Microscopic Carnivores

Up to now, we've concentrated on those carnivorous plants that can easilv be grown, cared for, and watched as they demonstrate their marvelous skills.

But there are others that most people never see and few know exist. These too are quite carnivorous. Their strength is equal to the iron grip of the flytrap or the octopuslike clutch of the tentacled sundews.

Consider for a moment how powerful plants really are. The most slender root of a tree can work its way through the smallest crack in a rock ledge. It grows cell by cell. Eventually it can establish a sturdy roothold for that tree. You've seen this many times, trees jutting out from seemingly impenetrable rock cliffs along roadsides. Even grass, especially those weed grasses, prove their power many times. You may asphalt a drive, onlv to find some plants still forcing their way through what should be permanent impenetrable paving.

So it is not difficult to realize that some of the microscopic carnivorous plants also may have amazing strength. For example, there are many types of soil fungi in the plant kingdom. Admittedly they are quite primitive. Some of these have evolved a carnivorous pattern as the larger carnivorous plants have done. These fungi also have developed different ways to lure and catch their microscopic meals. Some have sticky discs to which tiny soil bacteria and nearly microscopic worms become stuck fast. Others have perfected nooses. Thev don't actually lasso their prey; instead, they beckon tiny soil eelworms, called nematodes, with their own versions of aromas and secretions. At least, that's how the agronomists and botanists we've talked with see it. As the nearly invisible worms crawl through the noose or hoop, these fungi sense they have a catch. The cells contract until they contact the unsuspecting worm. Thus, the fungi tightens the noose, effectively preventing the prey's escape. Watching this bizarre phenomenon requires keen eyes, a high-power microscope, and hours of patience.

Two of the smallest types of carnivorous plants belong to a group of fungi called molds. You can often find them in a bit of garden compost or the decaying leaf mold from a forest floor. When you place this sample under a microscope, there's lots to see. If lucky, you may have a portion of these carnivorous fungi. Their diet can also be revealed with proper magnification. Try 50 to 100 times at first. Once you locate the appropriate loops and snares you can zero in at higher magnification for a better picture of what is taking place.

Amoebas, nematodes, small crustaceans, and rotifers are all at work in typical compost or rotting leaf humus. They are the diet of these nearly microscopic carnivores. Nematodes seem to be the preferred food. Nematodes are tiny worms, about I/io >"'" long. Some are helpful; others, like the golden nematode and potato wort nematode, are disaster when they invade farm fields. They stunt and kill the crops. You may have seen cabbage, broccoli, or cauliflower plants that are stunted, or dead. Chances are the root knot nematode has been at work. Fortunately, carnivorous fungi don't seem to discriminate. They eat all the nematodes they can catch.

One of the simple carnivorous fungi looks like a twig with tiny globules sticking out along its sides. Biologists have called it a "lethal lollipop." It is scientifically called Dactylla asthenopaga, quite a mouthful to say for such a tiny, primitive plant. When a nematode comes wiggling along and touches the knobs, it sticks to them. The more it squirms and wiggles the more its body touches the first and eventually other knobs. Scientists who have studied these primitive plants in action report that after the victim is effectively glued to the knobs, spearlike filaments are inserted into the worm's body. These serve to digest and absorb the "eel" dinner, leaving only the outer skin.

Another, even more ingenious fungus literally snares its meals. Dactylaria gracilis is a mold which grows nooses along its length. They may look like microscopic donuts, but these "donuts," of course, aren't to be eaten. They do the eating of anv little nematodes or other creatures that crawl or move through the hole in the middle of the "donut." Each noose or snare has three cells which form the loop. They are joined to the stalk by a one-celled stem.

The outside of the snare seems lacking in response. Nematodes mav touch it and provoke no reaction. But when the worm pokes its head through the noose, intending, I suppose, to crawl right through without a worn,', then the fun begins. Fun for the plant, that is. Within a fraction of a second these three little cells change drastically. They swell several times in volume. In effect, this tightens the noose, putting a powerful hammer lock on the victim. As the victim struggles, prongs similar to those of the lethal lollipop are extended into the worm's

An eelworm caught by Dactylla asthenopaga (left) and D. gracilis.

body. They do the final job of absorbing and extracting the nutrients from the worm for the plant.

Although these carnivores prosper within soil containing nematodes, they can survive just on decaying organic matter. In this respect, they and other carnivorous fungi are like the larger insect-eaters. They can survive quite easily without a plentiful supply of insects or worms.

If your interests in carnivorous plants extend underground to those microscopic forms, you can actually stimulate these little critters to perform for you. The loop fungus is especially cooperative. Without nematodes in the soil, it merely grows steadily on without the loops. Or, at least, only a few tentative feelers. However, when you obtain some decaying organic matter or soil that contains nematodes, you can watch the plant go to work. By looking over samples gathered in your travels you can probably find some nematode soil, especially in gardens where cabbage, cauliflower, and their relatives show symptoms of root knot nematode damage. At this point, take the soil and mix it with a bit of water, enough to moisten the soil. Then, combine the soil with the organic matter which contains your carnivorous fungi friends. Day by day, through the microscope, you'll see the lethal loops begin to grow. From then on, keep an eye open. As the nematodes wiggle about, you'll eventually catch the action in the lens.

You can continue studies of these carnivorous fungi by cultivating them and microscopic amoebae and nematodes in agar solutions in petri dishes.

In a report printed in 1934, Charles Drechsler of the Bureau of Plant Industry outlined some interesting studies. You too can conduct similar tests. He noted that fungi on a natural substratum, their native habitat, often only reveal typical plant growth. But, he points out, very probably because nematodes and amoebae multiply actively and freely in agar plate cultures, the unique activities involving these animals as prey and the fungi can be more frequently seen. He identified two species of testaceous rhizopods, Diffugia globulosa Duj. and Trinema enchelys Ehrenb. These are both shelled protozoans, sluggish in movement. Not too sluggish to resent their entrapment by the fungi, of course. The plants appear to just wait, but as the protozoans move through the agar culture thev become caught by the plants. On closer observation, the actual snaring can be seen, with the minute animals penetrated by the plant during the digestive process. All this must be viewed through the microscope, but in that normally unseen world the prowess of the carnivorous plants is apparent. Those that catch and eat animals are readily seen to increase in size. Probably in health, too, when they are better fed.

During his extensive studies, as reported in the Journal of the Washington Academy of Sciences, Vol. 24, no. 9, Mr. Drechsler noted that other minute plants also have the carnivorous habit. He mentions trichothecium, dacty laria, arthrobotrys, dectylella, and monacrosporium among the nematode-capturing species.

Other scientists in field and lab have expanded on these studies. It would seem that although most carnivorous plants exhibit their wonders aboveground, visible for all to see, nature's mysteries also abound in the soil, well hidden from the naked eye.

As you expand your explorations of the weird world of carnivorous plants, don't just look around. There may be just as many fascinating surprises down below, right beneath your feet. True, a microscope may be necessary. But on the trail of carnivorous plants, as we have been for many years, new worlds of wonder can be found in the most unlikely ways. And places too.

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