Thanks to @maitefreired.bsky.social for doing all the work, to @bastinlab.bsky.social @beaplab.bsky.social & Nicole King for comments on the manuscript, and to @currentbiology.bsky.social for a smooth and constructive peer-review experience 🙌

... and might be especially key in confined microenvironments such as the soil, where protists are often trapped in thin liquid layers in pores between grains. (Choanos are commonly found in soil, but their ecology and motility in this environment are pretty much unknown; pic: tinyurl.com/9vh488bk)

Gliding is conserved in at least 2 choano species we looked at (C. flexa and S. rosetta). We don't know in which natural context it is deployed, but we think it is likely to be involved in interactions with surfaces such as biofilms...

Most striking, in some instances of spontaneous flagellar detachment, the flagellum can glide on its own - mercilessly leaving the cell body behind, stabbing it on the way if need be (don't do this at home).

Do choanos defy the laws of physics? Not quite. Multiple pieces of evidence suggest the motor force for gliding resides in the flagellum (like in Chlamydomonas): (1) flagellar ablation prevents gliding (2) inhibition of the molecular motors of intraflagellar transport abolish it too.

In this new study, @maitefreired.bsky.social has shown that moderate confinement activates *yet another* mode of motility: choanos straighten their flagellum, and start moving over the substrate at pretty high speed (~1 µm/sec) without any visible cell deformation. They glide!

What about choanos? They are best-known as flagellar swimmers. In 2021, we showed they are additionally capable of amoeboid motility, crawling via cell protrusions under strong geometric confinement. (elifesciences.org/articles/61037)

Gliding in diverse protists involves different parts of the cell - eg, flagella & IFT motors in the alga Chlamydomonas (pic: tinyurl.com/ye2jsbs5) - suggesting multiple evolutionary origins. Interestingly, gliding has also only been described so far in lineages very distant from animals and fungi.

Do diatoms disprove physics? Not really. They also exert a force on the substrate, but this time, the action occurs at the molecular scale: movement is powered by adhesive transmembrane proteins stuck to the substrate and coupled to intracellular molecular motors. (fig: tinyurl.com/ytd55aw5)

Even more mysterious than ducks, some protists can move over a surface without visible cell deformation: no beating flagellum, no crawling protrusions - as if propelled by some superpower. This motility is called "gliding". See an exemple in a diatoms below (www.youtube.com/watch?v=e4zL...).

(In reality, as most of us realized at some point when we were kids, ducks pedal hard below the surface.)

Like most biological problems, this one is best introduced by contemplating ducks. Ducks on a lake can seem to glide effortlessly without exerting any visible force, defying the laws of physics.