![]() StarLogo mimics the activities of groups such as ant colonies and flocks of birds. Their equations have also become the basis of the program StarLogo. ![]() The original equations were developed by two scientists, Mitch Resnick and Evelyn Fox Keller, at the Massachusetts Institute of Technology. Mathematical equations written to explain the process of slime mold aggregation have been changed slightly and used in the programming that controls some of the behavior of action figures in video games. The spore walls are smooth and contain cellulose, which is found in the cell walls of plants, but not fungi. The other slugs are transformed into spores. About a third of the slugs in in the pseudoplasmodium become the stalk. As a single mass, they act together to produce a single stalked spore-producing structure. The plasmodium is "fake" because each slug in it remains an individual even though they become glued together into a larger mass. Then, as part of preparing to reproduce, they stop eating. Eventually all of the slugs in an area gather themselves into a pseudoplasmodium. Even more slugs are attracted by the stronger concentration of the chemical. When other slugs cross the path of this trail they follow it, strenthening the chemical trail by adding to it. Each slug pumps out a chemical that leaves an invisible trail. Recent research has shown that there are no leaders. Scientists once thought that the signal that caused the slugs to aggregate was issued by a few "leader" slugs. When conditions are right, all the slugs in an area join together to create a pseudoplasmodium, a "fake plasmodium". ![]() The slugs crawl through dung, soil, rotting mushrooms, decaying leaves and other organic material at an average speed of 1 mm per hour. Cellular slime molds, the second major group of slime molds, exist as minute "slugs" during their growth phase. The cell-like structures which contain nuclei can grow into new plasmodia when moisture and temperature conditions improve. Inside the sclerotium, the plasmodium divides into "cells", each containing from 0 - 4 nuclei. This hard-walled mass protects the dormant cells inside until better conditions for growth return. If the plasmodium begins to dry out too quickly or is starved, it forms a survival structure called a sclerotium. Some spores can stay dormant for 75 years and then germinate. Spores are extremely resistant to unfavorable growing conditions. The spores are usually spherical with a thick wall that may be smooth or ornamented with pits, spines or warts. ![]() If the plasmodium is not stressed by its environment, it will produce a stalked reproductive structure that looks like a sphere or is popsicle-shaped. This makes slime molds ideal tools for scientists studying mitosis, the process of nuclear division. One fascinating thing about plasmodial slime molds is that the millions of nuclei in a single plasmodium all divide at the same time. Fungi produce enzymes that break down organic matter into chemicals that are absorbed through their cell walls, not ingested. Their ingestion of food is one reason slime molds are not considered to be fungi. The plasmodium ingests bacteria, fungal spores, and maybe other smaller protozoa. The plasmodium may be ugly to some, but it is not harmful. This giant cell moves, but only pictures taken over several days can show its progress. Physarum plasmodia are usually 3 or 4 cm ( ½ - 1 " ) in diameter, but can get to be 30 cm (about 1 foot) or more in diameter, and 3 to 5 cm thick. Unlike most cells, which have only one nucleus, this cell contains millions of nuclei. The yellow blob we notice is a huge single cell. Physarum polycephalum is a plasmodial slime mold. Mycologists have studied them for so long that slime molds are still included in mycology textbooks. They are now classified as belonging to the Kingdom Protista (Protoctista). Slime molds move, and lack chitin in their cell walls.
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