![]() ![]() The individual amoebae forming the stalk make the ultimate sacrifice so that other Dictyostelium may live and perhaps reproduce. In this form the colony will wait until something – a drop of rainwater, a passing worm, the foot of a bird – picks up the spores and takes them to a bacteria-rich place where they can emerge from their shells and start their lives over. Each amoeba in the globe covers itself in a cellulose coat and becomes a dormant spore. They slide up to the top and form a globe. The remaining amoebae in the blob then take advantage of the suicide of their slugmates. Unfortunately, this cellulose also tears apart the amoebae that make it. In order to keep the stalk from flopping over, these cells must produce rigid bundles of cellulose. About 20 percent of the cells move to the top of the blob and produce a slender stalk. The back end catches up with the tip, and the slug turns into a blob. Its movements are slow – it needs a day to travel an inch – but the deliberateness of the movements eerily evokes an it rather than a they.Īfter several hours, the Dictyostelium slug goes through another change. It stretches out into a bullet-shaped slug the size of a sand grain, slithers up toward the surface of the soil, probes specks of dirt, and turns around when it hits a dead end. The mound itself begins to act as if it were a single organism. They then use the signals to steer toward their neighbors, and as many as a million amoebae converge in a swirling mound. But if the Dictyostelium in a stamp-size plot of soil should eat their surroundings clean, they send each other alarm signals. After gorging itself sufficiently, it divides in two, and the new pair go their separate, bacteria-devouring ways. Each slime mold prowls through the soil, searching for bacteria which it engulfs and digests. They are amoebae, and for the most part they live the life of a rugged individualist. ![]() Many species go by the common name of slime mold, but the ones scientists know best belong to the genus Dictyostelium. Scoop up some dirt, and you’ll probably wind up with some slime mold.
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