This bizarre structure is not from the prop shop of a science fiction movie, though it may well provide inspiration there.
What might you guess this claw-like appendage is attached to? Would you have guessed . . . a mite? As in, the same group of spider-relative arachnids that brought us the dust mite, the spider mite (bane of gardeners), and the gall mite, which makes modern art in leaf form? OK, maybe you would guess that, because mites have also brought us the chigger; the scabies and mange mites; Varroa destructor, the parasitic mite that has wreaked havoc among honeybees; and, of course, everyone's favorite: Demodex mites, the critters that frolic, eat, poop, and make little mites in your eyelashes, hair follicles, and sebaceous glands. And did I mention mites' cousins are ticks?
But still, you wouldn't expect such an intricate, sci-fi cool appendage on THIS particular mite, because the owner of this claw is a soil mite. But there's something different about this mite other than its homely digs. Because here's the thing. Your conventional mite looks like this:
And the owner of that wicked claw looks like this:
That's their face, by the way, on the right. And these aren't even adults. They're two different nymph stages.
The full-size adults look like this:
Fully extended adult mites are around 600 micrometers long, about 12 times their width. And this is not even the limit for mites of this type. Another species in this group can get as long and wormy as this. On the other hand, consider that, at a few hundred micrometers long, this complex multicellular arthropod is roughly the same size as some large single-celled microbes like amoebae.
This mite is a new species -- Osperalycus tenerphagus -- described and named last month by scientists at Ohio State University and the USDA Agricultural Research Service. Many mysteries remain about this mite; among them, what it eats. One thing that is not a mystery are the mites' origins. They were fished out of the soil from a university campus and a chestnut plantation. Yet from boring ol' dirt came a worm-like mite of some extraordinarily beautiful details, and not just that claw.
This montage, below, depicts the surface texture of these mites under the scanning electron microscope. On the upper left, the cuticle is extended, revealing a beautiful lacy honeycomb pattern on the cuticle between rows of ridges bearing paddles (rather colorfully called palettes by biologists). On the right, the cuticle is contracted. The bottom two images are an oblique view, expanded on the let and contracted on the right. You can see why they call them palettes.
Here's a closeup of the extended cuticle.
And here it is contracted.
What might be the reason for this fabulous upholstery? Scientists suspect that the paddles are where the mite meets the road, so to speak. Despite the fact that the paddles seem to point the wrong way for movement via peristalsis, like an earthworm or your esophagus when you swallow (the palettes' broad sides align with the axis of the worm, and besides, these mites don't move by peristalsis anyway), the mite is still somehow using them like oars, they say. The cuticle can expand and contract in a non-peristaltic way via both the hydraulic pressure of their bodies, and by a layer of muscle just under their skin. Using this accordion-like system, these mites manage to row their way through the tiny spaces between particles in soil, plying the vast and mysterious Sea of Dirt.
Bolton S.J., Klompen H., Bauchan G.R. & Ochoa R. (2014). A new genus and species of Nematalycidae (Acari: Endeostigmata), Journal of Natural History, 1-15. DOI: 10.1080/00222933.2013.859318