Ceratiidae

Sea devils are the family of deep-sea anglerfish known as the Ceratiidae,[1] from the Greek keras, "horn", referring to the bioluminescent lure that projects from the fishes' forehead.

Sea devils
Krøyer's deep sea angler fish, Ceratias holboelli
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Actinopterygii
Order:	Lophiiformes
Suborder:	Ceratioidei
Family:	Ceratiidae T. N. Gill, 1861
Genera
Ceratias Cryptopsaras

Female with a parasitic male, preparation at the Saint Petersburg Zoology Museum

They are among the most widespread of the anglerfishes, found in all oceans from the tropics to the Antarctic. They are large and elongated: females of the largest species, Krøyer's deep sea angler fish, Ceratias holboelli, reach 1.2 m (3.9 ft) in length. Males, by contrast, are much smaller, reaching 14 cm (5.5 in), and, like other anglerfish males, spend much of their lives attached to a female after a free-living adolescent stage in which they are very small – at most 1.3 cm (0.51 in) – and have sharp, beak-like, toothless jaws.[2] One or more males attach themselves permanently to a female, eventually merging circulatory systems. As this genetic chimera matures, the male grows large testicles, while the rest of its body atrophies. Ceratiidae are the only creatures known to become chimeras as a normal part of their lifecycle.