Although it is the home
of approximately 98% of the ocean’s species, the deep sea is a frontier yet to
be explored by natural scientists. Of the estimated 500.000 to 10 million
species living on or above the seafloor, new species are discovered and
described by marine biologists every year. Being one of the biggest and most
extreme environments on Earth, the deep sea’s biodiversity is enormous in both
species of prey and predators. From demonic red octopi to gigantic squid
wrestling with sperm whales, the most interesting group of marine predators
would be the deep sea’s cephalopods.
The biggest problem
living as a squid at 5000 meters depth is the pitch black environment you have
to hunt in. A great variety of cephalopods have adapted to their surroundings
in the most extreme ways. One of the easiest feeding strategies is what we call
“passive hunting”, and one of the more scary-looking squid known to science –
the genus Magnapinna – uses this
technique in the most bizarre way. Known commonly as Bigfin squid, or
Long-armed squid, this group is known for its irregular big fin-size and
extremely long arms. Although previously only known from caught juveniles, in
2007 an eerie video was made by a research facility in the Gulf of Mexico. What
they saw was a 8 meters-long adult squid, floating around in the abyss.
Another more obvious
feeding strategy is active hunting: squid are known to chase and ambush their
prey using their intelligence and extremely complicated eyes. While we know
that the eyes of squid are highly adapted and look similar to those of a
mammal, there’s one species that takes it a step further. The so-called
strawberry squid (Histioteuthis
heteropsis) gets its name from the strawberry-like appearance of its skin.
The light-producing speckles, or photophores, are supposed to confuse
predators. What’s more interesting however, is the fact that it has one
“normal” eye and one big green eye. It is believed that the smaller eye detects
bioluminescence generated from potential prey, while the other eye watches the
sky and filters faint light from above.
While the strawberry
squid tries to confuse its own predators, sometimes the best defense is simply
being bigger than the predator. Some squid have evolved to be gigantic, take
for example the Humboldt squid (Dosidicus
gigas) from the gulf of Mexico. The human sized squid are known to be
hostile towards divers and even hunt in packs – sometimes referred to as “a
squad of squid”. An even bigger squid can be found in the deep: the Giant and
Colossal squid (genus Architeuthis
and Mesonychoteuthis) are known to
reach sizes over 10 meters. There is only one animal capable of fighting a
gigantic squid: the 16-meter long Sperm whale. Although never observed by
biologists, evidence of squid-whale battles can be found on stranded whales.
Circular marks, believed to be caused by the suckers of the squid, cover the hide
of several found Sperm whales.
Lastly, there’s one
group of cephalopods often overlooked by the general public. Having the
creepiest name from the deep sea, the Vampire squid is one of the most
interesting organisms on Earth. Its Latin name Vampyroteuthis infernalis literally means “vampiric squid from
hell”, but its name is scarier than the animal itself. The Vampire squid feeds
on the so-called deep sea snow: flakes of waste material that slowly falls to
the ocean floor. It uses a long thread-like appendage to collect the snow and
brings it to its mouth.
Thought to be the common
ancestor of both squid and octopi, the bright red molluscs share a lot of
characters with the other cephalopods. There are however some differences. When
threatened, Vampire squids cannot simply swim away. Instead, they use an unique
arsenal of defensive strategies. The filaments between their tentacles can be
used to protect their soft bodies, exposing spiny structures on the inside of
the tentacles. In addition, Vampire squid have no ink-sacs like other lineages,
but can emit fluorescent fluids to scare predators away.
There’s a lot we still
don’t know about the deep sea and its inhabitants, but every day new species
are being discovered by marine biologists. We don’t have to look for other
planets to find aliens, the weirdest organisms can be found below the waves,
waiting for us.
Hi I’m Werner, master student and invertebrate
enthusiast. Most information was found through the Monterey Bay Aquarium
Research Institute: if you’re interested in deep sea stuff like me, check out