Recently, a study showed that Chlamydomonas were capable for forming multicellular structures when under predatory pressure. Basically, scientists let loose some hungry Paramecia into Chlamydomonas territory and things got stressful. I wanted to write a post about this because 1) you’ve seen me post videos and pictures of these microorganisms before and 2) it’s important to straighten out some misunderstandings about the results and how it was reported.

A Paramecium

Under the threat of predation, Chlamydomonas, usually flagellated and single-celled, will begin to form multicellular structures. Even after the threat was removed, they remained “multicellular organisms”, though I prefer to call them “advanced colonies”. There were two types of these multicellular structures: identical cells (aka: originating via mitosis) in the extracellular matrix goo and daughter cells encased in the cell wall of the parent cell (these are called palmelloids). One important thing to note is that not all the Chlamydomonas became multicellular; in fact, only two of the 5 test tanks showed these more complex forms.

Chlamydomonas: Can you spot the ones in the middle of mitosis?

You’d think that getting to multicellularity would be difficult, but it looks like the Chlamydomonas were able to do so with relative ease. This probably means that there’s already something in their genomes that’s built-in to allow them to form these palmelloids as a defense mechanism. So what’s the significance of this study? Well, it adds another element and perspective to the question, “What was the magical spark that made multicellular life happen?” I purposely wrote this article (and pretty much all the posts on this blog) with a tone of skepticism because in biology, there are no straight answers, no hard fast rules, and there are always exceptions. The headlines for this particular study are a bit misleading (just Google: single to multicellular and scroll), so I hope this post clears some things up for everyone.

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