Editing Camouflage (section)

=== Silvering ===

[[File:Herringadultkils2.jpg|thumb|left|upright=1.15|The adult herring, ''[[Clupea harengus]]'', is a typical silvered fish of medium depths, camouflaged by reflection.]]
[[File:Herring Silvering.jpg|thumb|upright=0.7|The herring's reflectors are nearly vertical for camouflage from the side.]]

Where transparency cannot be achieved, it can be imitated effectively by silvering to make an animal's body highly reflective. At medium depths at sea, light comes from above, so a mirror oriented vertically makes animals such as fish invisible from the side. Most fish in the upper ocean such as [[sardine]] and [[herring]] are camouflaged by silvering.{{sfn|Herring|2002|pages=192–195}}

The [[marine hatchetfish]] is extremely flattened laterally, leaving the body just millimetres thick, and the body is so silvery as to resemble [[aluminium foil]]. The mirrors consist of microscopic structures similar to those used to provide [[structural coloration]]: stacks of between 5 and 10 crystals of [[guanine]] spaced about {{frac|1|4}} of a wavelength apart to interfere constructively and achieve nearly 100 per cent reflection. In the deep waters that the hatchetfish lives in, only blue light with a wavelength of 500 nanometres percolates down and needs to be reflected, so mirrors 125 nanometres apart provide good camouflage.{{sfn|Herring|2002|pages=192–195}}

In fish such as the herring which live in shallower water, the mirrors must reflect a mixture of wavelengths, and the fish accordingly has crystal stacks with a range of different spacings. A further complication for fish with bodies that are rounded in cross-section is that the mirrors would be ineffective if laid flat on the skin, as they would fail to reflect horizontally. The overall mirror effect is achieved with many small reflectors, all oriented vertically.{{sfn|Herring|2002|pages=192–195}} Silvering is found in other marine animals as well as fish. The [[cephalopods]], including squid, octopus and cuttlefish, have multilayer mirrors made of protein rather than guanine.{{sfn|Herring|2002|pages=192–195}}