Yeah! The nidos are a bit weird because the Mesoniviridae (insect-infecting) are the only known invert group to use Class I, and their sister group (Medioniviridae- tunicates and marine inverts) use Class II/"toga-like". I don't know what that means for the Mesonis.

Oh wow, thank you!

Tl;dr Tunicates are amazing, and you should care about them or at the very least care about their viruses.

They teach us about the ancient evolutionary history of our own viruses through virus-host co-divergence and demonstrate the role that recombination has played throughout that history.

What’s more is that glycoprotein usage is not congruent with our Nidovirales polymerase (RdRp) phylogeny, suggesting a complex history of glycoprotein switching throughout this order.

Our patchyvirus is not alone in its propensity for glycoprotein switching. We knew that some tunicate nidoviruses had toga-like glycoproteins (“Tognidoviruses”, Buck, et al., eLife, 2024). We found even more nido-like viruses with Class II (C-II) fusion proteins. The heat map shows FoldSeek probs.

But it’s not always so straightforward. We found a (-ssRNA) paramyxo-like virus that has a (+ssRNA) toga-like glycoprotein (blast results in table).

I have unofficially named this (maybe) new family the Patchyviridae after Patchy the Pirate from Spongebob. Thanks to my cousin David for that one.

We also observed this pattern in the novirhabdoviruses (which can make fish sick) and alphaviruses, again in red:

Answer: yes, and we think so.

We found multiple instances of influenza-like viruses in tunicate metatranscriptomes (shown in red) that fell towards the base of the clade. Here is the phylogeny for PB1, but the pattern held up for the other segments, too.

It turns out that not much is known about tunicate viruses.

And so we asked: Can we find relatives of vertebrate-infecting viruses in tunicate metatranscriptomes? That is, could the history of some vertebrate-infecting lineages actually date back to basal (invertebrate) chordates?

They might not look like much on the outside, but these guys can have a full complement of organs (and even friends!) inside. Importantly, as larvae they are free-swimming “tadpoles” that have a notochord, which makes them basal chordates.

Some background. We, along with every other vertebrate, are members of the Chordata – we have a spinal cord. But not all chordates are vertebrates! Meet: tunicates, our closest invertebrate chordate relatives.

This was another great collaboration with @grovearmada.bsky.social, @rhyshparry.bsky.social, the USyd team @eddieholmes.bsky.social and @jonathonmifsud.bsky.social, and non-bluesky users