Mimicry: An Effective Defense Against Reef Predators
Given a choice between tackling an angry moray eel or a small, inoffensive morsel of a fish, there are no prizes for guessing which one a predator is likely to opt for. But if the small fish in question can fool the predator into thinking it is a moray eel, then it is very likely to be left alone.
The remarkable coloration and pattern of the comet (Calloplesiops attivelis) is thought to mimic whitemouth moray eels. The comet seeks refuge headfirst, so that its flowing fins and startling eyes pot remain exposed, looking like the protruding head of a fearsome moray eel, something that few hunters will willingly tackle. The comet even takes things a step further if threatened and has mastered the art of swimming backwards. When it does so, the appearance is startlingly like that of a moray eel swimming forwards. Mimicry such as this is fairly common on coral reefs. Many harmless organisms mimic more dangerous or poisonous species (known as Batesian mimicry) and some predators mimic harmless fish to get up close to their prey (known as aggressive mimicry).
Can you always believe your eyes?
Comets are not the only fish to use eyespots, or ocelli, to confuse predators. Eyespots are a simple but ingenious way of confusing predators. Firstly, the eyespots that fish such as butterflyfish incorporate into their color patterns are usually larger than their own eyes. This is important, because there is evidence to suggest that predators use the size of their prey's eye to gauge how large they are, especially when they cannot see the whole of their quarry's body. This is particularly the case in many wrasse species, gurnards, and crab eye gobies; the dual eyespots of these fishes may momentarily convince predators into thinking that they have come face to face with a really huge animal! If they can be confused into thinking that the large eyespot belongs to a large fish, they will be less likely to attack.
Secondly, the eyespot tends to be located towards the rear of the body, while the real eyes are partially masked by a band of coloration. If and when a predator attacks, its prey will escape in exactly the opposite direction to that which the predator would expect! Finally, eyespots are also thought to direct attacks away from the head area and towards the less vulnerable tail area.
What is meant by "deflective coloration"?
Any color pattern that fishes use to redirect a potential attack away from the head and eyes and towards a different part of their body is referred to as deflective coloration. Eyespots fall into this category, but are not the only type. An impressive example is seen in juvenile emperor angelfishes, whose mesmerizing concentric bands are thought to achieve the same effect. Interestingly, a number of predators have a similar strategy, using color patterns to draw prey fish closer, a phenomenon known as directive coloration. Examples include the lures, often shaped like worms, used by some anglerfishes, and the vividly colored mouthparts of stargazers.