This is a gruesome example of how nutrients can move through the soil food web. Drawing this scene was complicated and very challenging, but I learned a lot in the process. The other soil life illustrations took about 10-15 hours each, this one took 32 hours over the course of several weeks. I had to leave and come back to it a few times, and I’m still not sure if it’s really finished. It might be one of those pieces that never really feels finished because there is so much to look at, but I had to draw the line (no pun intended) somewhere.
This drawing requires a bit of explanation, unless you’re a soil biologist or just know a lot about the soil food web.
The main subject of this illustration is the big worm, which looks kind of like an earthworm but is actually a nematode. Nematodes are roundworms are usually very small and are unsegmented, unlike earthworms. There are over 25,000 known species of nematodes, but they are so ubiquitous that scientists estimate there are actually about a million different species of them. If you’re an avid gardener or maintain a lawn you might have heard of nematodes before, either to help fight pests or as pests themselves. I’ve seen packages of parasitic nematodes in garden centers that people can buy as a biological pest control against grubs in their lawn.
Soil nematodes are very small; you usually need a decent microscope to see them. There are a few main types of soil nematodes that gardeners are interested in: fungal feeding, bacteria feeding, predatory, and root feeding nematodes. They have specialized mouthparts according to their diet. The nematode pictured here is a root feeding nematode, with a needle-like mouthpiece called a stylet used for piercing through plant roots to feed on them. This can cause bulges or lesions in the roots, which are not good for the plant.
The fungus pictured is Arthrobotrys dactyloides. You can find a very good video demonstrating how it traps nematodes here. I used this video as a reference to get a better idea of how the fungus should look, since I’ve never seen one in the microscope myself.
Nematodes don’t have any eyes, so they find their food by sensing chemicals in the area, kind of like our sense of smell. The fungus emits something to attract the nematodes into the rings, and when the nematode swims through the ring it senses the heat and the ring cells rapidly swell up like balloons, trapping the nematode and killing it. Then, fungal hyphae (like roots) grow into the nematode’s body and begin to digest it from the inside.
In the illustration, all this is happening on the surface of a plant root. A plant which is probably very happy to have the fungus around protecting its roots from hungry nematodes.
As usual, if you look closely you can also see some other small critters in the picture. There are two small flagellates just above the plant root between two root hairs on the left side, and a ciliate just below and to the left of the nematode’s head. There are also scattered bacteria, demonstrating just how ridiculously small bacteria are, so small that even at this scale they just look like little specks of debris.
I kept the soil background relatively simple in this drawing because it was already busy enough with all the scraggly root hairs and fungal hyphae. I wanted to make sure it was easy to focus on the nematode and the fact that it’s trapped.
I hope this drawing, along with the others in the soil life series, will help demonstrate how complex, fascinating, and alive the soil ecosystem really is. It is essential that we as gardeners or farmers take care of our soil by protecting and encouraging a diverse and thriving soil ecosystem. Just being a bit more aware of what goes on down there is the first step towards more sustainable food production on any scale.
There are still more drawings to come in this series. I’ve already started the next one, which features some of my favourite protozoa. Here is a sneak preview of the work in progress:
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