Ferris Jabr in Scientific American:
Something scientists have come to understand is that slime molds are much smarter than they look. One species in particular, the SpongeBob SquarePants–yellowPhysarum polycephalum, can solve mazes, mimic the layout of man-madetransportation networks and choose the healthiest food from a diverse menu—and all this without a brain or nervous system. “Slime molds are redefining what you need to have to qualify as intelligent,” Reid says.
In the wild, P. polycephalum rummages through leaf litter and oozes along logs searching for the bacteria, fungal spores and other microbes that it envelops and digests à la the amorphous alien in the 1958 horror film The Blob. Although P. polycephalum often acts like a colony of cooperative individuals foraging together, it in fact spends most of its life as a single cell containing millions of nuclei, small sacs of DNA, enzymes and proteins. This one cell is a master shape-shifter. P. polycephalumtakes on different appearances depending on where and how it is growing: In the forest it might fatten itself into giant yellow globs or remain as unassuming as a smear of mustard on the underside of a leaf; in the lab, confined to a petri dish, it usually spreads itself thin across the agar, branching like coral. Biologists first brought the slime mold into the lab more than three decades ago to study the way it moves—which has a lot in common with they way muscles work on the molecular level—and to examine the way it reattaches itself when split. “In the earliest research, no one thought it could make choices or behave in seemingly intelligent ways,” Reid explains. That thinking has completely changed.