Hm, above PMID is misdirecting, sorry. Was referring to "A comment on the origin of the vertebrate eye" by P. Satir

does not work currently. Please see Fig3 and corresponding section in our manuscript too😊
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Different homologies between amphi. and vert. photosensitive structures have been suggested over the decades (e.g. PMID 11135183 and refs), but in amphi. there's no evidence for both ciliary and rhabdomeric components in a single structure. As such, a 1-to-1 w/ either retina or pineal likely..
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Although urochordates are closer to vertebrates and can illuminate many questions on evolution (e.g. PMID 39443803), they have followed quite wild trajectories (e.g. PMID 25008364) and likely retain only rudimentary photoreceptive clusters.. no co-presence of rhabd.-ciliary, so hard to homologize

Hi, thanks so much for your (spot on!) comments and your interest in the field! 😊 In the manuscript, we do touch on cephalochordates and urochordates, albeit not extensively. Let me answer to your comments below separately:

Extremely grateful to @wellcometrust.bsky.social @vetenskapsradet.bsky.social @erc.europa.eu @hfspo.bsky.social @ukri.org @leverhulme.ac.uk @thelisterinstitute.bsky.social for their generous support of our eye evolution endeavours 👁️🦗🐋

So the retina wasn’t built de novo.

Instead, it is likely rooted in an ancestrally median, already complex eye — lateralized & rewired to solve early chordate sensory challenges.

More here:
www.biorxiv.org/content/10.1...
and curious what you think!

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..with a huge payoff, in gradual steps:
✅Choice of right depth
✅Body Posture
✅Visually - guided locomotion, eventually

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Because ambient light is messy — especially underwater.🌊

By shifting photon-detecting circuits sideways, you tune them to visual light gradients → disentangling confounding variables..

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But why lateralize an already complex median eye? 🤔

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But what if the sequence is backwards?

We argue that
bipolar cells were there 𝑒𝑎𝑟𝑙𝑦 — integral parts of parallel
microcircuits in a median eye.

And strikingly,
already in two flavors: 𝐎𝐅𝐅 and 𝐑𝐨𝐝-𝐎𝐍!

4/n

The glue? Bipolar cells.

Long seen as a late innovation — the key step from proto-retina ➡️ modern retina that boosted complexity & computation.

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Most bilaterians keep photoreceptor types separate.
But vertebrate eyes are a mash-up:

🪡Ciliary (rods & cones) and
💈Rhabdomeric (ganglion, amacrine, horizontal)
…all packed into a multilayered circuit.

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Huge congratulations Idoia!! 🎉🦈