain coral separate completely but in a chemical language hidden from us they can talk to each other. If one of them is being attacked by a sponge for example, the others will sense their brother (or sister, or both) is in trouble and will send weapons (toxic chemicals) to them.
They do this by placing the chemicals in mucous and releasing it (sort of like making a very long strand of energy-giving snot dribble out of your nose until it is caught and sucked up by someone else).