Deep Sea Angler fish

Today we know of more than 200 different Angler fish species from a wide range of different families and genera. What they all have in common is that they use their modified first spine to attract unsuspecting prey. This modified first spine is named illicium and on its top you can see a fleshy growth; a so called esca. The Angler fish use the illicium and esca to attract other predatory fish that mistake the growth for a tasty prey. When the predatory fish is close enough, the Angler fish will make a rapid attack and devour it. Angler fishes are renowned for catching prey that is much larger than them. To be able to swallow and digest huge preys, the Angler fish have jaws that can be distended, thin and flexible bones and an expandable stomach

The various Angler fish species all belong to an order named Lophiiformes; the bony fish order. Most Angler fish are so called deep sea angler fish species that live far down in the ocean in the so called aphotic zones, but a few families also contain shallow water Angler fish. In aphotic environments, the deep water makes it impossible for the sunlight to penetrate all the way down. This means that a traditional illicium and esca can be quite useless, since it will not bee seen in the dark waters. Many deep sea angler fish species have therefore formed a symbiotic relationship with bacteria. Bacteria live in the esca and produce light that can be detected by predatory fish, so called bioluminescence. Since many other creatures use bioluminescence to communicate in this dark environment, the predatory fishes will think that the light is sent out by a small animal and try to eat it. The deep sea Angler fish is virtually invisible in this environment and can easily ambush the predatory fish. A deep sea Angler fish is black, gray or dark brown and the light that is emitted by the bacteria or by other luminescent animals is not strong enough to make the body of the Angler fish visible.

Deep Sea Angler Fish Breeding Behaviour

Finding a mate is complicated in a pitch black environment and some deep sea Angler fish species have therefore developed a truly remarkable mating method. In order to always have a suitable mate ready for breeding, the female Angler fish allows a male Angler fish to attach himself to her and live as a form of parasite for the rest of his life. The female Angler fish is therefore much larger than the male. Female Angler fish that exceeded one yard (91 centimeters) have been found in the ocean, while males tend to stay around 4-6 inches long.

The female deep sea Angler fish will release the eggs and they will float all the way to the surface. The fry is eventually hatched and begin to feed on tiny plankton. Young deep sea Angler fish have balloon shaped bodies and under the skin of a young deep sea Angler fish you will find a layer of gelatin. The illicium begin to form on the females while they are still quite young. The male will instead form pincer like teeth that he will need as he matures and tries to attach himself to a female. Metamorphosis typically occurs at about 3,000 feet and it is only very young deep sea Angler fish that can be found at the surface. As the male matures, he will try to locate a female Angler fish from the same species. We still do not know exactly how he does this, but pheromones probably play an important part. Young male deep see Angler fishes have highly sensitive olfactory organs. It is also possible that they males are attracted by the glowing illicium of the female. When a male finds a female, he will use his teeth to attach himself to her skin. He will secrete an enzyme that slowly combine the two fishes and fuse their blood systems together. After a while, his mouth will have become permanently joined to the skin of the female and she will always swim with him in tow. Males relay on females for their survival since they have no digestive system and no illicium. Eventually, the attached male will degenerate into hardly more than a pair of gonads. The gonads will release sperm when the female is ready to release eggs