This striking image is not the latest Hollywood alien, but actually a microscope image taken of an embryonic Little skate – a fish closely related to the shark family.
Like sharks, the Little skate has a skeleton made not out of bone, but cartilage. They may seem very different to us, but these cartilaginous fish have a number of features which betray their close relationship to humans. For example, human embryos develop a skeleton made of cartilage first. Only later on is this added to with bone cells and calcium minerals in a process known as ossification.
And, like the video points out we have very similar genes to the ones that control the denticles of the skate. Weirdly though, the genes that create the skate’s scales are not similar to the the ones responsible for our skin, but for our teeth. The structure of the denticle, or placoid scale, is strikingly similar. It has a central cavity filled with blood vessels, which is surrounded by dentine, just like human teeth. It even has an enamel-like coating on top. Its not too misleading to say, therefore, that skates are covered in tiny teeth.
The research done on this fish was carried out by someone with the slightly appropriate name of Dr Gillis. His website contains a lot more beautiful images of skate embryos and is well worth checking out.
FYI
- The Largest Stingray ever caught weighed over 770 pounds.
- A great collection of videos showing science under the microscope, by Cambridge University.
- One human ancestor had the sixth sense of electroreception – we lost it millions of years ago unfortunately (with the exception of Bruce Willis).
- Most species of stingray are venomous; their stingers house two grooves containing potent venom glands.
