I have a large insectoid creature with compound eyes in my story. The creature’s habitat is prone to sudden dust storms; as a result, I was planning to have it evolve a set of eyelids so it could protect its delicate eyes from particles. Is it feasible for a creature with an exoskeleton and compound eyes to have a set of eyelids? No arthropod on Earth has eyelids (as far as I’m aware) so they may not be necessary or possible, but they would be nice to have for making the creature more visually expressive.
$\begingroup$
$\endgroup$
4
-
2$\begingroup$ Ahh no.. imagine, as a human, being in a place where pebbles sized 2-4cm would fly around for hours at high speeds.. You'd need more to protect than just your eyes ! Insects will dig into the ground deep to be safe, before a sand storm arrives, eyelids would not suffice to protect the animal. $\endgroup$– GoodiesDec 18, 2021 at 12:03
-
2$\begingroup$ You could also go the cool route: Regeneration. Ogre spiders have incredibly sensitive eyes that burn away each dawn from exposure to sunlight. Fortunately, they also have the capability to rapidly regrow the destroyed portion. $\endgroup$– JafegoDec 18, 2021 at 14:02
-
$\begingroup$ How large are your creatures? $\endgroup$– AlexPDec 18, 2021 at 20:43
-
$\begingroup$ @AlexP The creatures are approximately human-sized. Obviously this presents more physics problems than just eyes but I plan to deal with those separately. $\endgroup$– Mark PriceDec 19, 2021 at 0:51
Add a comment
|
2 Answers
$\begingroup$
$\endgroup$
7
I don't think eyelids are needed for insect eyes: you are probably familiar with the image of an insect washing itself, eyes included, by rubbing it with its fore limbs.
I am pretty sure that if I was to rub my eye's bare surface with my hands it would be all but pleasant. The evidence that they do this on a constant base for several generations suggests that the compound insect eyes are more sturdy than the vertebrate eye.
Moreover, insects do live already in very dusty environments, and none of them has evolved eyelid, meaning their absence is not a game killer.
-
4$\begingroup$ +1 agree with this one.. I would add: insect eyes are less vulnerable because the retina is on the outside. It has to be kept clean, but they don't have an eye lens and the accompanying vulnerable construct, involving a thin cornea up front and eye fluid, inside. Of course, insects also pay for their simpler eye: they will see no colors, and less contrast. Also, part of their brain needs to be sticking out, making the brain less protected. $\endgroup$– GoodiesDec 18, 2021 at 11:56
-
$\begingroup$ @Goodies Good info about compound eye structure. As a nitpicker, I would like to add that insects can see color, although it varies by type and the cones they possess are frequently very different than what humans have. Most flies have fewer cone types than humans, bees are tied with humans at three, but some butterflies may have as many as five. Although it is also true that due to their much smaller brains, their ability to process the information from their senses is also decreased. $\endgroup$– JafegoDec 18, 2021 at 14:00
-
$\begingroup$ Ah interesting.. didn't know insects have the tools for colors. The segments of its eye are separated and linked to one brain entry, Using the compound eye, mammals can mix colors, by directing the light from the same spot, to specialized cones. When insects have "green segments", "red segments" etc it would be like color TV (near pixels of primary color), or a sort of "Van Gogh" like color perception... $\endgroup$– GoodiesDec 18, 2021 at 15:42
-
$\begingroup$ @Goodies: The "retina" is most definitely not on the outside; and the elements of the compound eye do have lenses. First, there is no retina as such. Second, the photoreceptor cells are not on the outside. Here is the structure of an ommatidium. (The elements of which a compound eye is made of are called ommatidia, singular ommatidium.) The outer surface of a compound eye element is a transparent cornea; the difference is that in land arthropods the cornea is dry (not moist as in vertebrates) and rigid (not flexible as in vertebrates). $\endgroup$– AlexPDec 19, 2021 at 1:18
-
$\begingroup$ @AlexP you're right.. each eye facet has a little lens (cornea) on top. But the light-sensitive tissue and the retina are underneath that. In a mammal eye, there is at least 15-20mm distance between the outside and the retina, and the retina safely inside, connected to the brain on the inside. $\endgroup$– GoodiesDec 19, 2021 at 1:24
$\begingroup$
$\endgroup$
3
As a slight frame-challenge:
An alternative possibility is to have the eyes on moving stalks which allows the animal to "flip" them under protective coverings.
Being on the "head" and near the mouthparts would allow for a moist lick to clear the external lens-cover as per this inspirational video of a crab cleaning it's eyes.
answered Dec 18, 2021 at 9:20
-
2$\begingroup$ Some snails have eyes on stalks too. I wonder if this can work for insects. Do they have the room for it ? In the case of retractable stalks, the brain tissue involved has to be flexible and light weight, muscles are needed around the stem of the stalk for the retract. I wonder if it would be an easy design for insects, with little room to retract eyes into.. it may be easier to retract the head ? the turtle method ? $\endgroup$– GoodiesDec 18, 2021 at 16:05
-
$\begingroup$ @Goodies if the eyes could retract into their socket on short stalks, could there feasibly be some sort of cleaning membrane that folds over them while they are retracted? I could change the head structure/brain cavity to accommodate for this, as the creature’s insect likeness is somewhat loose. I’m mostly looking for an excuse for the visual likeness to eyelids, which this would be similar to. The creature is approximately human-sized, so scale of dust particles could be less of an issue. $\endgroup$ Dec 19, 2021 at 1:00
-
$\begingroup$ Aha well.. if it is human sized, with a large brain and requiring advanced eyes, it may be a better idea to put eyelids. Eyes on stalks are a primitive construct, they provide limited retina size and no fixed reference for a 3d view. It would require the brains to adjust binocular input for relative position of the stalks. Eyelids would look somewhat exotic on an insect-shaped creature, but nothing inhibits a large creature to develop eyelids.. $\endgroup$– GoodiesDec 19, 2021 at 1:16