Sunday, 25 January 2015

Bobtail Squid

Image: Chris Frazee and Margaret McFall-Ngai
The Dumbo Octopus has been strutting around like he owns the place for far too long. It's time for a challenger to rise up and get those dainty tentacles on the Cutest Cephalopod tiara.

It can only be the Bobtail Squid, some 60 species in the Sepiolidae family. Despite their name, they're not really squid. They look and live more like cuttlefish, and they are indeed more closely related to them. But they're not really cuttlefish, either.

Instead, they're... Bobtail Squid. They're just different is all. Deal with it.

Image: Patrick Randall
Bobtails are called Bobtails because they lack the long, streamlined mantle seen in many squid. They're rather curtailed in comparison, with a short, squat body that is only about 1 to 8 cm (half inch to 3 inches) long.

You can see why they're also known as Dumpling Squid!

There are several differences between dumplings and Dumpling Squid. Yes, several. One is that while a dumpling may be filled with fish or tiny lumps of a cow, the dumpling itself didn't put them there like some horror movie where empty parcels of dough come alive and reduce their victims to a skeleton in a matter of minutes like a pack of piranha. Leave that to the slugs. Although, if you could train them to do that it'd save the chef some time.

Image: Ewald Rübsamen
Austrorossia mastigophora
Bobtail Squid are certainly carnivorous, just like every other cephalopod. They have enormous eyes and, like cuttlefish, bear eight short arms and two long, retractable tentacles for catching small fish, shrimp and the like.

They can also swim around if they want, though most Bobtails spend a lot of their time on the seabed. When they do swim, they do so by flapping an enormous pair of fins much like a Dumbo Octopus. This is unlike cuttlefish who can simply undulate their fins to get around or hover motionless in elegant fashion.

This difference in swimming style probably has something to do with the Bobtail's lack of what's known as a cuttlebone. The cuttlebone is a tough, internal structure which is all that's left of the cuttlefish's ancestral shell. It's full of gas and the cuttlefish uses it to control buoyancy. Without this bit of technological fine-tuning, the Bobtail is left flapping around like an adorable maniac.

All this activity occurs at night, by day the little Bobtails hide away from predators. But there's a clear problem...

Image: Mark Norman / Museum Victoria
Euprymna tasmanica
Just look at them! Many Bobtail Squid shine and sparkle like jewels! They're difficult to ignore. And they also seem to lack the expert colour changing abilities seen in so many octopods and cuttlefish, so camouflage isn't a great option either.

It's time to ninja things up.

Video: liquidguru

Bobtail Squid bury themselves beneath the surface of the seabed. They rock back and forth to shift the sand and mud out of the way. Once they're buried up to the eyeballs they use their tentacles to spread sediment over their back, entirely covering their glistening and decidedly eye-catching body. They're also covered in glands that secrete a sticky mucus so they can glue sand onto their body!

You have to be thorough when you're THAT glamorous. Glamorous and covered in mucus. It does NOT get any better!

Image: Rickard Zerpe
Sticky suit of sand
At night, when they're out on the prowl, they have another problem. Instead of hiding their shiny selves in drab sand, they need to hide the shadow they cast in moon and starlit nights.

This time they must say hello to a little friend. By which I mean they need to house and feed millions of microscopic bacteria. Pff. Same old story. You say "hi, how are you?" to a chum and the next thing you know they're sleeping on the couch, eating all your food and inviting all their friends over for a party.

The bacteria in question is Vibrio fischeri. It can live just fine in the water but it prefers to have somewhere nice to stay where it doesn't have to get its own food. Bobtail Squid provide them with just such a place. It's a special organ in their mantle, full of delicious sugars and amino acids. Mmmmm... amino acid.
Image: Rickard Zerpe
Nibbling on an enormous shrimp
The bacteria move in, flourish and reproduce. Pretty soon they reach a certain density and begin to glow. The Bobtail Squid is now in possession of a bioluminescent light organ. It can control precisely how much light escapes by opening and closing a kind of iris. Now our plucky Bobtail can hunt with confidence as an eerie glow masks their shadow from prying, predatory eyes.

At least some Bobtail Squid will rudely eject some 90% of their bacteria every morning, simply squirting them out through some pores in their light organ. The bacteria that are left will have plenty to eat and divide and divide and divide all day so they glow anew come nightfall.

This form of camouflage is known as countershading. Most Bobtail Squid live in shallow water and do it at night to merge into the moonlight, but there are many creatures who do the same thing to mask their shadow in the twilight haze of the deep sea.

Well, whaddaya know...

Video: EVNautilus

Deep sea Bobtail Squid!

There are deep sea Bobtail Squid who spend a lot of their time resting on the sea floor, just like their shallow water brethren...

Video: NOAA Okeanos Explorer Program

But others are far more pelagic, enjoying the open ocean and not visiting the seabed much at all.

Image: Richard E. Young
Heteroteuthis hawaiiensis
A lot of these deep sea Bobtails are known only from a few specimens but one, Heteroteuthis hawaiiensis, is much better studied. It's been seen across the Atlantic, from the Caribbean to the Mediterranean, down to depths of 1,600 metres (5,250 feet).

One really cool thing about them is they've added a whole new ninja defence to their arsenal. Remember how Bobtails can eject 90% of their glow-in-the-dark bacteria every morning? Well, H. hawaiiensis does something similar. They dazzle predators by squirting a cloud of bioluminescence at them and escape in a puff of light!

A Bobtail's relationship with glowing bacteria begins at an exceedingly early age.

Image: Adrien Uichico
Sexy times
Like other cephalopods, the male uses a specially modified arm to pass a spermatophore over to the female.

She then lays a clutch of eggs. The eggs are sticky and can be covered in sand to hide them from predators.

Image: Macroscopic Solutions
Hawaiian Bobtail Squid (Euprymna scolopes) paralarva
The eggs hatch into into little babies known as paralarvae. They look a lot like the adults, so they're not proper larvae, but they're still not miniature versions of their parents. At least they already have their light organ so glowing bacteria will immediately start moving in.

The youngsters grow quickly. In some species they could be laying eggs of their own in a couple months and dead at just 3 months old. You can bury yourself underground, stick camouflage onto your body with glue or infest your body with bacteria to act as a cloaking device, but you can't stop the months from rolling by.

Live fast, die pretty.


TexWisGirl said...

adorable is right!

Lear's Fool said...

I can seriously watch those little guys burying themselves in the sand for an hour.

Porakiya Draekojin said...


stregajewellry said...

I like any kind of squid or octopus but this little guy has to be one of my all time favorites! When he is covering himself in sand.....amazing!

Crunchy said...


Joseph Jameson-Gould said...

@TexWisGirl: Yes!

@Lear's Fool: The tentacle action is ridiculous!

@Porakiya Draekojin: Haha! So true!

@stregajewellry: All time favourites, woo!

@Crunchy: Yup!

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