# Most successful animal -- with no eyes? **URL:** \ **Category:** Factual Questions\ **Created:** [September 4, 2012, 6:55pm UTC](https://boards.straightdope.com/t/most-successful-animal-with-no-eyes/633666 "2012-09-04T18:55:38Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![The\_Controvert](https://avatars.discourse-cdn.com/v4/letter/t/dec6dc/32.png) [@The\_Controvert](https://boards.straightdope.com/u/The_Controvert)\ **Post date:** [September 4, 2012, 6:55pm UTC](https://boards.straightdope.com/t/most-successful-animal-with-no-eyes/633666/1 "2012-09-04T18:55:38Z")
What is the most successful animal species that doesn’t possess eyes? I suppose folks will quibble over the definition of “successful” and “eyes”. Define success by your own criteria. Eyes are sensory organs that perceive objects. So I would say compound eyes and eye cups and spider’s eyes are eyes. A light-sensitive cell is not an eye because it doesn’t know what direction the light comes from. ---
**Author:** ![Lust4Life](https://avatars.discourse-cdn.com/v4/letter/l/ecc23a/32.png) [@Lust4Life](https://boards.straightdope.com/u/Lust4Life)\ **Post date:** [September 4, 2012, 7:00pm UTC](https://boards.straightdope.com/t/most-successful-animal-with-no-eyes/633666/2 "2012-09-04T19:00:01Z")
Aren’t there some deep ocean animals living near “smokers”, (volcanic vents) which are pretty successful, Hagworms and a kind of shrinp for example). Plus trogladytic animals/insects in deep cave systems. ---
**Author:** ![Smeghead](https://avatars.discourse-cdn.com/v4/letter/s/f1d935/32.png) [@Smeghead](https://boards.straightdope.com/u/Smeghead)\ **Post date:** [September 4, 2012, 7:18pm UTC](https://boards.straightdope.com/t/most-successful-animal-with-no-eyes/633666/3 "2012-09-04T19:18:48Z")
Do nematodes count as animals? They’re in the animal kingdom. I don’t know which species is most common, but that’s what I’d put my money on. ---
**Author:** ![AndrewL](https://avatars.discourse-cdn.com/v4/letter/a/3d9bf3/32.png) [@AndrewL](https://boards.straightdope.com/u/AndrewL)\ **Post date:** [September 4, 2012, 7:18pm UTC](https://boards.straightdope.com/t/most-successful-animal-with-no-eyes/633666/4 "2012-09-04T19:18:56Z")
Earthworms? I’d suggest bacteria, but I suspect that might not count as an animal. ---
**Author:** ![TriPolar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripolar/32/3008_2.png) [@TriPolar](https://boards.straightdope.com/u/TriPolar)\ **Post date:** [September 4, 2012, 7:52pm UTC](https://boards.straightdope.com/t/most-successful-animal-with-no-eyes/633666/5 "2012-09-04T19:52:17Z")
Kind of hard to figure successful in this. Everything more developed than a worm is stuck in a dark niche environment right? ---
**Author:** ![Sailboat](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/sailboat/32/461_2.png) [@Sailboat](https://boards.straightdope.com/u/Sailboat)\ **Post date:** [September 4, 2012, 7:58pm UTC](https://boards.straightdope.com/t/most-successful-animal-with-no-eyes/633666/6 "2012-09-04T19:58:26Z")
Termites might be what you’re looking…err…groping around for. Although some castes do have working eyes. ---
**Author:** ![kyogi](https://avatars.discourse-cdn.com/v4/letter/k/51bf81/32.png) [@kyogi](https://boards.straightdope.com/u/kyogi)\ **Post date:** [September 4, 2012, 8:00pm UTC](https://boards.straightdope.com/t/most-successful-animal-with-no-eyes/633666/7 "2012-09-04T20:00:52Z")
Mussels? ---
**Author:** ![TriPolar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripolar/32/3008_2.png) [@TriPolar](https://boards.straightdope.com/u/TriPolar)\ **Post date:** [September 4, 2012, 8:12pm UTC](https://boards.straightdope.com/t/most-successful-animal-with-no-eyes/633666/8 "2012-09-04T20:12:00Z")
> [@TriPolar](#): > > Kind of hard to figure successful in this. Everything more developed than a worm is stuck in a dark niche environment right? I guess ‘worm’ may be too simple for my point. I didn’t consider termites, which are pretty successful considering the ecology for all land animals would be quite different without them or some other animal in their role. Mussel varieties are found all over the place in both fresh and salt water, though they must be pretty diverse species. But I can’t think of a reptile, bird, or mammal that could be called successful without eyes. I can’t even think of a bird without eyes at all. I’ll bet Colibri would know if there was one. ---
