Keep It Simple Students: Camouflage

In this series of posts, I have challenged science students to explain complex topics in as simple a manner as possible (but not simpler). In this post, 18-year old biochemistry student Henry Laney tackles animal camouflage and the awesomeness that is the mimic octopus.

Animal camouflage is a classic "gee whizz" moment. It's almost like an optical illusion. The picture of dirt that you've been staring suddenly reveals an evil looking frog looming out of the foreground. The sheer variety and ingenuity of animal disguises are, quite simply, breathtaking.

How camouflage evolves is straightforward-ancient populations that blended into their environment better had a longer life expectancy than their stick-out-like-a-sore-thumb peers. As a result, they produced more offspring, passing successful genes onto the next generation. Over many generations, all the un-camouflaged animals died or did not reproduce, until there were only camouflaged individuals.

There are numerous examples of camouflage in animals, which can be neatly grouped into passive and active camouflage.

Most animals use passive camouflage. At its simplest, it involves being a colour that is repeated in the environment. In fact, it's hard to find an animal that doesn't blend in with its natural surroundings in some way-unless it's poisonous, in which case it becomes as colourful as possible to warn any predators lurking around. Poison-arrow frogs are a beautiful example.

Other cases of passive camouflage are a bit fancier. Tigers and Leopards for example, have beautiful patterns to simulate the way that light falls in the forests where they hunt. It also serves to break up their outline. This is referred to as "disruptive camouflage".

There are many examples of how animals use visual cues to prevent detection. They range from hiding their shadow, to covering themselves in stuff from their environment (there is a crab in there, I promise), to countershading, which turns them into an optical illusion, and, my personal favourite, dazzle camouflage-typically stripes to confuse predators. Oh, and animals using this tactic look utterly fabulous...(and are the inspiration behind these magical watercraft).

The next level of passive camouflage is to actually take on the shape of something boring and uninteresting to predators/prey. This category of camo is mostly filled with insects turning into vegetation (stick insects, leaf bugs etc.). However, an excellent example of camouflage from the sea-a stonefish, with its excruciatingly painful venom-proves that it's not just spiders that have the monopoly on NOPE.

Now, we get to the fun bit, which is active camouflage. This is when an organism changes itself to match its surroundings. Those who may now be thinking "chameleon time!" are wrong because the chameleon doesn't change colour to match its surroundings, but instead its mood. Anyway, there are far more interesting examples. Peacock flounders for example can change colour to match most surroundings, even if it is a chessboard. Other fish such as the plainfin midshipman have a series of cells on the underside of the body that match the brightness and colour of the light filtering down from above them. Predators below them just pass on by, thanks to a process called counter-illumination.

Some species have even managed to change their shape, to mimic other species or inanimate objects for the purposes of camouflage. The undisputed star of this technique, Ladies and Gentlemen, is the mimic octopus. Nothing I write could ever, ever top that video, so I'm just going to move on. Animals aren't the only organisms that use camouflage.

The KSA herpesvirus is a small, vulnerable virus from the herpes family with an interesting version of active camouflage. Inflammation is a key weapon against viruses, and so to prevent this, the KSA virus causes the production of a decoy protein inside its host cell. This decoy interferes with a key molecule in a process that triggers inflammation. The decoy also prevents the host's immune system from deploying, allowing the virus to remain unnoticed. In camouflage terms, this is like poking out the eyes of the thing hunting you. So yeah, pretty active camouflage.

An example from the world of bacteria is the dreaded Salmonella bacterium. Instead of being ingested and destroyed by a macrophage-a white blood cell that "eats" bacteria and then dissolves them-it instead takes control of the macrophage, turning it into a place to safely reproduce, disguised from the immune system as the macrophage is still alive. It then bursts out of the macrophage in suitable chestburster-like fashion.

The comparison for animals would be being eaten by something and then using their body to reproduce (because a member of the opposite sex is in there as well), after which all your babies would burst out of the animal and go on to eat the rest of its kin.

And this is just a drop in the ocean-practically every animal on earth uses some kind of camouflage, ranging from the mundane to the sublimely arcane. But if there's one thing you learn from this article, it's that mimic octopuses (yes, octopuses), are badass. Go on, watch the video again. I know I will.

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Henry Lloyd Laney is an 18-year-old student currently taking a year out before applying to university for biochemistry and working in the molecular genetics department of his local hospital. He thinks viruses are probably more interesting than you, but remains eminently convincible.

Image Credit:

Mimic octopus doing a jelly impersonation by Daniel Kwok