The angry-looking deep sea angler fish has a right to be cranky. It is quite possibly the ugliest animal on the planet, and it lives in what is easily Earth's most inhospitable habitat: the lonely, lightless bottom of the sea.
There are more than 200 species of anglerfish, most of which live in the murky depths of the Atlantic and Antarctic oceans, up to a mile below the surface, although some live in shallow, tropical environments. Generally dark gray to dark brown in color, they have huge heads and enormous crescent-shaped mouths filled with sharp, translucent teeth. Some angler fish can be quite large, reaching 3.3 feet (1 meter) in length. Most however are significantly smaller, often less than a foot.
Their mouths are so big and their bodies so pliable, they can actually swallow prey up to twice their own size.
Some deep-sea anglerfishes of the bathypelagic zone emit light from their escas to attract prey. This bioluminescence is a result of symbiosis with bacteria. Although the mechanism by which ceratioids harness them is unknown, the bacteria have been speculated to enter the esca from the seawater through small pores. One within the esca, they can multiply until their density is such that their collective glow is very bright.
