Shark Colors 57that live at intermediate depths and that move up and down day and night
have dark backs while their lower surfaces are spotted with light organs
called photophores. Spined Pygmy Sharks, diminutive dalatiids (28 cm, or
11 in, in length), occur around 500 m (1,640 ft) by day but move up to
200-m (660-ft) depths at night. They have numerous small photophores
on their bellies right up to their snout. It is thought that these light or-
gans put out just enough light of the correct wavelength to match weak
downwelling light, thus obscuring their profile when viewed from below by
their predators. This so-called “ventral bioluminescence” also character-
izes many bony fishes, squids, and shrimplike animals that live at the same
depths.Are any sharks colorful?
Colorwise, sharks are pretty boring. Dominant colors are shades of gray
and brown, some darker, some lighter. Colorful sharks that deviate from
black, gray, and brown are definitely rare. Those that appear colorful—
with spots, stripes, bars, or blotches—are almost entirely small bottom-
living species that use their color patterns as camouflage, blending into the
varied-color background on which they sit. Bold marks may break up the
image of their body outline, making them unrecognizable as a shark. This
kind of patterning, referred to as disruptive coloration, is common in many
fishes, both predators and prey.
The squalomorphs, although taxonomically diverse, contain few sharks
that could be considered colorful in any sense of the word. Some angel
sharks (Squatinidae) have rings and spots on their bodies and pectoral fins.
Angel sharks live on or even buried in sandy bottoms, and the spots prob-
ably serve (somehow) as camouflage.
Most galeomorphs are countershaded or unimaginatively colored,The Portuguese Dogfish is a deep-dwelling, 1 -m-long ( 3 -ft) somniosid shark with the uniform dark coloration typical
of sharks that live in ocean depths beyond the reach of surface light. Photo courtesy of Maria Pickering