What would you think if you saw a formless, gooey mass creeping along your lawn after a rain storm? Would you think aliens had landed if you saw these blobs climbing slowly into trees or up telephone poles?
After the unusually rainy spring of 1973, many people in the eastern United States thought exactly this. It took a mycologist (a scientist who studies fungi) to set them straight. These were slime molds, a very ancient and unusual form of Earth life.
A slime mold is invisible to us for much of its life cycle. This is not because of some alien invisibility ray, but because it spends much of its time divided into single cells which move over the ground like amoebas, too small to see without a microscope.
Growing And Growing
After certain environmental cues, a heavy rainfall perhaps, the individual cells get together, forming a slimy mass which resembles a slowly creeping gob of saliva. The blob grows as it moves, eating bacteria by surrounding and absorbing them, growing sometimes to over a foot in diameter.
In the last phase of its life cycle, the amorphous blob hardens into a more complex form. This can be very colorful, looking like a mushroom or a fungus or even like a yellow and white pile of scrambled eggs. As it hardens, it releases millions of microscopic spores which can grow into new slime mold cells.
One reason we study slime molds is because they resemble both fungi and amoebas, the most basic forms of plant and animal life. Far from alien life forms, slime molds could be an ancient link between the fungus and animal kingdoms and, as such, an evolutionary ancestor of all animal life.