Right-Arm Innovation

13 May 2014 Comments Off on Right-Arm Innovation


All right, first things first: I have two announcements to make, one in shameless promotion of myself, and another in shameless promotion of my graduate institute. UNAM, you see, is hosting a showcase event on the 26th of this month, and among the planned activities is a nanoimaging competition—there’s no theme in particular, so you can submit images of anything that’s nanoscale, and since “nanoscale” is frequently stretched to mean anywhere from a few Planck lengths to a few centimeters, you can get pretty much anything you want into this contest. I’ll be competing as well (look for the grotesquely misshapen insect head—that’s a good way to find my entry), so feel free to visit the event and bask in the sheer glory of my scientific ineptitude—the winners will be decided by public vote, by the way, and while I’m not saying that you should all vote for me (although you should), I fully expect the support of any grotesquely misshapen insect head aficionados that might be among you.

The second announcement is that UNAM is accepting graduate students, and since UNAM is a cluster of over ten laboratories stacked on top of each other, there’s a lot of good research going on in there. You also have free access to top-notch equipment from wildly different fields, which you can use, for example, to put grotesquely misshapen insect heads in an electron microscope and let it rip (do not try this at home, or anywhere else for that matter—also, in the event that our SEM should break down this week, I’d like to note that I am completely uninvolved, and that I will not be taking my contest images until after this column is published). So if you’re interested in learning what this newfangled “nanoscience” contraption is all about, give UNAM’s Nanoday event a spin, and while you’re at it, you should come over to my poster and say “hello” as well.

In any case, I now notice that I’ve spent one-third of the column being overly verbose about something I could have said in two sentences (“There’s a contest on the 26th, vote for me; UNAM is accepting graduate students, apply and become a graduate student), so I’ll now get to the main course for this week—cephalopods.

Octopuses are probably the most familiar of these tentacled, brainy mollusks, and they are split neatly into two subgroups. Cirrate octopuses are deep-sea animals with conspicuous swimming fins, an internal shell and feathery strands that flank their suckers (if you’ve seen a dumbo octopus, that’s a cirrate), while incirrate octopuses are the classic variant, lacking cirrate features but featuring an ink sac in compensation. Notable among their number is the paper nautilus, Argonauta, which earns its name from the paper-thin shell that the females secrete to hide their eggs in—the mother also coils neatly within this cradle, which makes her look greatly like a nautilus in a flimsy shell. Another notable species is the blanket octopus, Tremoctopus, famed not only for the massive size difference between the sexes (the female can reach about two meters in length, while the male is barely a few centimeters), but also for the ability to seize the incredibly venomous tentacles of the Portuguese man-of-war and brandish them as a defensive weapon. This species receives its name from the membranous curtains that stretch between the arms of the female, which make her look too large to be an easy meal for most predators. The mimic octopus is a third curious octopus, and is something of an Internet celebrity, its ability to imitate just about every animal under the waves having earned it a healthy measure of respect from the World Wide Web.

Octopuses are notable for their eight arms, but they are not the only cephalopods to possess this trait: the vampire squid, despite its name, shares more with octopuses than with squid or cuttlefish, possessing eight arms and two feeble, filamentous organs instead of the full set of ten limbs that characterizes the latter two groups (unsurprisingly, the filaments of the vampire squid do not correspond to the tentacles of true squid—the former are modified from the second set of arms, the latter from the fourth). Also, despite its rather intimidating name, this vampire is in fact quite a placid animal—the thin filaments allow it to feed without expending much in the way of energy, as their sticky surface passively gathers marine snow from the abyssal depths that the animal inhabits (active hunting is too energy-intensive for this lightless, oxygen-poor environment, and such a feeding regimen allows the lazy cephalopod to exploit the constant rain of organic detritus from the shallower parts of the ocean). Octopus squid (and here we go again with “The Last Airbender” chimeras) also possess eight arms, but are squid proper—their tentacles, while present during embryonic development, do not grow with the animal and remain as tiny stubs that eventually disappear as the squid matures.

On the squid side of things, there are abyssal anglers that dangle their sticky, flypaper-like tentacle tips just above the ocean floor to capture bottom-dwelling crustaceans; siphonophore mimics that swim perfectly perpendicularly to the water column and use flaps on their tails to look like colonies of dangerous, stinging hydrozoans; would-be aviators that flatten their arms and fins to glide through the skies; and deep-sea horrors that constantly watch for prey with one gigantic eye turned to the sky—but that’s a topic for another column.