domingo, 13 de enero de 2013

The Blob Attacks: Gooey Slime Mold is an Example of Leaderless Motion

ORIGINAL: Decoded Science
OCTOBER 29, 2011

"Dog Vomit" slime mold is also known as Fuligo septica. Image Credit: Interro
It’s creeping, creeping, creeping toward a log near you. Perhaps it’s hanging out in the bark mulch, slowly eating its way along. The blob is here in the forests around you, and its name is slime mold.

At first glance, a slime mold appears to be a very unassuming collection of slimy bits that are often brown or yellow. It can look rather unfortunate. One of the world’s most common slime molds is also known as the “Dog Vomit” slime mold.

What Are Slime Molds?
For a long time, slime molds were identified as fungi. They appear to be fungi. They sit on a log, munching away on detritus rather than making their own food. They reproduce through spores. However, there is one big difference between slime molds and fungi: slime molds move.

A moving plant? Or is it an animal? Well, slime molds find those human-created categories to be inadequate to their amazing cellular properties. A slime mold streams over bark and leaves, engulfing them. While it moves like an animal, it acts like a fungus. A slime mold consumes dead material. However, a slime model does not have hard chitin in its cell walls, so it’s able to get together in large cytoplasmic masses.
Unlike fungi, slime molds do not have hard cell walls. Image Credit: stoon
What is a slime mold, if not a fungus? The slime mold is made out of a conglomeration of single-celled life forms called protists.

Different Types of Slime Molds
Some slime molds are naturally gregarious. Plasmodial slime molds (cue Ghostbusters soundtrack) consist of single-celled slime molds that get together in a cytoplasm gel.

Other slime molds use the social media of the slime world to get together and have a feeding frenzy. These cellular slime molds are called slugs when they are alone. Each slug leaves a chemical trail as it moves around a log. When a slug encounters another pheromone trail, it follows it. Eventually, the slugs all get together in an area that is optimal for feeding.

When slime molds get together, the party begins. They form a structure called a pseudoplasmodium that moves over logs, bark, and soil at a rate of one inch per day. When food is particularly abundant, the slime mold changes. Some of the slugs form a base, while others become spores and stalks. The slime mold forms reproductive structures as a whole organism, even though it is made out of individual parts.

Slime Mold Motivations
Slime molds are relatively simple. Each slug seeks the same thing: namely, food. They also need moisture to survive. They can communicate their success to other slugs, and this chemical communication ultimately results in a collection of slime mold cells that becomes something quite different from its parts.

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