VANISHING ACT

GHOST SHRIMP

Many shrimps worldwide have exoskeletons that are to varying degrees see-through. We can gawp at their inner workings, watch their last meal being digested and – in females – see bundles of eggs developing. In the watery realm that these crustaceans inhabit, transparency is a highly effective vanishing act, enabling them to merge with their background, whether open water, seabed or reef. Transparency is relatively straightforward for an aquatic species such as a shrimp, since the refractive index of water is far higher than that of air, and conveniently close to that of the animals’ exoskeleton and other tissues. There’s little or no difference in how light passes through water and their bodies, so they disappear. Some tiny marine shrimps have evolved an intimate relationship with sponges, clams and anemones, seldom straying from their host. The ghost shrimp pictured below is resting on its glass sponge home.