xeno- (from a foreign or strange place) + genesis (the origin, start or point at which something comes into being)
According to the authoritative guide to classical sea creatures, A Glossary of Greek Fishes, the pinna (a type of oyster) and the pinna-guard (a crawfish) were seen to live together in perfect symbiosis: “Opening its shell, the pinna remains immobile, looking for whatever little fish might enter. The pinna-guard informs it whenever anything enters by biting it, as if making a sign; and once bitten, the pinna closes. It is thus that the pinna and the pinna-guard together eat whatever remains imprisoned on the inside” (as cited by Daniel Heller-Roazen, 2009)
Through the pinching of its flesh the oyster comes to know itself as does the crawfish who does the biting, when his pincers touch the fleshy insides of the marine mollusk whenever the crawfish becomes aware of the little fishes swimming into the oyster’s waiting mouth.