Thursday, December 01, 2005

Slime Molds

Fuligo septica: The 'Dog Vomit' Slime Mold

Another one of my favourite Don Valley creatures. The one pictured here was photographed on a wood chip pile at the Brick Works.

This year I signed up for a university course in botany because I am interested in the study of plants. For the first two months of the course they talked exclusively about all the life forms that aren't plants but are studied by botanists. These are mainly algae and fungi. Then there are the things that are neither fungi nor algae. Nobody knew how to classify them so they gave them to the botanists. These are the slime molds. They have characteristics similar to fungi but have some characteristics that make them rather unique. For one they have the ability to move around, something that no fungi can do. There are about 700 to 1000 species currently known. Most occur in temperate regions like Canada.

The slime mold pictured here is Fuligo septica, also known as the Dog Vomit Slime Mold. It is an ugly looking mass of yellow or orange stuff that does sort of look like something the dog left in the backyard. In fact this creature is in a state called the plasmodium, an amoeba-like mass of protoplasm that moves by pushing out pseudopod fingers of plasma.

They are often found on piles of wood chips or mulch. They feed by ingesting woody material. This is different from fungi which feeds by absorption. When conditions become too dry they form a resting state called a sclerotium. One reason that they were once thought to be fungi was due to its reproductive cycle. It uses spores to reproduce. When the time is right it sends out masses of spores from pods called sporangia. This is similar to the way fungi reproduce.

Fuligo septica in a quasi-hibernation state

My botany course lecturer, a mycologist, told an amusing anecdote about slime molds. Way back in the 1960's, Americans were experiencing a rash of UFO sightings and rumours of alien invaders were common. Apparently slime molds can grow quite large in ideal conditions and one day someone spotted a monster slime mold several square metres in size in their backyard. They called the police and when they arrived they thought it was some sort of alien from outer space. Their response was typically American: they shot it!

Where do slime molds fit into the ecosystem? They belong to a class of creatures known as detritivores. They process dead plant and animal material and turn it back into elements that can be reused. If they didn't perform this vital task we'd be neck deep in crap in no time at all! So next time you see this little critter don't cringe in fear, it's one of the good guys.

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