of suckers! Cephalopods! Welcome to Jonathan Bird's Blue World! An octopus is on the prowl, looking for an
unsuspecting fish to pounce upon. A cuttlefish is hunting with mesmerizing colors
to distract its prey. A school of reef squid hover in the water
column. What do these magnificent animals have in
common? They are all cephalopods.
Cephalopod means head-foot because this
animals head (the part with the eyes) is connected to its feet. The part out in front that looks like a head
is actually the body. And in fact biologists dont call those
things feet, they are called arms. So cephalopod is actually a terrible name,
but its what we have got.
Squid, octopods, cuttlefish and nautiluses
are all members of the class cephalopoda, but the really weird thing is that cephalopods
are mollusks. So they are related to animals like snails
and clams, which seems a little crazy. This is based mostly on their internal construction,
not their outward appearance. Perhaps the most obvious difference between
most cephalopods and other mollusks is the apparent lack of a shell.
The octopuses do not have shells at all. The squid have a small internal shell. Nautiluses are the only cephalopods with an
external shell. Nautiluses are found in the South Pacific
and Indian oceans, typically in deep water.
Cephalopods have well-developed nervous systems,
much more sophisticated than other mollusks. And they can be quite inquisitive. The cephalopod eye is one of the most notable
examples of convergent evolution in all of the animal world, because this eye evolved
from completely different ancestors than the eyes of mammals, yet it turned out to function
in almost the exact same way. Cephalopods, therefore, have extremely good
eyesight.
Of course the most well-known of the cephalopods
are the octopuses, named for their eight arms. They are masters of disguise, able to change
colors and skin patterns instantly. With no shell, or bones the octopus can fit
through tiny holes. They make terrible pets because they can escape
from virtually any aquarium! The octopus has a mouth with a beak used to
bite prey.
A hunting octopus often balloons over a rock
to trap a fish. Then it will use venomous saliva to kill the
prey when it bites. But the Blue-Ringed octopus of the South Pacific
has venom so powerful that the bite of this octopus is lethal to a human. The mimic octopus is said to mimic other animals
in order to hunt or evade predators.
This one has a convincing flounder imitation
going on, but its unclear how looking like a flounder is advantageous. It might just be the most efficient way to
swim and stay camouflagedconvergent camouflage if you will. A coconut octopus in Indonesia carries a shell
so that when the need arises, she can hop inside and hide. This clever behavior makes the octopus a tool
user, putting her in a category of animals considered more sophisticated and intelligent,
like monkeys and dolphins.
In the cold water of Puget Sound, a Red Octopus
is carrying a crab home for dinner, walking on the tips of its arms. That takes coordination! Nearby, a Giant Pacific Octopus breathes by drawing
water into its mantle, a cavity in its body and squirting it back out through a siphon. Not only does this move water over the gills,
but it gives the octopus the ability to squirt water. The siphon can be used for jet propulsion,
squirting an octopus away at high speed.
A reef octopus in the Caribbean not only squirts
away from me, but leaves a smoke screen behind in the form of an ink cloud. Squid and cuttlefish are similar to octopuses,
but their small internal shell makes them rigid and torpedo-like. So, while the octopus often crawls along the
bottom, the squid and cuttlefish like to jet. In the North Atlantic Ocean, Longfin Squid
cruise through the New England shallows.
But when they get annoyed by my camerathey
can produce ink too. More than 8 thousand miles away from New England,
the waters of the Philippines are warm and clear. After the sun goes down, a Flamboyant cuttlefish
comes out to hunt. While the octopus has eight arms, the cuttlefish
and squid actually have ten.
Eight of them are of the same length, while
the other two are extra long, and used to grab prey. These two additional arms are called the tentacles. Cuttlefish are often quite curious, and sometimes
come right up to my camera for a look. Their skin patterns change rapidly thanks
to skin cells called chromatophores.
At the New England Aquarium in Boston, theres
an exhibit where you can watch cuttlefish up close. And when you look carefully, you can see the
chromatophores working. At feeding time, the cuttlefish pay close
attention, and they turn on the camouflage. Then the cuttlefish strikes.
Even slowed down to one quarter speed, its
lighting fast. With a high speed camera, a flamboyant cuttlefish
blah blah In another tank, a Giant Pacific Octopus guards
it eggs. All cephalopods lay eggs to reproduce. Octopuses tend to guard their eggs.
Back in Indonesia, the Coconut octopus is
releasing thousands of baby octopus hatchlings from her clutch of eggs. She carried them around for months while they
incubated. Squid and cuttlefish do no such thing. The Atlantic Longfin squid lays its eggs like
most squidcigar shaped bundles of eggs attached to the rocks or kelp and left to
fend for themselves! The Flamboyant Cuttlefish eggs are about the
size of a pea--laid on a rock.
Soon a baby cuttlefish is born. The cephalopods are an amazing group of animals. Its hard to imagine such advanced animals
being closely related to such primitive mollusks as the conch. Cephalopods can change color and texture with
chromatophores, they have extremely sharp eyesight, multiple arms that are capable of
complex tasks, and they are clever enough to use tools! They are definitely one of my favorite inhabitants
of the Blue World..
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