Gaze at a reef and you’ll see a vivid habitat- tan fire coral, purple gorgonians, red lacy-looking lionfish, and millions of other colors and corals. But what is more interesting is what you can’t see… and what’s in clear view telling you “don’t touch me”. In reefs all animals drape themselves in color or camouflage to entice mates, catch prey, or even hide in plain sight.
|Butterfly Fish (Ref 5)|
|Scorpianfish (Ref 10)|
Most of the angelfish and butterfly fish use disruptive coloring to break up their distinct shape and become more like the reef. Non-repetitive designs like spots or stripes may stand out in open water, but they become part of the menagerie of shapes in a reef. Queen and Emperor Angelfish are blue and yellow striped to blend in, and Threespot Flounder have eyes on their body to confuse predators.
Yet other creatures find different ways to hide. Toad fish, stargazers, and rays lie close to the bottom to eliminate their shadow, making them almost invisible to predators; they’re just a lump in the sand. Fish like lizardfishes and garden eels even bury themselves or dig holes. One rare fish that we have seen is the shortnose batfish that looks basically like a pancake with two legs, a tail, and a snoot. Many shells bury themselves in sand; the only giveaway is their track that weaves through the ripples of sand. Wobbegongs are flat and colored to the bottom, and they’re so confident in their camouflage they won’t move unless touched.
|Long Nose Batfish (Ref 4)|
The most breathtaking form of camouflage is self-decoration. Hermit crabs carry a heavy shell, Decorator Crabs load themselves with massive amounts of debris, and Carrier Shells glue on shell fragments in a spiral pattern. Many shells are smooth to repel such growths, but others, like the Atlantic Thorny Oyster give lots of protrusions to attract algae and coral.
|Carrier Shell (Ref 6)|
Trumpet fish and seahorses display cryptic behavior, mimicking the reef, whether that may be swaying soft corals or waving grasses. Razorfish and trumpetfish are long and skinny to look like a floating branch. Groupers and many other fish stay very still, relying on their coloring to stay inconspicuous. Trumpet fish are the funniest, for when they are approached, they stay very still, only moving to sway back and forth. Suddenly they start to change color and dart away to safety.
|Trumpetfish (Ref 8)|
What I think of as the best camouflage is changing color; the octopus, flounder, and squid do it well. Octopi not only use it to camouflage, they also use it to hunt. They drift over a patch of coral when they’re dark brown, and then stop and make their webbing white. Fish in the rocks think it’s an opening and dart into the octopus’s hungry mouth. When they’re still they change color rapidly to suit the coral, which is impressive considering they’re colorblind. Once we saw an octopus eating a conch, a few tentacles in and around it, but when he saw us he stopped and hastily changed color, not moving even when we were a few inches away, as if to say, “it’s mine, go away!”
|Octopus Eating Conch, can you spot him? (Ref 9)|
Open-ocean fish are often silvery or transparent to color themselves like the sea. Moon jellyfish are almost entirely clear; the only giveaway is their faint outline and slight shimmer. Fish like tuna are silvery to reflect light and appear blue from a distance. Some squid illuminate their underside with sparkles so as not to appear as a dark shape when viewed from below.
|Squid (Ref 7)|
Some animals have light-colored underbellies because they are "counter-shaded." They are darkest on their backs, which are most often in direct sunlight, and lightest on their undersides, where a predator would see against the sun. An effectively camouflaged prey may appear flat and insubstantial.
Some sea creatures use motion dazzle. Motion dazzle may degrade predators' ability to estimate the prey's speed and direction accurately, giving the prey an improved chance of escape. Motion dazzle distorts speed perception, and is most effective at high speeds; stripes can also distort perception of size (and so, perceived range to the target). One example is a school of moving striped fish, such as razor fish and striped catfish.
|Striped Catfish (Ref 13)|
Underwater, the most complicated disguise is the art of using depth and color. As you may know, colors disappear with the reds and oranges fading first. Longer wavelengths of reds and oranges are quickly absorbed by the water. Damselfish, angelfish, and wrasses decorate themselves with these colors so that their color fades and blends, with depth, into the colors of the background, blue, green, and yellow dominating. Clouds of angelfish, and damselfish would blend their colors into a collage of multi shaded masses, stripes and spots helping to weave the pattern of the busy reef habitat. The more fish, the merrier, with such an excess of pattern and color, no one creature stands out. You can easily imagine how a predator would have trouble picking a single fish from a school of similar color, constantly moving.
|Anthias Normal (Ref 11)|
But, the color so useful in fading away can also be used to stand out. Fish use vivid displays of color to communicate their love to mates… or to warn away unwanted guests. Masters of beauty, Athias, appear drab normally, but erect their dorsal fins and blare their colors to attract a mate. The show doesn’t last for long though, the colorful performance exposing them to great risk from predators. The ability to change color is a class of skin cells
called chromatophores that show color through light manipulation or pigmentation. Chromatophores can instantly mark their bearer as terrifying, invisible, or irresistible.
|Anthias Courting (Ref 12)|
Some other colorful examples are Stonefish, who use their brown exterior to be invisible, but when frightened, open their colorful pectoral fins to warn off predators, “Stay away, I’m poisonous!”, and cleaner shrimp, who are not only colorful, but at a depth seem black and white, where red turns black.
In the underwater world, those who stand out and stay still clearly have a meaning. Bold colors can advertise danger. Clown fish sit in stinging anemones, lionfish are poisonous, and scorpion fish are too.
Fire urchins are red, yellow, purple and blue, able to stand out at any depth, and blast the message: toxic. One day I saw a ray that was unfamiliar to me. It was sitting on the bottom innocently covered with sand, and stupid me wanted to see what color it was. I dove down to the bottom and touched it to make it move, since it clearly wasn’t afraid- bad mistake. Zzzzzzt! I received an electric shock; I later learned it was a lesser electric ray. I never did see its color, but lesson learned, and I didn’t try to touch it again. Just yesterday, we saw an Atlantic Torpedo, able to produce enough electricity to stop a man’s heart.
|Torpedo Ray (Ref 14)|
But, if a fish wanted to attract a mate without being seen, how would he do it? To solve this problem Damselfish use reflectors to flash UV signals to communicate with others, and predators can’t see it. A male Squarespot Anthias is red and orange in normal light, at eighty feet is blue and purple, but in UV light is dark with a brilliant white spot, an easily seen signal to others of his kind, but not predators.
Every creature is exceptional in its own way, a majority amazing in camouflage. Others have found a way to stand out, extraordinary and bathed in color.
2. National Geographic Vol. 209 NO. 5 May 2005
3. Reef Fish Identification, Tropical Pacific
7. a-z animals.com