This work just goes to show that cool discoveries can come when you least expect them! Muscle activity revealed a whole new world of physiology and behaviour while the fly is standing still – we just needed to start looking below the surface to see it. 🧊🦵💓 (7/7)

But is this pulsing just an output, or does it actually cause movement? We increased the pulsing activity artificially by optogenetically activating the motor neuron that innervates it, causing flies to break from freezing earlier, and showing that the pulsing state can be causal for movement onset.

Pulsing of the leg heart ramped up to and preceded movement onset, implying that its beating is reflecting a state of ‘preparation’ to move. (4/7)

This activity turned out to be an accessory leg heart – the first time this has been observed in Drosophila. But the story didn’t end there, because the activity of this heart was exquisitely tuned to the behaviour of the fly. (3/7)

Thrilled to present our latest BioRXiv on brain/body interactions during defensive freezing behaviour! (www.biorxiv.org/content/10.1...). You might think that a frozen animal has, well, frozen muscle activity, right? Wrong! Underneath the still surface of a fly, something in the legs is beating… 🧵