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What creeps and crawls, has no brain, but is intelligent?

By: Alissa Brown

It lurks beneath your feet. It hides in the dark. It swallows its victims whole. It is slime molds—the perfect holiday topic of conversation, right?  OK, so maybe we do not typically discuss slime molds at holiday parties, but just look how festive and yes, pretty, slime molds can be….

Slime mold.
Image courtesy of Matt Goff.

These introverted creatures date back almost one billion years and are relatively simple in structure. Evolutionary biologists think slime molds evolved from soil amoebas and were likely early terrestrial pioneers, inhabiting the land even before plants or animals. Slime molds exhibit seemingly extraterrestrial characteristics. These amoeba-like creatures begin life as single-cell organisms whose cellular bodies travel in soils toward food sources, creating a neuron-like shape with elegant filigrees.

Slime Mold, Diachea leucopodia.
Image courtesy of Alain Michaud, The Eumycetozoan Project.

To eat, the slime mold’s cytoplasmic movements engulf food items whole by pulling them in to the cell. This process is called phagocytosis: phagein meaning to devour, kytos meaning cell, and osis meaning process.

Sound familiar? Perhaps the creators of The Blob were slime mold fans. After all, they fashioned their lead antagonist as a formless, gelatinous mass engulfing any and all creatures unwitting enough to stand in its path. Fortunately, humans need not fear the hunger of the slime molds—their favorite entrees are bacteria, protists, true molds, fungi, and dissolved organic materials, all found on and around decomposing plant material. As a result, slime molds are primarily found in forests, mulch, and dead plant material in gutters.

Chocolate tube slime mold, Stemonitis splendens.
Image courtesy of Blue Jay Barrens.

When food sources are scarce, individual slime mold organisms may clump together, forming a single, multicellular organism, sometimes encompassing tens of thousands of cells. The newly formed organism travels up to the soil’s surface to wait for a mode of transportation (either an animal or rain) to carry it to a more suitable environment. At the soil’s surface, the various cells perform different functions. Some cells become stiff stalks, others climb to the top of the stalk and become sticky balls, while others protect the health of the organism by searching for and destroying harmful bacteria.

A unique characteristic of slime molds is its ability to reconfigure itself into two separate functioning organisms if the multicellular groups are separated.[1] This is useful for cancer drug research, providing scientists with multiple identical samples. The slime mold’s ability to distribute cytoplasm (the liquid part of the cell) to all parts of the organism may provide valuable insight into how cancer drugs disrupt the blood flow to tumors, thereby reducing their growth rates.

The beauty of the slime mold is found in its fruiting body. When it is time to reproduce, the slime mold discharges appendages that release spores containing reproductive material, transforming the slime mold into various shapes and colors. Check out the NY Times slideshow, Beauty and the Blob, showcasing some of the vibrant shapes and colors of slime molds.

Despite being single-celled, slime molds exhibit highly intelligent characteristics, including memory and learning capabilities. Even though slime molds do not have brains, researchers in Japan found they are able to remember and anticipate repeated, lab-controlled events. In addition, slime molds find the most efficient path to navigate to food sources. Bioengineers studying the branching patterns and movements of slime molds are intrigued by their mobile efficiency. In one particular study, computer scientists Andy Adam­atzky and Selim Akl placed slime mold on a map of Canada and deposited oat flakes on Toronto. To move toward the food source, the slime mold’s branching patterns closely mimicked the existing Canadian highway system.[2] The study was replicated in several cities across the world, each producing similar results. Watch the YouTube video of the experiment.

Slime mold’s precise network towards food sources mirror those of a network engineer.
Image courtesy of Andrew Adamatzky.

Slime molds leave behind a sticky trail so they avoid traveling the same path twice. What’s the big deal? Adamatzky believes the mapping capabilities of slime molds can “design roads, wireless networks, and information-processing circuits better than today’s computers.” (Baer, Adam. Why Living Cells Are The Future Of Data Processing.)

So where do these seemingly intelligent, yet simple organisms, come from? They were discovered relatively recently, about 140 years ago.[3] The have virtually no fossil record and take on characteristics of multiple taxa. Initially, taxonomists considered them fungi, but today the two groups are considered unrelated. Although their evolutionary roots may still be uncertain, it is obvious that these fascinating, colorful, unique organisms are an important component of our ecosystems.

 

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