<P> The name "anglerfish" derives from the species' characteristic method of predation . Anglerfish typically have at least one long filament sprouting from the middle of their heads, termed the illicium . The illicium is the detached and modified first three spines of the anterior dorsal fin . In most anglerfish species, the longest filament is the first . This first spine protrudes above the fish's eyes and terminates in an irregular growth of flesh (the esca), and can move in all directions . Anglerfish can wiggle the esca to make it resemble a prey animal, which lures the anglerfish's prey close enough for the anglerfish to devour them whole . </P> <P> Some deep - sea anglerfish of the bathypelagic zone emit light from their esca to attract prey . This bioluminescence is a result of symbiosis with bacteria . The mechanism that ceratioids use to harness them is unknown, but researchers speculate that the bacteria enter the esca through small pores from seawater . Once inside, they multiply until their density is sufficient to produce a bright collective glow . </P> <P> Because anglerfish are opportunistic foragers, they show a range of preferred prey with fish at the extremes of the size spectrum, whilst showing increased selectivity for certain prey . One study examining the stomach contents of threadfin anglerfish off the Pacific coast of Central America found these fish primarily ate two categories of benthic prey: crustaceans and teleost fish . The most frequent prey were pandalid shrimp. 52% of the stomachs examined were empty, supporting the observations that anglerfish are low energy consumers . </P> <P> Some anglerfish, like those of the Ceratiidae, or sea devils employ an unusual mating method . Because individuals are locally rare, encounters are also very rare . Therefore, finding a mate is problematic . When scientists first started capturing ceratioid anglerfish, they noticed that all of the specimens were female . These individuals were a few centimetres in size and almost all of them had what appeared to be parasites attached to them . It turned out that these "parasites" were highly reduced male ceratioids . This indicates some taxa of anglerfish use a polyandrous mating system . </P>

What is the light on an angler fish