Camouflage

Hiding is a key strategy for survival for many marine animals. Some physically hide in holes, crevices, under rocks or even inside other creatures, coming out to feed only when it is safe, whereas others hide in the open using their special colours and patterns, or have the ability to change colour, or they can attach other animals and plants to their bodies to produce a complete disguise. Sometimes these disguises are so good that we often don’t see them at all, or only when they move, and sometimes, as in the case of the stonefish or stingray, their late discovery can be catastrophic. Camouflage helps both the hunter and the hunted – both remaining still, ready to pounce or to avoid being eaten.

Bold-spot Anemone Shrimp (Thor amboinensis) Bold-spot Anemone Shrimp (Thor amboinensis), Photo courtesy of Ian Banks.Other marine animals adopt a different tactical camouflage, having showy, intricate or delicate features that attract instant attention – and presumably those of their predators – including flamboyant colours or appendages. These features have evolved for specific purposes to assist their survival in the sea, although the purpose of the persistence of flamboyant characteristics is probably intricate and multifold, ranging from attracting mates to warning off predators. The masters of these disguises are the nudibranch molluscs (naked-gilled sea-slugs) and marine flatworms (turbellarian Platyhelminthes). Together these include some of the most colourful and intricately patterned of marine invertebrates. Many have bright and elaborate colour patterns as spectacular as those seen in butterflies. Like butterflies these colour patterns serve to warn-off predators that they are toxic or taste bad. In the case of nudibranchs these creatures may produce their own toxins or modify them (sequester) from their diet, which is often sponges, with the new toxins more potent than the original ones. Some nudibranchs even feed on fire corals and keep their stinging cells to use for their own defense. Other nudibranchs and flatworms are not actually toxic but have evolved the colour patterns of toxic species as a defensive mechanism against predators where they pretend to be dangerous (mimicry).

Many other marine species have evolved disruptive colour patterns to make themselves difficult to detect by either predators or their prey. Unlike camouflage, which imitates the background to make the creature invisible, disruptive colouration uses spots, stripes or other obvious patterns to visually confuse potential predators. Colour patterns that may appear bold and striking can break up the outline of an animal to the extent that the observer will overlook it – like zebras on the land. The predator’s eye focuses on the markings so that the striped animal virtually disappears without trace.

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