Occasional and skippable one-paragraph commercial announcement: the microscopy material appearing in this blog at the moment comes from out-takes from an upcoming book. Once you have read this, you will see why we decided to leave this bit out of Australian Backyard Naturalist (which by the way, you don't need to buy or read to follow any of this).
Even under x20 with a dissecting microscope, tardigrades are small wriggly blobs, just visible enough to pick up with a brush or a needle, to transfer onto a well slide.
Under a high-power microscope, you will be able to see that they have eight legs, each one usually ending in a claw: only the soil tardigrades are clawless.
Sometimes, the two hindmost legs may be curled up under the body, but after you have seen a few tardigrades, you will learn to recognise the curved claws on the legs. The individual shown here has its two hind legs almost hidden.
Note inserted October 2014: that post has finally been written, and is online.
Then you turn the sieve over and run some water the other way, to wash the tardigrades and anything about their size off the sieve and into a small amount of water. The best way to do this is with a wash bottle.
After that, you just need to search carefully through the remnants in a shallow dish, to see what you can spot moving around. Expect to find all sorts of surprises in there, along with the tardigrades, including large protozoa, nematodes and small mites at the very least. Leave the dish completely still and look for any movement in and under the bits of litter and sand grains. At first, you probably won't see the tiny wriggling shapes without a microscope, but once you know what to look for, a good hand lens will reveal the larger tardigrades.
Another way of catching them
A 'Dust Buster' or other portable vacuum cleaner can save you a lot of work. Fit one with a clean bag and use it to sample tree trunks, lichens and moss mats near waterfalls. You can use it to pick up mites, springtails, beetles, flies, bark lice (book lice) and small spiders. Ian Kinchin, who invented this method, said it was particularly useful on tardigrades.
You need to have a white dish or ice cream container, large enough to let you shake the vacuum cleaner bag into it, banging it with your hand to shake off any small passengers that are hanging on. Then tip the contents of the dish into a holding jar.
In my attempts so far, I think I have used moss that was too dry, so I only got small numbers of mites from the moss. One day, I plan to try two things: first, I want to choose a moss mat and clean it of all twigs, and then 'vacuum' it after rain; second, I want to try watering a moss mat with bottles of water, waiting a few minutes and then 'vacuuming' it. One day, maybe, but you can always beat me to it: if you do, please post a comment here.
And the moss mat flushing method
Seen at close range, a moss mat offers lots of handy hiding places for small life forms.
In a very real sense (as you will see, once you think about scales), the moss mat is a sort of uniform jungle, though the shot on the right also shows a couple of capsules, the devices from which mosses release spores that can blow around and carry the moss genes to a new place.
To catch them, you need a good light source, a Petri dish or a saucer, some moss and some water and/or 70% alcohol. I prefer using just water, so the animals live and I can release them later. The alcohol would kill them.
If you slowly add water to a moss mat in a bowl, some of the animals will climb up into the dry. Adding 70% alcohol with an eye dropper has the same effect, but you need to watch out for fire, and avoid breathing the fumes.* Do this in a flat white dish in the open, pick up the animals with an eye-dropper, and put them in a large amount of fresh sea water to reduce the risk to them—and you!
Remember that tweezers are bad news for animals. You should use a paint brush to pick up any animals you want to mount on a slide for closer examination, and always use well slides to avoid crushing the animals.
References(started April 2015)
My thanks to Thomas Boothby (see comments below) who drew my attention to ISTH, the International Society of Tardigrade Hunters. This is an excellent place to go, and you will get real experts there, as opposed to this fumbling enthusiast.
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This blog covers quite a few different things, so I tag each post. I also blog about history, and I am currently writing a series of books called Not your usual... and the first two have been accepted by Five Mile Press, The offcuts appear here with the tag Not Your Usual... . For a taste of Australian tall tales, try the tags Speewah or Crooked Mick. For a miscellany of oddities, try the tag temporary obsessions. And language is covered under the tags Descants and Curiosities, while stuff about small life is under Wee beasties.