provided by World Register of Marine Species
The argonauts or paper nautiluses (a misnamer, use of which must be discouraged) are very abundant in tropical to warm-temperate waters of the world. A large number of nominal species exists, but the group needs revision to verify the species, perhaps 6 to 8 in all. The family is monotypic. The "shell", actually in incubation chamber for the eggs, is popular among collectors because of its beauty, coloration, sculpture and fragility. The largest species, Argonauta argo, attains a maximum size of nearly 30 cm shell diameter, it enters fish markets in India and Japan when fortuitous oceanographic conditions cause mass aggregations so that large numbers can be captured. Normally it is non-schooling, solitary group. Sexual dimorphism very marked, with adult females relatively large, up to 10 to 15 times larger than adult males; hectocotylus of males autotomous (self-amputating) into the egg mass that is attached inside a large, external, calcium carbonate egg case ("paper nautilus shell") in which the female also resides, holding on to the case with extremely broad webs on the dorsal arms (l); suckers biserial; web weakly developed; no water pores; no shell vestige.
- WoRMS Editorial Board