While I’ve been spending the past few days rinsing dishes, measuring soil pH, and rinsing more dishes, my lab mates have been glued to the microscopes, counting nematodes, rotifers, and tardigrades (oh my!). As I mentioned in my previous post, the Soils Team of the Dry Valleys LTER is interested in the invertebrate diversity and productivity in varying soil types. Collecting these data requires a lot of counting; my lab mates may be going slightly crazy after spending so many days staring through a microscope, clicking their counters.
For me, since I don’t actually have to count the samples, it has been exciting to get to know the different characters of the Dry Valleys soils. The nematodes are the major players: Scottnema lindsayae, Eudorylaimus, and Plectus. Of the three nematode genera, Scottnema (named after explorer Robert F. Scott) is the most abundant in typical Dry Valley soil. Scottnema, unlike the other two genera, is endemic to the Dry Valleys, meaning that it is found nowhere else in the world.
In more moist soils, along stream banks and next to ponds, Eudorylaimus and Plectus are abundant. Rotifers and tardigrades are not as plentiful as the nematodes, and are quite exciting to spot in the scope. Tardigrades, affectionately known as water bears, are especially cute.
So what are my lab mates looking for through the microscope? Nematodes are identified by size, the morphology of the mouth region and tail, and the general shape of the body. For instance, Eudorylaimus is much bigger than the other two genera, while Scottnema is distinguished by a crown-like mouth region.
After they identify the genera, the next step is to identify the type of individual: live or dead, male or female, juvenile or adult. In a split second, a click is made and the tally of individuals goes up. (As I type this, I’m listening to a pleasant background clicking noise of Sabrina counting a sample.) So far the record is 1423 nematodes in one sample – and that’s just from 100 grams of soil!
These little critters, so abundant in a seemingly lifeless environment, are incredibly tough. They have to be, to survive some of the harshest conditions on the planet. Not only do these microscopic organisms have to survive extreme cold, but they also have to contend with extreme aridity. Indeed, some of the most closely related species to the Dry Valleys nematodes are found in hot deserts, where they use the same coping strategy to deal with the lack of water: anhydrobiosis. In an anhydrobiotic state, a nematode’s entire metabolic system has shut down; the organism can wait indefinitely for more favorable environmental conditions. Without such an effective strategy for dealing with the lack of liquid water, these organisms would be unable to survive in the Dry Valleys.
As the Wormherders continue to count the samples, I’ll be sure to post pictures of any interesting finds! Many thanks to Ashley Shaw and Dr. Martijn Vandegehuchte (both from Colorado State University) for sharing their nematode knowledge and helping me to take the photos!