For the third fact of Christmas, let’s learn about three French hens. Now, the song mentions hens, but doesn’t go into any more detail. That’s ambiguous, as a “hen” could refer to a female game bird (duck, chicken, turkey), or just as easily mean a female octopus or lobster. Or perhaps the song is being casual in referring to three ladies from France. Hmmm.
Let’s go with… the octopus! I think it’s the most interesting of the bunch for one very special reason. The octopus is perhaps nature’s foremost master of camouflage.
Octopodes have special skin cells called chromotaphores, also found in many amphibians, fish, and reptiles such as the famous chameleon. But the chameleon has nothing on the octopus for colour changing talent. An octopus can quite literally disappear into its surroundings in the blink of an eye. It can see the surface that it wants to rest on, then mimic the colour and texture of that surface.
Really, I don’t think I could write enough for you to believe how good they are at this, so I’ll just show you this video. It looks like a magic trick, or special effects, but this is real.
So how does this happen? In cephalopods (which include octopodes, squid and other squishy tentacled things) the chromatophore cell contains tiny bits of pigment enclosed in a flexible sac, which can be moved with muscle control. Contracting the cell can change the reflectivity, translucency, or opacity of that individual cell instantly. The octopus can change colours by thinking just the same as you wiggling your fingers.
With complete control over every “pixel” of its skin, the octopus could potentially display a photograph, if it could just think it. In fact, the octopus will use its colour changing for communication as well as camouflage, visually signalling other octopodes.
On that note, I found one more mind-blowing thing. Cuttlefish (a cephalopod much like an octopus) have been found to use polarization to send secret messages. Polarization, for a quick overview, is commonly experienced in 3D movies. One side of the special glasses will only let half of the light through (the light that matches the polarization of the lens) so each eye sees a different image. Water causes light to become polarized, and to a cuttlefish, which seems to have its own version of 3D glasses, this means they can see things other seas creatures cannot. Add in the fact that they can control the polarization of light bouncing off their own skin to make hidden patterns and voila… encoded messages.
So, clearly, they are the ninja-special-ops-secret-agent of the sea, and they may be working for France, and that is your third fact of Christmas!