This article was published in Scientific American’s former blog network and reflects the views of the author, not necessarily those of Scientific American
Nerds have a particular fascination for the Cthulhu mythos of horror novelist and all-around-weird-guy H. P. Lovecraft. In Lovecraft's stories, Cthulhu was a tentacle-faced titanic god-monster who slept in a mythic undersea lair called R'lyheh, dreaming of the day he could emerge to destroy humanity. Nerds hold the mythic being in high esteem and have created a variety of Cthulhu-themed products, including plush Cthluhus, Cthulhu car accessories, Cthulhu bumper stickers ("Cthulhu 'NN: Why Choose the Lesser Evil?), Hello Cthulhu logos (Remember Hello Kittty?), and of course, My Little Cthulhu.
Now the titanic horror has his own microbial namesake with a tongue-twisting name worthy of Lovecraft: the adorably cute Cthulhu macrofasciculumque.
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And where is this Cthulhu to be found? Not in a place of horror in the most remote reaches of the south Pacific Ocean. Oh no. This Cthulhu is found in the digestive system of the considerably less-exotic Cuban subterranean termite. It turns out termite guts are a surprisingly popular place for protists to hang out, as a vast array of huge , shaggy microbes (see these images of Trichonympha, Spirotrichonympha, Dinenympha, and Pyrsonympha, for instance) hold court there. Who would have guessed that termite backsides would contain such a menagerie of interesting beasties? But it is so.
The authors of a study published in PLoS ONE early last year decided to investigate some of the smaller members of this coterie, since most of the larger one have already been described. So, while examining the "hindgut community" of a Cuban subterranean termite (we won't think about what was done to the termite to retrieve the sample), they saw a new mid-sized protist of a body type they hadn't observed before.
As you can see in the photo at the top of this post, this new microbe resembles a teardrop having a bad hair day. The "hairs" are actually flagella, the same structure used by sperm cells to swim, but in this case instead of a single flagellum there is a bundle of about 20. Here's a closeup of the attachment of the bundles to the cell. The tentacular Cthulhu resemblance is unmistakable here, although it also looks a bit like a blue whale opening its mouth to reveal its massive baleen.
The flagellar bundle of Cthulhu. Scale bar 2 micrometers. Fig 2B from James et al. 2013. Click image for source.
These flagella propel the cell forward by paddling. The flagella unite on the forward stroke, and then on the backward power stroke they splay out, presumably to maximize surface area and thrust the way a fin increases the surface area of a diver's feet or hands.
Here's a video of what this looks like:
There may also be an extra singular flagellum attached on or near the rear "axostyle", the pointy-outy thing on the back of the protist.
And Cthulhu, in turn, has its own adorable counterpart, Cthylla microfasciculumque, named for a supposed secret daughter of Cthulhu. Cthylla appears to function in the same way except it is smaller (about 10-15 micrometers long, as opposed to about 20 for Cthulhu), has fewer flagella in the bundle on its front side (five), and definitely possesses a single flagellum on or near its axostyle. The scientists discovered this similar protist in the gut of a different termite species, the eastern subterranean termite.
Studying smaller, simpler termite protists like these is important, the authors say, for understanding the evolution of the big fancy ones. These all appear to have descended from a single common ancestor and form the "parabasalids", a group of flagellated protists closely associated with animals which includes at least one sexually-transmitted human parasite.
Big, complex parabasalids appear to have evolved multiple times from the little ones. There are multiple variations on the theme of bigness, as some of the big ones have many DNA storage compartments called nuclei and some only one, and some have duplicated all or part of the complex internal skeleton of these protists called the "karyomastigont", while some have not (presumably, there's a whoooole lot of cytosol inside those). Understanding the relationships between big parabasalids and little parabasalids can help the scientists understand how the big ones evolved from the small ones, and see whether they can detect any illuminating evolutionary patterns or themes in these little organisms hidden inside some of the most important nutrient recyclers on Earth.
It should, however, be noted that there is one very important difference between Cthulu and its namesake besides their size. Instead of devouring fleeing, insane humans, this protist feeds on a gentle stream of lignin and cellulose, the stone-cold-sober structural components of wood sent their way by the termite's tireless efforts. That's right: this Cthulhu is vegetarian.
Reference
James E.R., Okamoto N., Burki F., Scheffrahn R.H., Keeling P.J. & Badger J.H. (2013). Cthulhu Macrofasciculumque n. g., n. sp. and Cthylla Microfasciculumque n. g., n. sp., a Newly Identified Lineage of Parabasalian Termite Symbionts, PLoS ONE, 8 (3) e58509. DOI: 10.1371/journal.pone.0058509.s003