Chameleons of the Sea

Small animals on the reef are in constant danger of ending up as a snack for the ever-hungry predators patrolling the area.This fact of life has driven the evolution of some remarkable adaptations, not least those used by reef animals to blend into their background. For camouflage to be most effective, animals must not only match their color to the surrounding habitat, but also manage to break up the outline and contours of their body.

How common is camouflage among reef animals?

In the predator-rich world of the coral reef, it pays to keep a low profile and camouflage is an extremely common strategy. It is especially frequent among animals closely associated with a particular microhabitat within the reef. There are many examples of gobies that are exquisitely matched to their habitat, particularly coral gobies. Invertebrates, too, use camouflage extensively.The candy crab, for example, is perfectly adapted to blend in against the soft coral among which it lives.

What is contour elimination?

Many fish predators operate by forming a search image; their mind focuses on finding fish-shaped objects. Prey animals work in the same way when they are keeping an eye out for an approaching predator. Contour elimination, as the term suggests, works by breaking up this outline and is a key part of blending into the background.The decorator crab is covered in tiny hairs that work almost like Velcro. The crab covers itself in pieces of debris and aquatic bric-a-brac that it comes across until ultimately it ceases to look like a crab at all.

It has also been suggested that stripes, especially vertical stripes such as those of Moorish idols, are also highly effective in breaking up an animal's outline. Predators, such as scorpionfishes and frogflshes, also use contour elimination to prevent their prey from detecting and avoiding them. These bottom-living fish often have a ragged fringe around their bodies. When viewed from above, it helps them blend in against the corals. Most highly camouflaged animals, including those that use contour elimination, keep very still for large portions of their day; any movement would counteract the effectiveness of their disguise.

Who are the real marine chameleons?

Flatfish, such as plaice and flounder were once considered the masters of disguise, changing color to match the substrate on which they lie. However, the real champions are arguably the seahorses. In common with flatfishes, they are able to adapt their coloration to match their surroundings, a quality known as adaptive camouflage.

Furthermore, many seahorses are able to match not only the color of their habitat but also its texture.They display amazing patterns of contour elimination as well; the incredible leafy sea dragon (Phycodurus eques) is a good example of this.The related pygmy seahorses (Hippocampus bargibanti) live among soft corals and are almost impossible to detect, even at close range, so well do they match their surroundings. If transferred to a new sea fan, they rapidly take on both the color and texture of their new host.