This species of octopus is as unusual as it is beautiful. The argonauts, also known as paper nautiluses, spend their lives drifting near the surface of tropical and subtropical seas far from their cephalopod cousins on the seafloor. Females do this tucked into fragile, translucent shells that they create themselves.

Females are much bigger than males, about eight times larger and 600 times heavier. During mating, the male’s hectocotylus, an arm that contains sperm, is released and stays inside the female.

Without the nooks and crannies of the ocean floor in which to lay eggs, the female takes matters into its own tentacles. After mating, it begins secreting calcite from the tips of two of its arms, a continuous process. That