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In one question I asked how insects can evolve their base biology to grow in size here.

Which was followed up by this question about how well the antennae would fare when increased in size here

Now I'm trying to figure out how the eyes would evolve. At their current size now, the compound eyes serve insects just fine. However, the low quality of the image combined with how the lenses go along with rest of the exoskeleton would not translate well with an increase of size where insects may stop shedding and would very likely need a to see in clearer definition in order to survive.

What adaptations do eyes have to go through when size increases?

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  • $\begingroup$ Would shedding change as an insect grew larger? Might a multi-eyed insect start shedding in parts, allowing, say, two of six eyes to always be functional? Just a thought. $\endgroup$ – DWKraus May 21 at 13:11
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Compartmentalization of the Eye, then Extreme Specialization within each Compartment.

Let's talk about human eyes for a moment here. Humans use one type of eye to do everything. Technically, yes, we have two eyes, but from a biological perspective, they're more or less identical in function, and they only operate in a pair to give humans depth perceptions. Because of this, the human eye is designed to be super versatile. It has a lenses which can adjust itself to focus between objects which are closer or farther away. It also lies within an occipital socket that allows the eye to move and focus on various things within it's field of vision. Note that the occipital socket doesn't actually give you a larger field of vision (a marginal improvement at best), just the ability to focus on details at any range. In other words, since humans have only had one type of eye to use, the eye can do everything. This however, comes with a drawback - jack of all trades, master of none. Trade-offs exist, and since the human eye is designed to be able to do everything, it can't do everything as well as an eye specialized for the task can. It also usually comes with a defect of some kind in certain areas, which is why most people wear some type of correctional lenses or another, i.e. glasses or contact lenses.

Various other types of animals have eyes which are specialized for certain tasks, but are absolutely useless when it comes to others. 'Eagle eyes' are a good example here - they cannot rotate their eyes, they're not so good at seeing color (even though they can see more colors than humans can), and they have a blind spot directly in front of them. Not something that I'd ever actually want.

However, the insect's unique compound eyes present a way to get everything, and that's by having patches of the eye each be uniquely adapted to whatever the insects needs. In fact, this already occurs among some insects, like superior flier such as dragonflies, where they have specialized section for acute vision. Essentially, each part of the compound eye would be claimed by whatever part needed it the most. It would have a section devoted to long distance acute vision to spot things far away, and a section devoted to seeing things up close to avoid the blindspot. (Kind of like bifocal glasses, funnily enough.) Most of what it would see would actually be in grayscale, given that seeing in color would take up precious space in the eye, but sections of it would evolve to pick out and see colors with precision, possibly even a greater range than we humans have. The eyes on the extreme edge would be made not for accuracy, but rather for extreme angles so they could see as far around themselves as possible.

The one thing I'm not sure about is whether or their eyes could move. It's possible that they would eventually develop an occipital socket to move their eye around, but it's more likely that with how complex their eyes become, they wouldn't be able to move them and would need to turn their whole head to see things with the relevant part of their eyes.

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    $\begingroup$ Notably, this kind of specialization is already well-developed in spiders, whose multiple pairs of eyes tend to be specialized for wildly different purposes. $\endgroup$ – Logan R. Kearsley May 21 at 18:59
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Super-resolution: I would agree that the compound eyes could be looked at much like digital cameras. Simulated digital compound eyes are already being developed and the design details for larger ones with increased resolution are in the works https://www.nature.com/news/digital-camera-gives-a-bug-s-eye-view-1.12914 Some of these are anticipated to have high resolution https://www.cnn.com/2013/05/01/tech/innovation/bug-eye-camera/index.html For that matter, why can't the simple images of compound eyes get processed by an increasingly complex neural process so the compound image is spliced-and-diced like a multitude of digital images to produce a higher resolution composite image?https://petapixel.com/2015/02/21/a-practical-guide-to-creating-superresolution-photos-with-photoshop/ Bigger bugs mean bigger brains. For cameras this currently calls for relatively still objects, but the technology is evolving, and so would the processing of the eye data. Organisms could even take advantage of the motion to accurately track movement and velocity. different compound eye shapes give better distance vision, movement tracking, depth perception, etc. and you could have multiple compound eyes each performing a different specialized task as needed. Engineers are trying their best not to make these cameras much bigger but instead making them so the cameras can be smaller but still do the jobs of bigger cameras. I can't speak to the shedding part, but evolution does amazing things with developing new materials.

