Triplewart seadevil

The Triplewart seadevil, Cryptopsaras couesii, is a seadevil of the family Ceratiidae, found in all oceans, from the surface to 1.24 mi (2,000 m). Its length is approximately 11.81 in (30 cm).

The Triplewart seadevil is one of the most abundant of the deepwater anglerfish. These fish have round flabby bodies with a soft fibrous skeleton and a scaleless prickly skin. Like most other deepwater anglerfishes this fish has small eyes, no pelvic fins and is colored black. It has a large vertically-directed mouth, and a fishing lure (illicium) on top of the head topped by a luminous bulb. Between the lure and the dorsal fin is a distinctive bulbous modified fin ray.

Males are free swimming when young but before they mature these small fishes (about a tenth the size of the female) attach themselves permanently to the hind body of the female and become parasitic. Their blood supply becomes continuous with that of the female and most of the internal organs degenerate: they become simply appendages to supply sperm when required.

Illustration by Dr Tony Ayling