(source of photo here)
The blanket octopus (Tremoctopus violaceus) pictured is a female. The males and females of this species are very different in size. Australian and British marine biologists stumbled across the diminutive male octopus while scuba diving in the Great Barrier Reef. Divers spotted a male 2.4 centimeters (0.9 inches) long. By contrast, females of the species grow up to two meters (6.6 feet) long. Blanket octopuses are rarely seen. They spend their entire life drifting in the open oceans of warm regions worldwide. When a male blanket octopus encounters a female, he fills a modified tentacle with sperm, tears it off, presents it to its prospective mate, and then drifts off to certain death. The female blanket octopus uses her unique feature as a most impressive defense mechanism. Instead of using ink to scare off predators, the female (when threatened) will unfurl her large net-like membranes which billow gracefully in the water behind her. This “blanket” greatly increases her apparent size.