**Author:** ![John\_Mace](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/john_mace/32/185_2.png) [@John\_Mace](https://boards.straightdope.com/u/John_Mace)\ **Post date:** [September 4, 2012, 8:21pm UTC](https://boards.straightdope.com/t/most-successful-animal-with-no-eyes/633666/9 "2012-09-04T20:21:28Z")
> [@AndrewL](#): > > I’d suggest bacteria, but I suspect that might not count as an animal. It’s going to be some sort of single celled organism in the Animal Kingdom. They will outnumber any multi-celled thing by orders of magnitude. ---
**Author:** ![Skammer](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/skammer/32/143_2.png) [@Skammer](https://boards.straightdope.com/u/Skammer)\ **Post date:** [September 4, 2012, 8:29pm UTC](https://boards.straightdope.com/t/most-successful-animal-with-no-eyes/633666/10 "2012-09-04T20:29:06Z")
In addition to living in dark caves, blind cave fish are also commonly found in aquariums. So they’ve spread far beyond their native environment! ---
**Author:** ![Lukeinva](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lukeinva/32/17872_2.png) [@Lukeinva](https://boards.straightdope.com/u/Lukeinva)\ **Post date:** [September 4, 2012, 8:35pm UTC](https://boards.straightdope.com/t/most-successful-animal-with-no-eyes/633666/11 "2012-09-04T20:35:27Z")
Worms are successful because they can dig, and they can come up for air when it is raining and they catch fish. Trifecta. ---
**Author:** ![dracoi](https://avatars.discourse-cdn.com/v4/letter/d/90db22/32.png) [@dracoi](https://boards.straightdope.com/u/dracoi)\ **Post date:** [September 4, 2012, 8:37pm UTC](https://boards.straightdope.com/t/most-successful-animal-with-no-eyes/633666/12 "2012-09-04T20:37:28Z")
I’m going with some kind of sedentary aquatic life form - coral, probably, but sponges, anemones, tube worms, etc. should also be in the running. I know that the bulk of material in a coral reef is technically dead, but there’s a lot of living material on the surface, and coral survives across a large portion of the world’s surface and has done so for long period of time. ---
**Author:** ![lazybratsche](https://avatars.discourse-cdn.com/v4/letter/l/ba8739/32.png) [@lazybratsche](https://boards.straightdope.com/u/lazybratsche)\ **Post date:** [September 4, 2012, 8:55pm UTC](https://boards.straightdope.com/t/most-successful-animal-with-no-eyes/633666/13 "2012-09-04T20:55:06Z")
Maybe something planktonic? Hell of a lot of microscopic animal biomass there. Though after [del]browsing wiki for five minutes[/del] extensive research, it appears that most of those arthropods have eyes. Rotifers, too, have extremely simple eyes, though most of those are closer to light detecting cells. Hydra don’t have eyes, though other cnidarians do have “eye spots” which probably don’t meet the OP’s criteria for an eye. ---
**Author:** ![njtt](https://avatars.discourse-cdn.com/v4/letter/n/ecd19e/32.png) [@njtt](https://boards.straightdope.com/u/njtt)\ **Post date:** [September 4, 2012, 8:55pm UTC](https://boards.straightdope.com/t/most-successful-animal-with-no-eyes/633666/14 "2012-09-04T20:55:15Z")
> [@The\_Controvert](#): > > A light-sensitive cell is not an eye because it doesn’t know what direction the light comes from. [That is not really true.](http://www.nature.com/nature/journal/v456/n7220/full/nature07590.html) Animals with eyes consisting of a single light sensitive cell, do indeed use them to sense the direction of light, and guide themselves towards it. Indeed, I don’t think the cells are used for much, if anything, else. In terms of the numbers of such organisms, they are very successful too. As for the actual answer to your question, no idea. 😉 ---
