The Blanket Octopus

Blanket octopus 

It may look like a sheet of silk going flowing through the water, but this stunning creature is a Blanket Octopus (family Tremoctopodidae).  These pelagic cephalopods drift along the surface and mid waters (120-750 m) along the Mediterranean and the North and South Atlantic Ocean.

Unlike most cephalopods, which shoot ink as a defence, the blanket octopus uses its net like “blanket” make it self look for daunting in the hopes of scaring off predators. This blanket, for which it was named, is usually stored within its mantle but when threatened, the octopus can fold out the two larger arms on which the blanket is attached. The other arms do not have this webbing and are much shorter.  

Portuguese man o' war

Don’t mistake this creature for a defenceless dainty beauty however. They are immune to Portuguese man o' war stings, which pack a nasty punch even after death. The octopus breaks off bits of tentacle and uses them for defence. While this behaviour isn’t unique to this animal, several species of marine gastropods have been known to utilize cnidarian nematocysts for defence, there are still only a handful of creatures able to withstand a Portuguese man o' war famously powerful venom.

In addition to being known for its shimmery appendages, these unique creates is also famous for its extreme sexual dimorphism. The females can grow as large as 2m in length while mature males only grow to a few centimetres. That means that a fully mature male is 1:10,000 the size of a fully mature female! Up until 2001, only females had ever been seen alive. However, during a series of night dives, Dr Richard Norman was able to catch a glimpse of a fully mature male on camera.

Male blanket octopus

Sexual dimorphism is commonly found among animals where one sex has discovered a particular survival or mating technique. The blanket octopus is just one of four pelagic cephalopod groups which also show great sexual size differences (the others being “paper nautiluses”, the football octopus, and a deeper water octopus Haliphron atlanticus) but blanket octopus is by far the most extreme case.

It also means that only the ladies get the large and lovely gowns. Good going girls!