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New discoveries, right under your nose

Just when you think there are no surprises left in our animal-centered corner of the realm of biology, there certainly are some! Sometimes these are amazing—if not always visually spectacular—new species discovered in some remote part of the world, or some unfathomably odd behavior or reproductive mode. And sometimes the discoveries are right under our noses, and I mean that literally.

Recently, some medical researchers had a story break in The New York Times and elsewhere about their apparent discovery of a pair of previously unknown salivary glands deep in the skull, directly behind our noses. To the researchers’ credit, these things are in a difficult place to examine either through dissection or modern imaging techniques. This is why, presumably, simply nobody had noticed them before. How exciting! See link at the end here. It will be interesting to follow this story over the next few years to learn what these things actually do in our bodies. One certainly does not expect there to be any surprises left in basic human anatomy left after so many centuries of intense study.

I had a similar experience in grad school, many years ago, except our findings were not featured in The New York Times. Frogs have always been model organisms for studying and learning the basics of vertebrate anatomy. Many of us will remember dissecting leopard frogs in high school biology classes, a tradition that thankfully is waning in popularity in lieu of online demonstrations. So, perhaps second only to humans, frogs would seem to be a last place where anatomical surprises laid undiscovered.

One evening in grad school, a fellow student and I were dissecting specimens of a common South American toad species. We were interested in some obscure anatomical features in the shoulder girdle and breastbone and this toad seemed like a good candidate for study. My friend, at one point, noticed a pair of conspicuous organs nestled at the bottom of the toad’s internal cavity, nestled between the skin and musculature of the leg and body wall. These things were obvious, looking like little Raisinets candies at the internal base of each leg. We stared at each other in disbelief—neither of us had ever noticed such organs in any species of frog or toad. How could we possibly not know about these things? Frog anatomy is what we were specializing in, and our lab was full of the very best and up-and-coming frog anatomists in the world. Believing that such conspicuous organs could not possibly have been missed by generations of anatomists, we began reviewing all of the classical texts (some of them centuries old!) in search of a name for these organs. We found them in other, but not all, species of toads. Fully expecting to be humiliated by our fellow students, we started meekly asking around to see if anyone knew about these things. Finally, when our literature search and humble inquiries resulted in nothing, we started showing them to our fellow students. Nothing. Speechless. Nobody had noticed these obvious organs. Eventually, we got up the nerve to approach our graduate advisers—these two were literally the very top-tier of academia in the realm of frogs. We were anticipating a withering and patronizing response, reminding us of some obvious classical text (likely in German, from the 1700s) that had originally described these things. Nothing. Speechless. Wow. Their response was “Well, you two seem to have found something, so get to it and write that up!”

Our research found that these were a previously unknown fat-storage organ of some sort.  They were in a position in the body where fat was not known to be stored, and their cellular makeup was different from the well-known fat-storage systems in frogs. We named them as Inguinal Fat Bodies and speculated, based on the cellular composition, that they may play a role in maintaining water balance rather than the more typical food-energy storage role that we usually associate with fat. This might make them functionally somewhat like a camel “stores water” in its humps. Helping our preliminary case was the fact that species of toads that lived in deserts tended to have them, and have them in larger form than rainforest toads that had very small inguinal fat bodies or none at all. We published the description, our name for them, and our precocious speculations about their function. Over the years, I’ve been disappointed that a proper amphibian physiologist has never really taken up the obvious next questions about their function. A paper came out just a few years ago that did a more elegant job of correlating their presence and form with dry-habitat lifestyles. And, a friend helped us access an original copy of a 1758 anatomical masterpiece by the Swiss scientists Rösel van Rosenhof that had hand-colored lithograph plates. This copy was in the Special Collections Library at the Smithsonian Institution; it must be worth hundreds of thousands of dollars, so I was thrilled when I got to examine this treasure. This fellow van Rosenhof was no slouch, and there in Plate XXIV was a beautiful hand-colored illustration of a dissected toad that clearly showed our Inguinal Fat Bodies. But, they are not labelled and are never discussed in the text. So, he had noticed them, dutifully included them in his illustrations, but evidently gave them no further thought.

I’ve been very fortunate in my research career to have the joy of truly discovering new things. New species, new phenomena, etc., but this one on a late night in the lab with my best friend really struck me because it came after centuries of very able anatomists had described every minute aspect of a frog, or so we thought!  I wonder if my Dutch colleagues who found these new human salivary glands feel the same way?  I hope they do, because their findings are remarkable.

Indeed, sometimes the big discoveries are right under your nose. I think the secret there is less about looking diligently, but rather in sampling regarding and noticing. 
Thanks for your attentions to my long tale!

Link to new piece about the new salivary glands:
https://www.nytimes.com/2020/10/19/health/saliva-glands-new-organs.html

Joe Mendelson, PhD
Director of Research

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