Gaze at the vivid yellows, blues, and psychedelic swirls of a single emperor angelfish and you'll sense the whimsy of evolution. Go on to explore its home in lush coral reefs and you'll soon hit sensory overload, assaulted by colors and patterns that range from sublime to garish. Coral reefs are unquestionably the world's most colorful places. But why?
For reasons known only to nature, color explodes across coral reefs, making them Earth's most vivid landscapes. Here in the shallows of a Fijian reef, brilliant soft corals wave in reds, pinks, and yellows as schools of fairy basslets flash orange and violet hues. The basslets' different colors aid in species identification, mate recognition, and even camouflage as individuals mass against the kaleidoscope of the reef. What humans see lighted by a photographer's bright strobe may look altogether different in natural light through the eyes of reef creatures. Scientists are now beginning to learn how wavelengths of light (and therefore color) change through water at different distances, and—more important—how fish see colors and what messages they might communicate.
Bold horizontal bands of black, white, and yellow pop out on a well-lighted sweetlips (Plectorhinchus polytaenia) in Indonesia. The pattern and colors actually help distort the fish's outline when seen in natural light at a distance through water, helping the animal disappear from the view of potential predators. Nearby, a neon cleaner wrasse also wears stark stripes. These little fish eat parasites off the flesh and mouths of other fish. The wrasse's stripes may signal that it is a useful helper rather than a ready meal. Neon wrasses vary in coloration geographically. A yellow cast near the head (as shown here) indicates an Indonesian species; in Fiji many neon wrasses have a yellow blaze near the tail.
在印度尼西亚，这条被照亮的多纹石鲈(Plectorhinchus polytaenia)身上大胆的黑、白、黄相间水平条纹蹦现了出来。其实，若是在自然光下、于水中一段距离外，这种图案和色彩有助于扭曲鱼的轮廓，让它在潜在掠食者的视线中消失。旁边，一只裂唇鱼（neon cleaner wrasse）也是十足的条纹。这种小鱼以其它鱼类身上、口内的寄生虫为食。它身上的条纹可能暗示它是有用的帮手，而非一顿餐点。随地点不同，裂唇鱼的色彩也会改变。靠近头部有一抹黄色的（如图）表示是印度尼西亚种类；在斐济，许多裂唇鱼在靠近尾巴的地方有黄色条纹。
The Pacific blue tang (Paracanthurus hepatus)—also known as the artist's pallette surgeonfish due to the shape of the dark patch on its body—was immortalized by the character Dory in the film Finding Nemo. Unlike that benignly daft creature, this real-life surgeonfish in Indonesia carries a sharp retractable blade of bone near the base of its tail. The tail's yellow blaze gives potential foes fair warning: Armed and dangerous.
A leaf scorpionfish (Taenianotus triacanthus) scouts for errant fairy basslets in Fijian waters. This ambush predator can change its color to blend with its surroundings. It then lies still, waiting for prey to pass by. "We saw this fish pounce a couple of times," says photographer Tim Laman. "His mouth shot out and back in a fraction of a second."
A crescent-tailed bigeye (Priacanthus hamrur) seems to wear its emotions on its sleeve—or on its whole body. This sequence of three frames of the same fish shows how it can change from largely silver to striped to solid orange-red, a transformation that occurs in a matter of seconds. Pigment cells in its skin, called chromatophores, allow it to change color, but scientists don't yet know what each color pattern signifies. Sometimes a sudden shift in color can be used to startle potential predators or threaten intruders. Red light dissipates beyond about 30 feet (10 meters), so the reddish hue of this fish would appear black in deeper waters, allowing some degree of invisibility for this nocturnal hunter.