The Ultimate Size Difference
Female blanket octopuses are 40,000 times heavier than males — the most extreme size difference of any non-microscopic animal.
The blanket octopus holds the record for the most extreme sexual size difference of any animal you can see with the naked eye.
Females can grow over 6 feet long and weigh up to 40,000 times more than males. Males are walnut-sized — about 1 inch long.
This extreme dimorphism evolved because males and females face completely different survival pressures: - Females need to be large to carry and protect eggs - Males only need to be big enough to produce sperm and find a female - Smaller males may be harder for predators to spot
Like other octopuses, male blanket octopuses have a specialized arm called a hectocotylus that stores and delivers sperm. But in blanket octopuses, this arm breaks off during mating and stays with the female.
Females have another remarkable adaptation: they're immune to the stings of Portuguese man-of-war. Young females rip off man-of-war tentacles and wield them as defensive weapons, whipping them at predators.
Despite their dramatic appearance (females trail long, flowing "blankets" of webbing), blanket octopuses are rarely seen. They live in the open ocean, far from shore, making them mysterious even to scientists.