It's hard to make a good cartoon cephalopod, I guess. Yesterday I was disappointed about the Squidbillies. Tomorrow I may despair of Spongebob's pal Squidward. Today, I sigh over Nemo's little octopus friend Pearl.

I was profoundly impressed with the combination of scientific accuracy and aesthetic appeal achieved by the writer and animators of Finding Nemo. I mean, that song Mr. Ray sings about naming the zones of the ocean? Total brilliance!

And the attention to anatomical detail! Okay, Peach's suction cups aren't in nice ambulacral grooves, but at least her mouth's in the right place:



(Thought she shouldn't have eyes right above her mouth. Sea star photoreceptors are actually all the way out on the tips of each arm. Yup, they have five light/dark sensitive patches! But you know, I'm willing to forgive Peach her eyes, because her mouth's in the right place.)

Pearl the octopus' mouth is in the wrong place. Cartoonists always seem to have a problem putting cephalopod mouths in the middle of their arms:



Sigh.

But Pearl has a bigger problem than a misplaced mouth. Every other kid in Mr. Ray's class is a species that could plausibly be found on a tropical coral reef. Except for her. She's a midwater octopus, the kind that lives way out to sea over deep water. How do I know? The dead giveaway is those little "ears." They're actually fins, like a squid's fins.

Octopuses come in two flavors: Cirrata and Incirrata. Just like the two flavors of squid, they're named for a rather obscure anatomical difference: the presence or absence of little flaps of skin called cirri.

The cirri are the long, slender, muscular papillae lining the arm. The
exact function of the cirri is unknown but they are thought to play a
role in feeding.

More distinctive than the cirri, however, are the fins--present in cirrate octopods and absent in incirrates. Even more distinctive is the difference in their preferred habitats--again, just like myopsid and oegopsid squids. Cirrates are all your common nearshore, benthic octopuses, the ones you'd expect to see crawling around a tidepool, mud flat, or reef. Incirrates are all deep-sea, midwater, looking almost like jellyfish when they swim, never settling down to the bottom.

As a cirrate octopus, Pearl follows this behavior, and stays up off the seafloor. So, yay consistency! But she's still in the wrong place. Talk about a commute, from the deep-sea to a shallow coral reef! Can she take the bus? Is the reef is a charter school?

Did the writers and animators even think through these implications, or did they just happen to see a picture of a dumbo octopus, and make an impulse decision?



Post-Script. Thanks to the rugbyologist for the discussion that prompted today's article!

Post-Post-Script. I keep putting oddball stuff like this in the Science&Society category, but if anyone thinks it ought to go anywhere else, do alert me.