Tuesday, 18 February 2014

Slime mold hardly dog vomit or scrambled egg


These pink blobs in Melbourne's Royal Botanic Garden are slime molds (or moulds). They are not fungi, or for that matter algae, plants or animals.

'Slime molds' is not what we call a natural group. That is, organisms called slime molds aren't the only descendants of a common ancestor. Natural groups are things like flowering plants, primates and Entwisleiales. Unnatural groups are things like algae, trees and cuddly animals - these are terms of (sometimes great) convenience.

The slime molds can be divided into various convenient, and some cases natural, subgroups. The plasmodial slime molds (or Myxogastria) are microscopic, often swimming (they can have flagella) cells that fuse together to form a great big cell with thousands of nuclei (each one the 'brain' of the single swimming cell). The big cell, the slimy moldy bit, is called the plasmodium. These you can keep calling slime molds.

The cellular slime molds (or Dityostelia) are microscopic non-swimming cells that only every now and then aggregate into a 'slug', called a pseudoplasmodium. Unlike its plasmodial colleagues, the individual slime-mold cells maintain their integrity and the slug is a little like a many-celled organism such as mushroom, rabbit or...slug. They are better treated as 'social amoebae' rather than slime molds.

There are other smaller groups, more or less related to these two. The slime nets (or Labyrinthulomycetes) are these days not to be mentioned in the same sentence (apart from here) as the slime molds. These mostly marine creatures consist of tubes along which cells glide along looking for food. The slime nets are related to, and possibly part of, the Heterokontophyta, which includes diatoms and kelp (algae) and phytophthora (water mold).

All of these organisms produce spores when things get tough. Sometimes the spores are clustered on the top of a stalk, other times in round puff-ball like structures like these (at the end of my forefinger).


This particular slime mold is called Lycogala epidendrum, a plasmodial type. It's growing in a pot of Swainsona in the nursery at Melbourne's Royal Botanic Gardens. The picture at the top of the post was taken by David Robbins, a few weeks before I saw and photographed them in early January.

A few weeks before David Robbins, and Val Stajsic (the Identification Botanist who lived up to and extended his job title by identifying it as Lycogala epidendrum), saw it these fruiting bodies called aethalia, the slime mold would have consisted only of tiny red cells. I think the fruiting body is the entirety of the plasmodium stage in this case.

Those slime molds that form big slimy masses of various kinds - dog vomit, red raspberry, scrambled egg, wolf's milk - can cover up to a square metre or so in some species. They not only spread but move, being able to track down food (bacteria, yeasts and algae) or repel themselves away from something nasty at a rate at least 10 times faster than a plant. Not quite your typical animal speed but fast for a slimy mass I'm sure you'll agree. Our slime mold just stayed where it was, in the pot.



Notes: Information sourced from among other places University of California Museum of Paleontology, The Eumycetozoan Project and an article published in the Proceedings of the National Academy of Sciences of the USA on the origin and evolution of slime molds by Sandra Baldauf and Ford Doolittle. This mention of Doolittle reminds me that a slime mold shouldn't really be part of TalkingPlants (or TalkingAnimals to be fair) but I'm willing to include anything that is rather sluggish and grows in a pot...

9 comments:

Dan Murphy said...

Since learning about these during mycology classes at uni, I have always been amazed by how the free-living cells aggregate into multi-cellular forms with recognisable morphology. Nice post Tim.

Dr. Ricky said...

Oh my, Sandy Baldauf is a great reference for the early diverging eukaryotes, but we have come a long way with the molecular phylogeny since 1997. In fact, the dictyostelids shouldn't even be called slime molds at this point - they're clearly social amoebae. The classification has long been updated - the term slime mold was an old system that tried to cram together some very distantly related organisms just because they sort of look like each other.

Tim Entwisle said...

Thanks Dr Ricky. I realise things had changed a lot but found that the term 'slime mold (or mould)' was still being used for these other groups. As I say, far from a 'natural' group and just a term of convenience, or perhaps inconvenience for scientists! I've edited slightly to pus the dictyostelids a little further away....

Tim Entwisle said...

Thanks for comments Dan!

garry Z said...

do you think these will grow in florida?

Tim Entwisle said...

Yes this organism grows all over the world, in various climates, so should be some in Florida. That said, you don't see them that often - unless you are looking for them!

garry Z said...

Oh thank you for the quick response. I actually thought I was commenting on another article, but this article was going to be the next anyway ha!

I have found some weird slime mold growing in a spot in some woods in central florida. I thought at first it was animal droppings, more than likely bird or bat, but the more I was investigating it closely I realized it is some kind of slime mold producing like crazy in this certain spot.

Your fuchsia post caught my eye im going to link it at another site.

Tim Entwisle said...

Ah, no problem. Did wonder whether you wanted to grow for find these things!

dog training said...

I think the things you covered through the post are quiet impressive