Greater Argonaut

The greater argonaut is an octopus that drifts near the surface of the open sea. Males of this species are about 2 cm in size, and females are about 25–30 cm in size. Females secrete calcium to form a thin, semi-transparent shell. They begin to create their shells during their juvenile stage, and the shell will grow bigger to match the growth of the body of the octopus; there they live and care for their eggs. The males do not have a shell and are very small in size.
The greater argonaut is thought to occur in tropical and subtropical waters worldwide. However, due to the small number of individuals being discovered, many aspects of this species remain unknown. However, it has long been known that they have been caught, alive, in pound nets (a set of nets set near the shore and used to interrupt the movement of target species that funnels fish into the trap).