He never gives them up. And every time he moves to a larger shell, he takes care to prepare an adequate accommodation in the new home also for his faithful traveling companions. And life companions. The only ones with whom he agrees to share the “domestic” space in which he notoriously does not like intrusions, not even from his peers.

It is no coincidence that, together with the recovery shell adapted from time to time to the new measurements of its growing body, the Paguro Bernardo carries with it that nickname of “hermit” borrowed from its solitary existence. The only exceptions are the anemones anchored on its shell, belonging to the species Calliactis parasinica, which for this consolidated symbiosis is naturally associated with the Pagurus bernhardus.

Community life, the result of a long and complex adaptation, has advantages for everyone. For the hermit crab, which always carries them with it, those polyps represent a precious life-saving protection. Sea anemones, in fact, are cnidarians, anthozoans, hexacorals. Cnidarians, as they have stinging cells that, placed on white filaments called acontia, come out as soon as they are attacked by predators. In this way, the anemones defend themselves and also the hermit crab that hosts them. Furthermore, their presence on the shells, favors their camouflage on the seabed, helping the hermit crab to hide more effectively from its attackers.

Even for sea anemones, the advantage of cohabitation is notable. First of all, thanks to the hermit crab that carries them on its shell, they can move around without any effort and with movement they have a greater chance of feeding. And then they can always make use of the leftovers from their host's meals. The host really takes care of them, willingly accepting their presence on the shell in which it is installed. And furthermore, every time it is forced to change it, it takes care to move one by one the anemones it lives with onto the new shell. Bernardo and his anemones are one of the most astonishing examples of mutualistic symbiosis that is established between the inhabitants of the sea depths.