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

7/n

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 👁️🦗🐋

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.

2/n

We will peer across a 500 million year chasm of convergent evolution to discover how high resolution camera eyes in cephalopods and polychetes function without the elaborate local circuitry found in the vertebrate retina.

I do not find the chromatic aberration hypotheses from the lens or pupil to be particularly convincing. The chromophore swapping and tiered retina in firefly squid seems to be the best shot at color vision in cephalopods. Perhaps there are more systems like that in other species.

I always liked the idea that they use chromatophore pigments as spectral filters for photoreceptors in the skin to detect environment color, but hasn't panned out. I think they are not matching color, but simply evolved chromatophores suited for their habitat and they just adjust contrast patterns.