The unnamed first-person narrator is a lonely, isolated man living in Paris. Seeking companionship and intellectual stimulation, he bypasses the zoo's lions and panthers to focus entirely on a tank of Mexican salamanders. He is highly empathetic and prone to obsessive observation, which begins to alter his self-perception and his understanding of reality.

The axolotl is a Mexican larval-stage salamander housed in a cramped enclosure at a Parisian aquarium. Characterized by its small Aztec-like face, tiny human-like fingernails, and lidless golden eyes, the creature appears largely immobile. To the narrator, these physical traits project both a mysterious intelligence and a profound sense of claustrophobia.

The aquarium guard is a practical, observant employee at the Jardin des Plantes. He represents the external, rational human world, acting as a clear contrast to the highly interior and obsessive narrator. He monitors the public viewing areas and attempts to maintain normal boundaries between the visitors and the animals.