**Author:** ![Elendil\_s\_Heir](https://avatars.discourse-cdn.com/v4/letter/e/7cd45c/32.png) [@Elendil\_s\_Heir](https://boards.straightdope.com/u/Elendil_s_Heir)\ **Post date:** [September 4, 2012, 10:26pm UTC](https://boards.straightdope.com/t/most-successful-animal-with-no-eyes/633666/15 "2012-09-04T22:26:32Z")
> [@Smeghead](#): > > Do nematodes count as animals? They’re in the animal kingdom. I don’t know which species is most common, but that’s what I’d put my money on. Yup. They appeared on the very first episode of _SpongeBob_. That sounds pretty successful to me. ---
**Author:** ![Tamerlane](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tamerlane/32/7602_2.png) [@Tamerlane](https://boards.straightdope.com/u/Tamerlane)\ **Post date:** [September 4, 2012, 11:17pm UTC](https://boards.straightdope.com/t/most-successful-animal-with-no-eyes/633666/16 "2012-09-04T23:17:50Z")
Not the winner overall, but among the **vertebrates** I’d venture the [Brahminy Blind Snake](http://en.wikipedia.org/wiki/Ramphotyphlops_braminus) is tops. ---
**Author:** ![dracoi](https://avatars.discourse-cdn.com/v4/letter/d/90db22/32.png) [@dracoi](https://boards.straightdope.com/u/dracoi)\ **Post date:** [September 4, 2012, 11:51pm UTC](https://boards.straightdope.com/t/most-successful-animal-with-no-eyes/633666/17 "2012-09-04T23:51:57Z")
> [@Tamerlane](#): > > Not the winner overall, but among the **vertebrates** I’d venture the [Brahminy Blind Snake](http://en.wikipedia.org/wiki/Ramphotyphlops_braminus) is tops. But Wikipedia says: > [@](#): > > The tiny eyes are covered with translucent scales, rendering these snakes almost entirely blind. The eyes cannot form images, but are still capable of registering light intensity. ---
**Author:** ![Senegoid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/senegoid/32/6606_2.png) [@Senegoid](https://boards.straightdope.com/u/Senegoid)\ **Post date:** [September 5, 2012, 2:57am UTC](https://boards.straightdope.com/t/most-successful-animal-with-no-eyes/633666/18 "2012-09-05T02:57:39Z")
River dolphins – kinda, sorta, maybe. They have made their niche living in muddy rivers, and their eyes have devolved into little more than vestigial remnants. They lack a crystalline lens, and are commonly described as being blind – although it’s not entirely clear if they are totally blind, or if they can see vague unfocused light. Example: [South-East Asian River Dolphin](http://en.wikipedia.org/wiki/South_Asian_river_dolphin). Other species exist in the Indus River and Amazon River, I believe. ---
**Author:** ![Beware\_of\_Doug](https://avatars.discourse-cdn.com/v4/letter/b/278dde/32.png) [@Beware\_of\_Doug](https://boards.straightdope.com/u/Beware_of_Doug)\ **Post date:** [September 5, 2012, 3:43am UTC](https://boards.straightdope.com/t/most-successful-animal-with-no-eyes/633666/19 "2012-09-05T03:43:16Z")
> [@Skammer](#): > > In addition to living in dark caves, blind cave fish are also commonly found in aquariums. So they’ve spread far beyond their native environment! You spelled [fsh](https://i.chzbgr.com/completestore/12/6/16/zSm35hzDqkav7exPkFggIQ2.jpg) wrong. ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [September 5, 2012, 3:49am UTC](https://boards.straightdope.com/t/most-successful-animal-with-no-eyes/633666/20 "2012-09-05T03:49:37Z")
> [@John\_Mace](#): > > It’s going to be some sort of single celled organism in the Animal Kingdom. They will outnumber any multi-celled thing by orders of magnitude. Technically, there aren’t any single celled organisms in the Kingdom Animalia under modern classifications. The Protozoa (single celled Eucaryotes) are generally classified as the Kingdom Protista (or according to some Protoctista) these days. (However, according to a cladistic classification, the Protozoa themselves are polyphyletic and would contain a dozen or more clades equivalent to Kingdom rank.) Within the Animalia, I would probably go with nematodes as a group. They are extremely abundant, and they are almost everywhere. I’ve heard it said that if everything but nematodes disappeared, you would still see the ghostly shapes of the soil, trees, animals, plants, and people outlined in the nematodes they contained. [Next page](https://boards.straightdope.com/t/most-successful-animal-with-no-eyes/633666.md?page=2)