Violet blanket octopus
The common blanket octopus or violet blanket octopus (Tremoctopus violaceus ) is a large octopus of the family Tremoctopodidae found worldwide in the epipelagic zone of warm seas. The degree of sexual dimorphism in this species is very high, with females growing up to two meters in length, whereas males grow to about 2.4 cm. The first live specimen of a male was not seen until 2002 off the Great Barrier Reef. Individual weights of males and females differ by a factor of about 10,000 and potentially more.
Males and small females of less than 7 cm have been reported to carry with them the tentacles of the Portuguese man o' war. It is speculated that these tentacles serve both as a defensive mechanism and possibly as a method of capturing prey. This mechanism is no longer useful at larger sizes, which may be why males of this species are so small. The web between the arms of the mature female octopus serves as a defensive measure as well, making the animal appear larger, and being easily detached if bitten into by a predator. The complete mitogenome of T. violaceus is a circular double-stranded DNA sequence that is 16,015 base-pairs long.
The third right arm in male blanket octopus is called the hectocotylus, which has a sperm-filled pouch between the arms. When the male is ready to mate, the pouch ruptures, and sperm is released into the arm. He then cuts this arm off and gives it to a female. It is likely that the male dies after mating. The female stores the arm in her mantle to be used when she is ready to fertilize her eggs. She may store several hectocotyluses from different males at once.
