Uploaded November 2025 | Updated September 2026, 1 hour ago
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The Mexican tetra, lives in freshwater streams and pools from Mexico up into the southern United States. But these fish also live in cave systems in at least 29 separate places in Mexico, where they have no pigment, and anywhere from minimal eye function to virtually no eyes at all.
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#BizarreBeasts #caves #cavefish
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Sources:
science.org/doi/10.1126/science.ady4515
nps.gov/cabr/blogs/excuse-me-what-do-you-keep-in-your-gular-pouch.htm
discoverwildlife.com/animal-facts/mammals/why-do-aye-ayes-have-such-weird-hands
nature.com/articles/6884120
livescience.com/18069-evolution-blind-cavefish-image-gallery.html
https://www.fishbase.se/summary/astyanax-mexicanus.html
nanfa.org/articles/acastya.shtml
https://www.fishbase.se/Nomenclature/2740
https://aquadiction.world/species-spotlight/mexican-tetra/
bmcecolevol.biomedcentral.com/articles/10.1186/s12862-018-1156-7
denverzoo.org/animals/blind-cave-fish
doi.org/10.1242/jeb.208835
sciencedirect.com/science/article/pii/S2589004222000487
onlinelibrary.wiley.com/doi/full/10.1111/mec.17128
livescience.com/18069-evolution-blind-cavefish-image-gallery.html
nature.com/articles/s41467-020-16497-x
bmcecolevol.biomedcentral.com/articles/10.1186/1471-2148-12-9
evodevojournal.biomedcentral.com/articles/10.1186/2041-9139-4-26
science.org/doi/10.1126/sciadv.1500363
sciencedirect.com/science/article/pii/S0960982207008901
https://evolution.berkeley.edu/evolution-101/mechanisms-the-processes-of-evolution/genetic-drift/
cell.com/trends/genetics/abstract/S0168-9525(23)00230-5
livescience.com/regressive-backward-evolution
mpi-cbg.de/news-outreach/news-media/article/regressive-evolution-limb-loss-in-snakes-and-degeneration-of-eyes-in-subterranean-mammals
pmc.ncbi.nlm.nih.gov/articles/PMC8017920
nature.com/articles/s41467-023-37909-8
science.org/doi/10.1126/science.1240276
sciencedirect.com/science/article/pii/S0960982207022622#bib4
https://www.science.org.au/curious/earth-environment/why-evolution-isnt-perfect
pmc.ncbi.nlm.nih.gov/articles/PMC7328453
science.org/doi/10.1126/science.aal3345
journals.biologists.com/jeb/article/223/Suppl_1/jeb208835/224588/Utilizing-the-blind-cavefish-Astyanax-mexicanus-to
science.org/doi/abs/10.1126/science.289.5479.631
------
Images:
docs.google.com/document/d/1O1FBe1I6xGiA_Gcuh8ZPFOXi_ecdQNblqzEhWUTWp0w/edit?usp=sharing
Get exclusive NordVPN deal here: NordVPN.com/bizarrebeasts It’s risk free with Nord’s 30 day money-back guarantee!
The Mexican tetra, lives in freshwater streams and pools from Mexico up into the southern United States. But these fish also live in cave systems in at least 29 separate places in Mexico, where they have no pigment, and anywhere from minimal eye function to virtually no eyes at all.
Find out more about the National Geographic Photo Ark here: joelsartore.com
youtube.com/@PhotoArk
Subscribe to the pin club here: https://complexly.store/products/bizarre-beasts-pin-subscription
This month's pin is designed by Charlotte Gomez. You can find out more about her and her work here: charlotte-gomez.com
You can cancel any time by emailing hello@dftba.com
Follow us on socials:
Instagram: instagram.com/bizarrebeastsshow
Facebook: facebook.com/BizarreBeastsShow
Bluesky: https://bsky.app/profile/bizarrebeastsshow.bsky.social
#BizarreBeasts #caves #cavefish
-----
Sources:
science.org/doi/10.1126/science.ady4515
nps.gov/cabr/blogs/excuse-me-what-do-you-keep-in-your-gular-pouch.htm
discoverwildlife.com/animal-facts/mammals/why-do-aye-ayes-have-such-weird-hands
nature.com/articles/6884120
livescience.com/18069-evolution-blind-cavefish-image-gallery.html
https://www.fishbase.se/summary/astyanax-mexicanus.html
nanfa.org/articles/acastya.shtml
https://www.fishbase.se/Nomenclature/2740
https://aquadiction.world/species-spotlight/mexican-tetra/
bmcecolevol.biomedcentral.com/articles/10.1186/s12862-018-1156-7
denverzoo.org/animals/blind-cave-fish
doi.org/10.1242/jeb.208835
sciencedirect.com/science/article/pii/S2589004222000487
onlinelibrary.wiley.com/doi/full/10.1111/mec.17128
livescience.com/18069-evolution-blind-cavefish-image-gallery.html
nature.com/articles/s41467-020-16497-x
bmcecolevol.biomedcentral.com/articles/10.1186/1471-2148-12-9
evodevojournal.biomedcentral.com/articles/10.1186/2041-9139-4-26
science.org/doi/10.1126/sciadv.1500363
sciencedirect.com/science/article/pii/S0960982207008901
https://evolution.berkeley.edu/evolution-101/mechanisms-the-processes-of-evolution/genetic-drift/
cell.com/trends/genetics/abstract/S0168-9525(23)00230-5
livescience.com/regressive-backward-evolution
mpi-cbg.de/news-outreach/news-media/article/regressive-evolution-limb-loss-in-snakes-and-degeneration-of-eyes-in-subterranean-mammals
pmc.ncbi.nlm.nih.gov/articles/PMC8017920
nature.com/articles/s41467-023-37909-8
science.org/doi/10.1126/science.1240276
sciencedirect.com/science/article/pii/S0960982207022622#bib4
https://www.science.org.au/curious/earth-environment/why-evolution-isnt-perfect
pmc.ncbi.nlm.nih.gov/articles/PMC7328453
science.org/doi/10.1126/science.aal3345
journals.biologists.com/jeb/article/223/Suppl_1/jeb208835/224588/Utilizing-the-blind-cavefish-Astyanax-mexicanus-to
science.org/doi/abs/10.1126/science.289.5479.631
------
Images:
docs.google.com/document/d/1O1FBe1I6xGiA_Gcuh8ZPFOXi_ecdQNblqzEhWUTWp0w/edit?usp=sharing
