Continuing to read Immense World by Ed Yong. I ordered his previous book, “I Contain Multitudes,” about the microbiota. But that’s for later. Currently, there’s an intriguing story unfolding from the pages as I read.
In previous posts, I mentioned that Catfish — those whiskered little fish — have taste receptors all over their bodies, from head to tail, numbering between 100,000 to 150,000. For comparison, humans have about 9,000, and chickens — 24. Thus, their life at the bottom in murky and muddy water is made easier as they can taste the water with their entire body.
I am now reading that in 2012, Daphne Soares, a biologist from the nearby University of Maryland, discovered something interesting about the Astroblepus Pholeter catfish from a cave in Ecuador. She found that these blind catfish evolved in the turbulent currents of the cave in such a way that their skin became covered with what she called “micro-joysticks,” but the interesting part is not just that, but that these “micro-joysticks” are essentially teeth. They don’t look like teeth, but they are indeed made from enamel and dentin, with nerves connecting to all of this. These tooth-like formations on the skin are called denticles.
There are other fish with denticles, but usually, they use them as a “tool” for “cutting,” as well as for protection, or for reducing resistance while swimming. However, cave catfish use these denticles as mechanosensors for navigation in dark and fast-flowing environments, needing more robust sensors, much like how other fish use the lateral line.
Incidentally, on Daphne Soares’ personal website, among the list of discoveries is also the previously unknown sensory organ in alligators — integumentary sensory organs (ISOs). They appear as black dots of about half a millimeter on the alligator’s face. With them, crocodilians feel water disturbances and changes in pressure (which are essentially the same thing). And they are very sensitive — able to detect water movements as small as 4 micrometers, which is less than the thickness of a human hair.
It also turns out that male alligators can produce very low sounds, which are detected by the female with these sensitive cells on the snout. It is unknown what the female then does with this information, but at least she’s now informed. Unknown what you will do with all this information, but at least you are now informed as well.
Hi, I'm Rauf Aliev. 