male half of one of the strangest marine couples
has been seen alive for the first time. The
blanket octopus shows the greatest size difference
between sexes of any large animal, with the
male 100 times smaller and 40,000 times lighter
than the female.
Tom Tregenza saw the creature whilst diving
off the Great Barrier Reef with colleagues
from Melbourne and Tasmania. The blanket
octopus spends its entire life cycle in the
open ocean, so its rarely encountered,
he said. Dead males have been found
in nets, but this is the first time a live
one has been seen. Although mature, it is
just 2.4cm long and weighs just 0.25g. In
contrast, mature females can grow up to 2m
long, and weigh around 10kg.
blanket octopuses develop an extra arm within
a spherical pouch, used for reproduction.
When they locate a female and mate, the arm
is severed and passed to the female, remaining
in the females mantle cavity until used
to fertilise her eggs. After mating, the male
is believed to die.
dont really know why the octopus has
developed with this huge difference in size,
said Dr Tregenza (right). One
theory is that the male gains an advantage
by remaining small, as it reduces the time
taken to reach sexual maturity. We know that
males are in competition with each other over
females, as females are often found with several
arms within their mantle cavity.