Deep-sea fanfin anglerfish, Caulophryne jordani
There are at least 280 known species of anglerfish, all of which are very strange. Strangest of all are the five species of fanfin anglers.
Recent video footage from water off the Azores at a depth of 800m shows a female fanfin angler Caulophryne jordani drifting in the open water. As with all deep-sea anglers, she has a bioluminescent lure in front of her mouth to attract fish within range of her jaws. In addition, her fantastically long fin-rays seem to have either luminous or reflective patches on them, which might also attract prey. The exceptionally long fin-rays spread out around the fish, enabling her to detect any fish anywhere near her. More conventionally, the fish's lateral-line system picks up pressure changes in the water, created by moving objects. This is particularly well developed in fish in the dark and the fanfin angler is no exception, with very distinct pores visible.
The video of the fanfin angler also shows a male attached to her underside. In many anglerfish a male (rarely up to eight males) bites onto the female and becomes fused with her. Some anglerfish have normal males and females, but many go in for this bizarre form of reproduction. Some species are even more extreme; the males have extraordinarily large eyes, are not sexually mature and even lack digestive systems. If they fail to find a female quickly they died. If they are successful, they bite into the female. They then release enzymes that digest both the male's jaws and the part the female's body they are holding, resulting in them fusing together. The previously free-living male then absorbs nutrients and matures as an appendage of the female.
Photo: Rebikoff-Niggeler Foundation