How could you not love an organism that manages to combine both slime and mould? Slime moulds are saprobic organisms (i.e. they gain their nutrients by breaking down dead organic matter) that spend most of their life cycle feeding as separate amoeboid cells or disaggregated plasmodium. However, when conditions become right all the cells or plasmodium near each other will stream together to form a fungus-like fruiting body that releases spores, as shown in the diagram above borrowed from here. Because slime moulds thus resemble protozoa for part of their life cycle but fungi at other times, they were an early protagonist in the destruction of the idea that all organisms could be divided between plants and animals. Slime moulds, it turns out, are mostly not related to plants or animals. As our understanding of organismal phylogeny has progressed, it has become clear that not all slime moulds are even related to other slime moulds. Instead, the term has been used to cover a number of phylogenetically disparate organisms with little in common other than similar life cycles. However, the majority of references to slime moulds out there fail to mention this, focusing on only a small part of “slime mould” diversity, so I thought I’d give a brief overview of the full diversity of organisms with a slime mould-type life cycle.
One of the really wonderful things about attending CalTech was the opportunity to have Leading scientists, even Nobel Prize winners teach the undergraduates. In my freshman year introductory biology class we had a lecture by Max Delbruck, shortly before he retired.
As the physicists had Feynman, the biologists had Delbruck. It was a very memorable lecture because he talked about slime molds. I had never heard of them and could not really understand why someone of his stature was studying them.
By the end of the lecture, I was fascinated by them. It is nice to get a chance to get reacquainted.
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