Who here has not considered the infinite possibilities with the power of invisibility? How you could improve your life, and sift through it unseen. So have the cephalopods of the animal kingdom considered the possibilities. And being equipped with their highly evolved pigmentation (known as chromataphores, which are in a sense pigmented muscles connected to the brain) (Mäthger & Hanlon 2012), certain cephalopods managed what men only can dream of. Invisibility.
Actually, what it really is, is transparency. By completely contracting their chromataphores they reveal the transparent muscle tissue, and basically turn their whole body invisible (Mäthger & Hanlon 2012). Like this little weirdo:
This is but one way cephalopods can become invisible. Many cuttlefish, octopi and squids can camouflage against complex backgrounds, like coral reefs or kelp forests (Hanlon et al 2009).
There have been some speculations into the different ways cephalopods camouflage, with there being three found so far; uniform (adapting color of background), mottle (adapting color, pattern and texture of background), and disruptive (additional input in mottle and/or uniform camouflage) (Hanlon et al 2009). Disruptive is the most interesting one, where the individuals seem to add a distinct feature within the camouflage (Figure 1), as if adding a personal touch. An example could be black spots in the middle of their camouflage.
Figure 1: Cuttlefish camouflaging against heterogeneous substrate using the disruptive method
What is really interesting is how these animals can distinguish the different colors when, in fact, they have been proven to be colorblind (Hanlon 2007). In an experiment to see the extent to which cephalopods could hide in plain sight, Hanlon (2007) found that the cephalopods would camouflage against a checkerboard made of highly contrasting shades of yellow and blue, using the uniform tactic. However, when set in a natural environment, they seem like the ultimate masters of disguise. With regards to their color blindness, going transparent would seem like the go-to technique, with limited effort put into trying to decipher the color spectrum of the intended background.
So, to address the initial title of this post, what really is the best approach for invisibility? Transparency or camouflage? To answer this question properly, and allow more room for discussion, I have decided to split this piece into two parts, where this post works as an introduction into the discussion.
This piece is taking a slightly different path than I intended when I initially started this blog, meaning it diverges slightly from looking into the evolution of this particular defense mechanism. However, I found in the end that discussing what tactic is the ultimate invisibility technique would be more interesting and challenging.
Hope to see you back next week when we will try to find the answer.
Here is some food for thought until next week.