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MultiplEye Lab @multipleye-lab.bsky.social · 13/05/2026

Added to this, the principal eyes are controlled by a separate developmental pathway to the secondary eyes, potentially decoupling loss across these two parallel visual systems. When one pair of secondary eyes is lost, the others quickly follow, possibly due to their shared developmental origins.

Diagram showng the rates of transitions between different eye configurations in spiders. Principal eye losses and regains occur readily. Losses of secondary eyes are rare, but once one pair has been lost, the rate of loss of the remaining pairs is very high.

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MultiplEye Lab @multipleye-lab.bsky.social · 13/05/2026

So why do spiders lose their eyes? Eye loss is usually associated with living in very dark environments like caves, and we did find a strong correlation between cave living and the loss of all four eye pairs. But most species missing selected eye pairs live above ground!

Figure demonstrating that eye loss overwhelming occurs within clades that have transitioned to low-light habitats. Although caves are strongly associated with complete eye loss, partial losses occur in dim-light surface habitats such as leaf litter.

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MultiplEye Lab @multipleye-lab.bsky.social · 13/05/2026

The principal eyes have been lost many times over >200 Ma, with a distinct peak in losses in the Triassic and Jurassic 🦕 Our analysis strongly suggests that the principal eyes were also _regained_ multiple times! In contrast, secondary eye losses are much more recent...

Ancestral state estimation of eye loss for each of the four eye pairs in spiders. Only the principal eyes show historic losses, which occur several times, notably during the Triassic and Jurassic. In the clade Synspermiata, we also found evidence of these eyes being regained!

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MultiplEye Lab @multipleye-lab.bsky.social · 13/05/2026

They surveyed eye number across ALL described spiders (yes, literally all), and report >7500 species that have lost one or more eye pairs. BUT not all eyes are lost equally - the vast majority of affected species lack the principal eyes, which are often associated with higher resolution vision...

Summary of eye losses in spiders. While most species have eight eyes, 11% of described diversity has fewer. Most affected species have lost the principal eyes only.

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MultiplEye Lab @multipleye-lab.bsky.social · 17/10/2025

🎉 Big news! 🎉 We will be moving to @bristolbiosci.bsky.social @bristoluni.bsky.social in 2026!! We're so excited to be joining such a dynamic and thriving department, university, and city - thank you to everyone who has already been so welcoming! 📢 But that's not all - come and join us! 👇

Atmospheric evening view of Bristol and the Clifton suspension bridge. Adobe Stock c Stephen Davies

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MultiplEye Lab @multipleye-lab.bsky.social · 11/07/2025

Fresh(ish) from the week at BESSY II @helmholtz.de looking at the changes associated with eye loss in spiders! Not pictured: our valiant night shifters, @mikebok.bsky.social, Karla Lopez Reyes, and Constance Coubris 💪🏼🌃

Three members of the group stand on a bridge over the ring at the BESSY II synchrotron

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MultiplEye Lab @multipleye-lab.bsky.social · 14/03/2025

Armed with data from the major clades, we can finally start to identify phylogenetic patterns of RDG expression! As ever, new questions spring up as we attempt to answer old ones, but hopefully this is one more step to understanding how spider eyes have achieved such diversity of form and function!

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MultiplEye Lab @multipleye-lab.bsky.social · 14/03/2025

Many of the retinal determination genes are present in duplicate, thanks to an ancient whole-genome duplication in arachnopulmonates. In the case of Six3, it appear that one copy is expressed at the centre of the secondary eyes, and the other surrounds it. Why? We don't know! But watch this space...

Colorimetric in situ of Six3 expression in Marpissa muscosa and Pardosa amentata embryos

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MultiplEye Lab @multipleye-lab.bsky.social · 14/03/2025

We also detected early gene expression in the principal eye primordia of Segestria senoculata, which *lack* AMEs and probably lost them 100s Ma...

Colorimetric in situ hybridisation of sine oculis expression in Segestria senoculata embryos

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MultiplEye Lab @multipleye-lab.bsky.social · 14/03/2025

Fun fact! The very small eye pair in salticids, historically called the posterior median eyes, in fact appears to be homologous to the posterior *lateral* eyes of other spiders! The salticid PMEs are dead, long live the salticid PMEs! (Cue lots of annoying nomenclature confusion, sorry)

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MultiplEye Lab @multipleye-lab.bsky.social · 14/03/2025

For example, extreme eye sizes are already established by stage 10-11 in salticids and lycosids, and the early division of the secondary eye primordium seems to contribute to their eventual positions on the cephalothorax, particularly the posterior lateral eyes. 3/n

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MultiplEye Lab @multipleye-lab.bsky.social · 14/03/2025

Although the retinal determination gene (RDG) repertoires are pretty conserved across the order, their spatial and temporal expression patterns provide clues about how important features such as eye size, function, and location might be determined, and how these have evolved over time 2/n

A phylogeny of seven spiders with their eye arrangements and retinal determination gene repertoires

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MultiplEye Lab @multipleye-lab.bsky.social · 16/02/2025

Thanks to the teams at the Soleil Anatomix and DISCO beamlines for hosting us and @sigwartae.bsky.social @oceanspecies.bsky.social this week! We learned lots of new tricks and are looking forward to working through the data together soon! There are always fun new ways to look at old chitons 💛

The multipleye and Sigwart labs at the Soleil synchrotron in Paris

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