Save the date! First Zebrafish meeting in the UK. 10 - 12. September 2025 in Exeter. @eu_fish @InfoIzfs

Thanks to to all involved and the funders !@wellcometrust @LeverhulmeTrust @UKRI_News @ListerInstitute @ERC_Research

Tons more where that came from in the paper. Dig in for imaging, cone ablations, cool behaviour (including outdoors!) and a bunch of musings.

By contrast, the ancestors of all other tetrapods stayed in or close to the water for much longer, which probably allowed them to come up with new uses for this ancestral regulatory system. So they managed to integrate it into their now terrestrial eyes.

Birds, reptiles and amphibians all still have it. What is the difference? Looks like the ancestors of mammals were much quicker to fully move to the land where the ancestral green/blue suppression was probably a bad thing, so they lost it.

We think that our findings on fish have critical implications also for other lineages, in particular mammals, the only major terrestrial vertebrate lineage that is lacking the ‘regulatory’ green/blue system.

The green/blue system of fish is highly sensitive to this change: Largely silent under ‘white’ light (because their colour opponency suppresses activity) but active under green/blue light.

This is key: In the water, spectrally broad ‘white’ light only exists in the foreground. In the background, spectral interactions of light with water mean that the image becomes increasingly monochromatic (i.e. green/blue).

The antagonistic input architecture to the fish eye can in fact already be seen without manipulations: Fish have a massive ‘white bias’. Show them spectrally broad stimuli and their brain lights up like a Xmas tree. Show them ‘non-white’, and you get a subdued response

By contrast, if we kill red or UV cones, vision is not fine.

In fact, if we kill green and blue cones, fish vision is fine. More than fine, in fact. It becomes less variable, because the green/blue system hangs in a delicate and mutually antagonistic balance.

To do so, their outer retina is fundamentally set up to contrast the signals from the colour opponent green and blue cones (which are lost in mammals) from those of red and UV cones (which are retained).

Nope! Not ancestrally. We show how that (zebra)fish, which retain the ‘original 4’ cones, ‘use colour information’ to auto-subtract the underwater background before the visual signal ever gets to the brain.

Rods give greyscale vision, but cones are for colour, right?

New @bioRxiv #preprint with @chiara_fornetto and T Euler (who left X): https://t.co/b0otvB12ap

Are people moving to bluesky? I just made an account… @Neurofishh.bsky.social

We are looking for a new lab administrator (based in Brighton, UK). This is a 50% position, and it is largely admin & computer based. It does not necessarily require a science background. Anyone interested please get in contact and/or apply here:

Thanks to all involved, especially @TommasiniDario who really drove this one!

How might they have evolved? We posit that they could be the result of a 'failed split' in the precursors that normally lead to red cones. Red singles normally develop in twos that separate, so duplicating the pre-split state could reasonably give a red-red double cone.

Also, double cones are in the "infrared" part of this manifold. They are 'redder than red'. Makes sense, looks like they take over a lot of red-cone tasks in species that have them (discussed in Baden 2024 NatEcoEvo and Baden 2024 PloS Bio)