Science Fair Project Encyclopedia
Anglerfish is the common name for the 200+ species that comprise the bony fish order Lophiiformes. They are for the most part deep-water fishes, although there are some anglerfish families that have shallow-water representatives, and one family, the frogfishes (Family Antennariidae), occurs only in shallow water. Examples of other anglerfish families that have some shallow water species are the monkfish or goosefish, (Family Lophiidae) and the batfishes (Family Ogcocephalidae). These families also have deep water representatives. The deep-sea mid-water anglerfishes belong to the suborder Ceratioidei and are usually referred to as ceratioids.
Anglerfish are named for their characteristic method of predation, which involves the use of the modified first spine from the first or spinous dorsal fin. This spine (the illicium) protrudes above the fish's eyes, with a fleshy growth (the esca) at the tip of the spine (the netdevil anglerfish has similar growths protruding from its chin as well). This growth can be wiggled so as to resemble a prey animal, and thus to act as bait to lure other predators close enough for the anglerfish to devour them whole. To accomplish this, the anglerfish is able to distend both its jaw and its stomach (its bones are thin and flexible) to enormous size, allowing it to swallow prey up to twice as large as its entire body.
As most anglerfishes live mainly in the oceans' aphotic zones, where the water is too deep for sunlight to penetrate, their predation relies on the "lure" being bioluminescent (via bacterial symbiosis). In a related adaptation, anglerfish are dull gray, dark brown or black, and are thus not visible either in their own light or in that of similarly luminescent prey.
Some anglerfish have a unique mating method. Without light, finding a mate is a problem, especially at a time when both individuals are ready to spawn. When scientists first started capturing ceratioid anglerfishes, they noticed that all of the specimens were females. These individuals were a few inches in size and almost all of them had what appeared to be parasites attached to them. It turns out that these "parasites" were the males. When a male anglerfish is hatched, he has extremely well developed olfactory organs that detect scents in the water. He has no digestive system. His goal in life is to detect the pheromones that the female anglerfishes release. When he finds a female, he bites into her flank which releases an enzyme that digests the skin of his mouth and her body. The two then fuse together, including blood vessels. The male degenerates into nothing more than a pair of gonads that releases sperm when the female releases hormones into the bloodstream that signals she is ready to release her eggs. This is an extreme example of sexual dimorphism. If the male anglerfish doesn't find a female, he dies.
An anglerfish was featured on the popular Pixar movie "Finding Nemo"
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