Hair, Tooth or Scale?

Hair, Tooth or Scale? 

Although at first glance, these three appendages appear to have little in relation to one another, there are intriguing hints of a common developmental origin. Can you guess the identity of today’s Science Mystery Pix?

The Toothless Men of Sind: Our story begins in 1875, with Charles Darwin describing the curious case of a Hindu kindred whose males suffered a near absence of teeth and hair. This inherited condition, known as ectodermal dysplasia, was tracked down to defects in genes coding for a signaling protein (ectodysplasin-A or EDA) and its receptor (EDA receptor or EDAR). Similar hairless and toothless mutations were found in the mutant mouse strains Tabby and Downless, pointing to a common developmental origin for hair and teeth. 

Fighting Tooth and Scale : Which came first, teeth or scales? It is thought that the earliest teeth arose in shark-like fish that lived in the Early Devonian period, about 400 million years ago. The pointy tooth-like scales found near the mouth of fossils would have helped grasp prey or fight predators. Eventually, these transformed into the teeth of modern day mammals. 

A Fishy Tale: Now for the final link! Mutants of the medaka fish (Oryzias latipes), originally isolated from wild populations, are viable and fertile but completely lack scales. Named rs-3 (for reduced scale-3), the mutation affected the same ectodysplasin-A receptor (EDAR), which is required for the initiation of hair development in mammals. So what do you the image a 20x magnification of hair, tooth or scale?


Image from Dr. Havi Sarfaty of the Israel Veterinary Association and winner of Nikon Small World competition. 

  #ScienceSunday  #ISeeTheWorldWithScience  

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79 Responses to Hair, Tooth or Scale?

  1. Azlin Bloor says:

    I was born on the Ides of March, that might have helped to tip the balance. Too obscure, nomad dimitri? 

  2. Rajini Rao says:

    The color is a clue too, Azlin Bloor 🙂 Although, I’m not sure why the pigment is so patchy. 

  3. My guess was wrong, but you might want to consider renaming the file before you upload it 🙂

  4. Rajini Rao says:

    Haha! I’m not really trying to make this hard 🙂

    This is how I feel when I set questions for grad school exams 😉

  5. Azlin Bloor says:

    Akinola Emmanuel I shall resist looking! I went for the obvious because they look like … Mmm, obviously wrong. maria nasir any guesses?

  6. david olick says:

    I’m thinking hair. I’ve seen some close-up pictures of teeth before and they didn’t look like this. I am assuming the discoloration is pigmentation of the hair.

    However, I thought hair looked a bit different close up too, but I still think it looks more similar to hair 🙂

  7. Rajini Rao says:

    Thanks for all your guesses, folks! Who would have thought that the three have anything in common? david olick , hair does have overlapping layers, so that makes sense. 

  8. david olick says:

    Rajini Rao Oops! I completely missed the option of scale. I thought I had to choose between tooth and hair.

  9. Rajini Rao says:

    Rethinking your options, david olick ? 🙂

  10. maria nasir says:

    Rajini Rao, Azlin Bloor, though at first glance it looks like a beautiful watercolour painting of Chinese hand fans but my very, very wild guess is that these are scales, perhaps !

  11. Gary Ray R says:

    Another nice write up, Rajini Rao 

    Always read your fascinating posts.

    What kind of fish?  シ

  12. david olick says:

    Rajini Rao Yes, it definitely fits with a scale better lol

  13. Rajini Rao says:

    Chinese hand fan is a beautiful choice, maria nasir ! Gary Ray R , trying to trip me up, eh? 😀

  14. mary Zeman says:

    I see crochet pattern.  😛

  15. Rajini Rao says:

    mary Zeman , ooh very nice! Definitely lacy and handmade. Also reminds me of tatting which I learned when I was a little girl. It had these delicate bumps along edges.  

  16. Rugger Ducky says:

    I’m going with fish scales, but I think it looks like a lichen too.

  17. Rajini Rao says:

    Those little “floral” circles in the image do remind me of lichen growth on tough gray rocks, Rugger Ducky .

  18. Bill Collins says:

    Loved the image and the science. I will guess – completely just guess – that it’s scale.

  19. Rajini Rao says:

    Oh my Gosh! What a gorgeous photo, Rugger Ducky ! Thanks so much for sharing. 

    See those circles on the rock? They do look like the ones in this microscope image. 

  20. DaFreak says:

    Whether these are teeth, scales or hair, you can’t go wrong with keratin.

    I am going to wildly guess that this is a picture from an underwater dweller with such great aerodynamic properties that the ancient Olympians used them during their first games. (Yes, I cheated :p)

  21. Rajini Rao says:

    “Investigative Googling” sounds better, Koen De Paus 😉 Could you drop off a link re. the Olympics connection? I’m not finding it in my google search. 

  22. Wait a minute,Are you not advertising your hair?

  23. Rajini Rao says:

    Iniobong Akpan I have not experimented with orange hair yet 🙂

  24. DaFreak says:

    I should have said the ancient Olympians sort of used them although not really is closer. Yes I am being cryptic, I was afraid of making it too obvious.

