BIOLUMINESCENCE
In the darkness of the twilight zone, light is an important way for animals to communicate, hunt, find a mate, and avoid being eaten. The light can be almost any color, but blue travels the farthest in seawater before being absorbed. Many bioluminescent organs in fish and other organisms are filled with bacteria that the animals must acquire after birth.
MARINE SNOW
Marine “snow” is not actually snow at all, but particles of organic (carbon-containing) material that drifts continuously from the surface to deeper waters, providing food for many species. It is also an important way for carbon to move from surface waters to the deep ocean, where it can be locked away for hundreds or thousands of years.
SALPS
Salps are gelatinous organisms can form chains up to 130 feet long, making them the longest animal on Earth, and often form dense swarms. They feed continuously on organic matter in the water and produce dense fecal pellets that sink rapidly into the depths. Large swarms of salps may be an important part of the global carbon cycle.
BRISTLEMOUTHS
The bristlemouth is a tiny fish only about 3 inches long and is believed to be the most abundant vertebrate on Earth, numbering perhaps in the hundreds of trillions or quadrillions.
PREDATORS
Many large predators such as some sharks, whales, and squid make frequent trips into the twilight zone to feed, providing an important ecological link between surface and deep ecosystems.
ANGLERFISH
Anglerfish use a bioluminescent appendage to lure prey close to their mouth, but only the females. Male anglerfish are tiny and attach themselves to their mate, after which their eyes and many of their internal organs wither away.
MIGRATION
The largest animal migration on Earth occurs every day as many twilight zone residents around the globe move up into surface waters at night to feed and back down into the darkness during the day to avoid predators. Their motion is believed to help mix the ocean.
JELLYFISH
There may be many undiscovered species of jellyfish in the twilight zone. Their delicate gelatinous forms are easily damaged when they are collected in nets and trawls making identifications difficult. Jellyfish are characterized by having stinging structures called nematocysts, unlike the more complex but non-stinging gelatinous salps.
LANTERN FISH
There may be many undiscovered species of jellyfish in the twilight zone. Their delicate gelatinous forms are easily damaged when they are collected in nets and trawls making identifications difficult. Jellyfish are characterized by having stinging structures called nematocysts, unlike the more complex but non-stinging gelatinous salps.