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Please see Glossary for definitions.
What are slime moulds?
A slime mould is a large mass of live slime. It grows to find food by extending tendrils of slime, and when a tendril comes into contact with a food source, the slime mould will thicken that tendril and grow more tendrils over the food source. The slime mould will feed off many food sources, and it will create a network of nutrients by connecting the tendrils with slime. This makes the fan-shape seen below.
Credit: Discover Magazine
This slime mould is looking for food sources and it searches in a fan-shape, with vein-like tendrils connected to the main body of the slime mould and the thicker tendrils are connected by smaller tendrils.
Types of slime moulds
There are many different types of slime moulds, but for my project I only studied one. I studied Physarum polycephalum, which belongs to the class Myxomycetes and the genus Physarum. Here is the full classification of Physarum polycephalum:
Domain: Eukarya
Kingdom: Protista
Phylum: Myxomycota
Class: Myxomycetes
Order: Physarales
Family: Physaraceae
Genus: Physarum
Species: Physarum polycephalum
There are over 700 different known species of slime moulds.
Slime moulds fit in the mycetozoan group of the amoebozoa. Mycetozoa includes the following three groups:
Myxomycetes (or Myxogastria): acellular (plasmodial) slime moulds - e.g. Physarum polycephalum
Dictyosteliida (or Dictyostelids): cellular slime moulds - e.g. Dictyostelium discoideum
Protosteloids: amoeboid slime moulds that form fruiting bodies: these are much smaller and have characteristics of both of the other two groups. Their fruiting bodies only form 1-2 spores - e.g. Protostelium mycophaga
Acellular vs Cellular slime moulds
The most commonly found type of slime mould is the acellular, or plasmodial, slime moulds. They can be found anywhere in the world and are generally found in dark, woodland areas on logs or mulch. Acellular slime moulds are also known as 'plasmodial' slime moulds because they are mostly seen in their plasmodial 'feeding' stage which looks like a large mass of slime. In fact, the plasmodial slime mould Fuligo septica is more commonly known as the 'dog vomit slime mould' or 'dog vomit fungus'.
Fuligo septica - Dog vomit slime mould
Credit: smallrooms
When the plasmodium is in its feeding stage, it will 'crawl' across its environment at an average of 1cm per hour (the top speed of a slime mould is 4cm per hour), and can grow up to several square metres. Slime moulds can also weigh up to around 20 kilograms (44.1 pounds). That's as much as 10 bags of sugar, or an adult elephant's heart.
Although cellular and acellular slime moulds are very similar, there are some differences in their life cycles. The diagrams below show the life cycles of both types of slime moulds.
The zygote divides by mitosis in prophase, metaphase, anaphase and telophase, but does not perform cytokinesis. This results in many nuclei in one large cell.
As you can see from the above diagrams, an acellular (plasmodial) slime mould is just one giant cell, but a cellular slime mould is thousands of small cells compacted together. The individual cells in cellular slime moulds all work independently, but they all work together towards the main cause. This is where the main difference between the two types lies.
Slime moulds are brainless
Regardless of their type, slime moulds have no brain. No slime mould possesses a single neuron. This is what makes slime moulds so interesting - this combined with the fact that slime moulds display a primitive form of cognition. How can brainless slime make intelligent decisions, and remember them?
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