Instead of wasting time growing to maturity, the best strategy is to start searching for mates as early as possible, Tregenza said.Ĭontrary to males, however, female blanket octopuses may benefit from being large. Greater size, therefore, doesn't offer males any significant advantage in tracking down a female mate. The male octopuses' chances of finding a mate 'are in the hands of fate,' said Tregenza. Some of the most extreme examples of size differences between the sexes come from marine and parasitic animals, where males find it difficult to locate females. The largest females of the species are almost twice as long and are likely to weigh as much as 10 kilograms (27 pounds), almost 40,000 times as heavy. Later comparison with museum specimens revealed the unusual nature of the find.Ī female specimen also examined in the Museum Victoria was 80 centimeters (2.6 feet) long and weighed in at nearly three kilograms (8 pounds), or more than 10,000 times heavier than the tiny male. Norman, an octopus identification expert, knew he'd found something unusual because he didn't immediately recognize the species, said Tregenza. The male octopus, which approached them from the depths, weighed in at no more than a quarter of a gram (0.08 ounce) and was only 2.4 centimeters (0.9 inch) long. The researchers then waited in the eerie silence and used torches as light sources in the hope of attracting interesting passers-by, said Tregenza. Such expeditions involve taking a boat to sea on moonless nights and suspending a diver up to 20 meters (66 feet) into the pitch-black water. Norman of the Museum Victoria in Melbourne, Australia, and David Paul at the University of Melbourne photographed the animal while on a type of late-night diving expedition known as a blackwater hang.

The male blanket octopus recently photographed by researchers was shown to clutch tentacle segments in his suckers, said Tregenza. When they encounter potential predators, the octopuses waft the captured man-of-war tentacles in two pairs of its upper arms as an effective deterrent. The octopuses are immune to the tentacle's painful sting. Females have the odd appearance of a 'big pink drifting blanket' said Tregenza, explaining the origins of the octopus's name.Īmong their more unusual behavior, the octopuses employ a unique defense mechanism by tearing off the tentacles of passing Portuguese man-of-war jellyfish. They spend their entire life drifting in the open oceans of warm regions worldwide. So-called sexually dimorphic species are those, like humans, whose males and females are of different average sizes.īlanket octopuses are rarely seen.

'This is certainly the most dramatic example of sexual dimorphism in any large animal,' said Tregenza. But the recent observation marks the first time one has been spotted swimming about in its natural environment. Tregenza co-authored the study that reported the find in the latest issue of the New Zealand Journal of Marine and Freshwater Research.ĭead blanket octopus males ( Tremoctopus violaceus) have been collected before in plankton nets. 'Imagine a female the size of a person and the male a size of a walnut,' said Tom Tregenza, an evolutionary biologist at the University of Leeds in England. By contrast, females of the species grow up to two meters (6.6 feet) long. Divers spotted a male 2.4 centimeters (0.9 inches) long. This is reality for the male blanket octopus, which was recently spotted alive for the first time off Australia's northern coast.Īustralian and British marine biologists stumbled across the diminutive male octopus while scuba diving in the Great Barrier Reef. Imagine if your spouse was 40,000 times heavier and a hundred times larger than you.

Blanket octopus predators