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The obvious way for insect eyes to evolve parallels the development of the CCD and CMOS image sensors used in digital imaging. Rather than try to evolve a vertebrate-like eye, evolution just increases the number of pixels in the compound eye.

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  • $\begingroup$ I'm giving this one props, I wouldn't have thought of my answer without this as a starting point. Thanks! $\endgroup$ – DWKraus May 21 at 4:18
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I think convergent evolution is likely to bring the compound eye of insects to become something similar to what vertebrates have as eye.

At the very end, sharks and dolphins have similar body shapes to solve the same problem, thus it is reasonable that also this other problem will be solved with the same approach.

Thus the adaptions will be:

  • single optical chamber
  • single lens
  • iris
  • extended photosensitive layer
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  • $\begingroup$ Really? I thought that the massive difference’s between the two eye structures would prevent such an occurrence. That and both dolphins and sharks technically have a common ancestor which had the usual light pit for an eye while insects had compound eyes through and through for the past few eons. Fossil record would neat to look at thought. $\endgroup$ – Seraphim May 18 at 6:22
  • $\begingroup$ @Seraphim, if an insect-like body plan is going through a massive rework to grow in size, why shouldn't the eye be affected? $\endgroup$ – L.Dutch - Reinstate Monica May 18 at 6:25
  • $\begingroup$ I know that the eyes would be affected, I just wasn’t sure how they would be affected. Compound eyes that have the lenses and out of the eye and each having a separate light receptor would seem odd to evolve eyes like are own. Though if the internal structure is different, than maybe not. $\endgroup$ – Seraphim May 18 at 6:28
  • $\begingroup$ @Seraphin have you ever heard about the octopus' eyes? Not only they're incredibly similar to ours, they have no blind spot whatsoever, that is due to them evolving from invaginations in their skin rather than as an extension of the nervous system, causing the nerves to be pointing the opposite direction, thus not requiring a hole in the eyeball to come out of it. If an octopus can develop eyes extremely similar to ours through their skin, it's far from a stretch that insects could also suffer great changes in their eyes to adapt to their size $\endgroup$ – ProjectApex May 18 at 10:49
  • $\begingroup$ No. You have a "can't get there from here" problem. Shark & dolphin eyes (and all other vertebrate eyes) are just variations on the eye of a common ancestor. (And cephalopod eyes, though in many ways similar, are the product of a separate evolution.) The compound eyes of insects are fundamentally different. $\endgroup$ – jamesqf May 18 at 17:16
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Quite contraordianry, but insects are far more advanced than mammals or fishes in terms of number of evolutional changes from common ancestor of all bileteral chord animals (yes insects have sort-of hord - they just left this obsolete feature behind). It means that their eyes are not a "ancient sidebranch" to our eyes, but one of ways of their development.

So to have eyes like ours insects need to "deevolve" them to more simple state ("on-facet eye") and then reevlove to "animal eye". This seems quite unprobable.

But still something like this is possible and some insects are on this way right now. You see - one facet (or group of facets) of an eye can become bigger and more complex, resembling sort-of "normal eye".

This leads to quite bizzare endstate: ether one large (non-movable ?) eye or multu-eye (say with 7 "sub-eyes" in hexagone pattern ) with good resolution each - playes same role as macule and a lot of smaller and more simple facets around - for low light vision and fast movement resolution. The true trypophobia nightmare fuel!

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