Transparency
We begin this chapter by considering the ecological distribution of transparent organisms and, in particular, how they are found predominantly in one particular habitat type (open waters); we aim to explain this trend. A perfectly transparent organism (or part of an organism) will not absorb or scatter incident light. Superficially, transparent might seem like a synonym for visually undetectable, but this is not quite true: we discuss how transparent organisms can still be visually detected by their predators or prey. Conversely, there are circumstances where a little transparency can go a long way to reducing an organism’s visibility. Some body parts cannot be made transparent, but we argue that opaque body parts need not always significantly increase the detectability of a generally transparent organism. We will then consider the distribution of transparency among natural organisms. The distributional observations we seek to explain are: the greater prevalence of transparency among aquatic than terrestrial organisms, and the particular prevalence among midwater species. An alternative but related strategy to transparency, adopted by some midwater fish, and considered later in this chapter, is silvering of the body to provide crypsis by broadband reflection.