The infinite, infinitesimal world of air

When June rolls around in New England, the air becomes thick with pollen. Tiny yellow grains powder every surface and collect in lakes and ponds to form questionable, sulfur-like deposits. Thousands of people develop allergies. Really, it’s impossible not to notice that the air has suddenly been filled with foreign particles. But what’s a bit harder to see is that the air is always filled with tiny bits of stuff, constantly swirling and drifting, held aloft by the chaotic motion of the wind. We don’t normally see them, but there are ways to take a closer look.

Recently, I’ve been  reading Air by William Bryant Logan and was amazed to learn that every cubic yard of air contains tens of thousands, maybe even hundreds of thousands of fungal spores. My favorite chapter by far was “The Spore Sucker,” in which the author meets a mycologist with a device that catches small particles from the air. It’s built with a vacuum pump and a cylindrical cassette that holds a piece of double sided tape. After the mycologist pumps air through the device for fifteen minutes, he mounts the tape on a glass slide and looks at it under a microscope. He identifies several species of fungi by their spores, as well as a bunch of other interesting objects. Neat! I wanted to try it, too.

Well, I didn’t have any kind of fancy vacuum pump, nor a cassette like the one described in the book. I couldn’t even find any double-sided tape. But I made do with a vacuum cleaner, a paper towel tube, and some packing tape. What I ended up with was a single-use poor imitation of the original spore sucker, but it was good enough for me. After running the vacuum cleaner outside for fifteen minutes, I dusted off my digital microscope and took a look at what I’d found.

The following photos were taken with a Celestron LCD Digital Microscope. They’re not true color because I left a green filter on the light source. Oops. If you must know, most of this stuff is actually just brown.

The dark, petal-like object on the left side of this snapshot is a wing scale of a moth. Almost all members of the order Lepidoptera (from the Greek lepido-, meaning scale, and pteron, wing) have hundreds of thousands of scales like this arranged like shingles on each of their four wings. They produce the exquisite colors and patterns on the wings, either through pigments or through structural coloration.

Anyone who’s touched a butterfly knows how easy it is to accidentally brush the scales off of a wing. As a result, the air is full of microscopic scales, shed from these flying insects. Mostly moths, because their wing scales tend to be looser. Who knows how many you’ve inhaled in your lifetime? Enough to rebuild a whole new moth? I try not to think about this stuff too often.

These hydra-like hairs were by far the largest objects on the slide, even larger than a pollen grain (the round thing in the bottom left). You might have noticed that I had to zoom out to fit the whole hair in the frame. There were several of these on the slide, and at first, I thought they were fibers from the cardboard tube I used to hold the tape. However, these objects are actually plant hairs, such as those that would grow on the underside of a leaf. This particular branched hair has “arms” that are less than a millimeter long—you wouldn’t even notice them on the leaf surface if you didn’t look carefully.

ascus-fungal-spores

I did a double-take when I saw this on my microscope screen.

Look at this. It looks like a pea-pod.

Isn’t it cute?

What you’re looking at is a photograph of an ascus, the characteristic sexual structure of the ascomycetes. Asci grow in the fruiting bodies of many fungi in the phylum Ascomycota, and they serve to hold and disperse the eight ascospores contained inside like peas in a pod. Many have a mechanism to eject spores forcefully using hydraulic pressure. However, once all eight spores have been ejected, the ascus usually withers and is no longer useful. It’s definitely supposed to remain attached to the fruiting body. So what was this one doing floating around in the air? And why does it only contain six spores?

It certainly looks like you could fit exactly two more spores in the empty space in this pod structure. Evidently, this ascus had ejected two spores when it somehow detached from its fungus and joined the countless spores already drifting through the air.

pollen-grains

Of course, how could we talk about organic material in the air without mentioning pollen? You can’t miss it this time of year. These look about the right size to be pollen grains, but it’s not easy to identify specific species. The grain on the left looks like it has two lobes attached to a main body, which suggests that it might be a grain of pollen from a pine tree. These pollen grains are shaped a bit like water molecules, with two wings to help with wind dispersal. In this case, it makes sense that I found this grain in the air, since it’s built specifically to float around for a long time.

I still don’t know what’s up with the grains in the right-hand picture. I came across a lot of them with this kind of triangular structure, and there are definitely many types of pollen with three-fold symmetry, such as maple and oak. Perhaps these belong to one of those species (there are quite a few maple trees in my area, after all). If you’ve got any idea what they are, please let me know! This has been bothering me way more than it should.

If we think about it, we all know in theory that the air around us contains something other than pure, filtered nitrogen and oxygen. But because we’re always looking through the air as if it were empty space, these solid bits and pieces tend to slip our minds. There’s something quite exhilarating about catching a few of these floating particles and taking a look for yourself. Next time you’ve got some tape, a microscope, and an hour to spare, I encourage you to give it a try.

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