The Atlantic Pygmy Octopus, scientific name Octopus joubini, also known as the Small-egg Caribbean Pygmy Octopus, is a tiny species of octopus. Fully grown, this cephalopod reaches a mantle length of 4.5 cm (1.8 in) with arms up to 9 cm (3.5 in) long.
The Atlantic Pygmy Octopus often seeks shelter from predators in empty clamshells, beer cans or small openings, pulling the opening closed with its arms, combining sand and gravel to form a lid. The Atlantic Pygmy Octopus employs the two defensive mechanisms typical of all octopuses: ink sacs and camouflage.
Like all octopuses, Octopus joubini is carnivorous. It is able to bore into the hard shells of small clams or other creatures and, after secreting its poisonous saliva to paralyze its victim, eats its prey. While the Atlantic Pygmy Octopus feeds primarily on small crustaceans, only a few species have been recorded as prey of this species in the wild. In laboratory conditions this diet is expanded considerably.
Females of this species brood between March and June, laying elliptical amber eggs in a sheltered place. The hatchlings are relatively small (0.04 g), but are fully formed and can hunt within hours. They reach maturity in around 182 days and weigh about 30 g at this time.