    I am derailing your game towards guessing which animal the picture belongs to. :p

  25. Definitely scales, the colours remind me of Sparus aurata

  26. Rajini Rao says:

    Koen De Paus , the link is the most excellent clue! I like it 🙂

  27. Gary Ray R says:

    Great clue Koen De Paus, also native to the Amazon River basin. Thank you Wiki.

  28. Marta Rauch says:

    Great post, Rajini Rao. Fun to see the guesses and great collaboration.

  29. Rajini Rao says:

    Fun for me too, Marta Rauch . Hope you are having a relaxing weekend! 

  30. Gary Ray R says:

    Did you know you can drag and  drop images into google image search?  

    Cool feature that I have used before to identify strange unknown objects.

  31. Rajini Rao says:

    I do it all the time. Love the Image search on Google, Gary Ray R 🙂

  32. Gary Ray R says:

    I use the image search too Rajini Rao, we had found a sculpture of a bird in the backyard and I was able to identify it by taking a picture and doing  an image search.  I even found the artist, it was made in England.

    That what I did with your image.

    Learned it all from Search Guru Dan Russell  

  33. Rajini Rao says:

    The world is at our fingertips, Gary Ray R !

  34. DaFreak says:

    Many people forget but It truly is.

    I use this chrome extension; (pictured) which sort of makes you feel like an omniscient god at times. :p No more typing, everything you want to know is literally just one click away.

  35. Rajini Rao says:

    Just added it, Koen De Paus , thanks. I’ll let you know if my goddess quotient is elevated 🙂

  36. Gary Ray R says:

    The world of information, and the world of smart, engaging people.  One of the reasons that I like G+

  37. Mary T says:

    Guessing scales, but that might be too obvious :-).  Beautiful art work/photograph!

  38. Rajini Rao says:

    Sometimes the obvious is the right choice, Mara Rose  🙂 It looks like a delicate water color ..or even acrylic, because of the shine to it. 

  39. Mary T says:

    So much beautiful art in Nature, Rajini Rao and you find marvelous examples.

  40. Rajini Rao says:

    Answer: for those who had not already cheated guessed : these are the scales of a discus fish, magnified 20 times. It won 6th prize in the Nikon Small World photo competition in 2009.

  41. Stuti S A I says:

    Hair: They are more in number and relatively more spread out throughout the body;

    Teeth: Localised with a different composition;

    Scales: Similar to hair but more “fleshy”.

    Apparently, the threesome should have different and unique origin in terms of their “biological/morphological” coding. But, if you compare the human evolution from an ape to a man vis-a-vis the body-appendages’ origin from scales->hair-> teeth or any other order, things appear more cloudy!!!!

  42. Lo Sauer says:

    Amazing Rajini Rao. A wonderful summary as always 🙂 Do you know if EDAR expressed on other tissue / cell-types as well?

  43. Rajini Rao says:

    Hi Lo Sauer , the EDA/EDAR signaling system works on all epidermal outgrowths: hair follicles, sweat and oil glands, mammary glands, teeth and many others. Also, they are not expressed all the time but are turned on in response to other developmental signals (anagens). 

  44. Rajini Rao says:

    Clyde Herrington , the answer and link are a few comments up. The image is of ordinary fish scales 🙂

  45. Rajini Rao the common thing between hair & scale is keratin, i think.  i know that the hard substance that covers teeth is some kind of dentin or adamantin, if i remember correctly.  i assume that tooth is an extension of bone, therefore calcium and all that.  so i am stumped on the common origins of the 3.  surprised.

    the photo: i would say hair, or fur?

  46. Rajini Rao says:

    nomad dimitri interestingly, while reptile scales have keratin, as do mammalian hair, hooves, horns, and bird feathers, the scales in fish (which is what this image shows in 20x magnification) are different- made of bony dentine like material. In fact, the placoid scales of sharks are closely related to teeth. 

  47. Rajini Rao fascinating.  servers me right, i thought scales, of course, and then i thought it was a trick question.  got you with the woodpecker though!!!

  48. Rajini Rao says:

    nomad dimitri , let the second round of competition begin! FYI, I thought the burrow was that of the burrowing owl..hence the allusion to being wise. 

  49. Rajini Rao oh, i got the allusion, it was the best guess so far.  in california the burrow in the ground, like mice, it is unbelievable!

  50. Definitely the scales. 🙂

  51. Rajini Rao says:

    Brian Mahon , definitely scales! But not placoid. Those are found in sharks and look pointy and toothlike. These are from a discus fish, so probably ctenoid, because of their edges. 

  52. Rajini Rao don’t forget about this week’s post ;)))

  53. Rajini Rao says:

    Susana M. I have a Valentine’s Day poem/science post for you. My husband said it was boring 😦 

    We’ll have to prove him wrong, haha. 

  54. Perfect for the occasion!

    Ha!! Of course he’s wrong 😉

  55. Bill Collins says:

    Well what does he have to say on it??


  56. Rajini Rao says:

    Bill Collins this is the guy who watched me practice my thesis defense many years ago, interrupting me with this helpful suggestion: why don’t you walk from one end of the stage to the other , you know, just to wake people up” 😀

  57. Scales on teeth, showing plaque deposits


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  59. I would guess scale.

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