Nebraskaland

May 2022 • Nebraskaland 31 Chocolate Tube Slime Later in the day while cruising along in a UTV, Brueggeman driving, I spotted a small, white blob in the leaf litter. I shouted, Brueggemann hit the brakes, and we were treated to a slime mold, covered in low, round bumps. The round bumps were fruiting heads, just beginning to develop. Since immature slime molds are diffi cult to identify, we returned the next morning. The fruiting heads had matured overnight, turning brownish in color, revealing itself to be a chocolate tube slime (Stenomitis spp.). Chocolate tubes, also called pipe cleaner slimes, have bunched, columnar, chocolate brown fruiting heads supported by short, thin stalks. The erect columns of this specimen had already withered and collapsed into a twisted mass, preparing to release its spores in hopes of landing on moist habitat suitable for germination. A slime mold's life begins as a single-celled amoeba, emerging from a germinated, cracked-open spore. The amoeba prowls about, engulfi ng and digesting bacteria, algae, fungal spores and odd bits of organic matter. To move through wet environments, many species grow a whip-like tail to propel themselves. When the environment dries up, the tail retracts . When an amoeba is lucky enough to meet another, their bodies and nuclei fuse in a form of primitive sex. Now a plasmodium, the organism continues to feed while the nuclei inside divide until there are millions. Spread microscopically thin, a single-celled plasmodium can encompass several square yards. Eventually, the plasmodium migrates from its feeding area and perches on a high spot, such as a log, tree trunk or the top of leaf litter, where its spores can catch a breeze. Now stationary, the plasmodium transforms into fruiting bodies, inside of which the nuclei develop into spores and the life cycle begins again. Slime molds have a clever adaptation that might explain their eons-long survival on this sometimes harsh planet. When exposed to dry, cold or foodless conditions, they can dehydrate and enter into a state of dormancy lasting weeks, centuries and possibly millennia. When favorable conditions return, they re-hydrate and dormancy is broken. This strategy is especially advantageous for slime molds living in desert soils, on mountain tops and other extreme environments. Many-headed Slime During our photo expedition, Brueggemann was keen to show me a many-headed slime (Physarum spp.). Previously, he had seen its beautiful, yellow plasmodia growing vein-like on logs, leaf litter and even large mushrooms. Though we did not fi nd the slime in the fi eld, its story is worth telling. Unique among slime molds, many-headed slimes have large plasmodia, easily visible to the naked eye. Because they are easy to grow in petri dishes, they are the world's most- studied slime mold. One revelation from the lab is that the plasmodia of slime molds propel themselves by rhythmic contractions that push cell fl uids back and forth in waves from their center to their extremities. The many-headed slime has been clocked at a tire-squealing speed of over an inch per minute. Having precise control of the contractions, they can change speed, reverse direction, steer around distasteful items (think bright light or salt) and send tendrils out to explore for food and suitable habitat. Experiments show that Physarum can solve mazes in search of food. It extends tendrils on all paths until it fi nds the food, then retracts all except the feeding tendril. Later, when placed in the same maze, the slime mold can recall the correct path to its meal. In another experiment, many-headed slimes were hit with shots of cold air at regular intervals. Their response was to retract. Amazingly, they learned to expect A chocolate tube slime at Indian Cave with young fruiting heads By the next morning, the heads had matured.

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