Like something out of a sci-fi movie, the anglerfish comprises more than 200 species of rather angry looking fish. Most of these species in the dark depths of the Atlantic and Antarctic oceans, to depths of over 3000 feet. Despite being some of the most well-known deep sea inhabitants, scientists have rarely seen them in their natural environments. Anglerfish are named for their characteristic mode of predation. Its elongated dorsal spine supports a biolumiescing photophore which it was back and forth to lure prey within striking distance in the deep dark oceans
Another characteristic of some group members is the very distinct sexual dimorphism and sexual symbiosis seen in the Ceratioidei suborder. A new video captured from the waters around Portugal’s Azores islands provides stunning evidence of these characteristic features. The video shows a fist-sized female fanfin angler, Caulophryne jordani, with her bioluminescent lights and elongated whisker-like filaments and fin rays projecting and enveloping her body. However, looking more closely she also has a mate, a dwarf male fused to her underside who is essentially a permanent provider of sperm.
The video was captured via a submersible at a depth of 800 meters by deep-sea explorers Kirsten and Joachim Jakobsen. Upon returning to the surface the explorers sent the video to Ted Pietsch, a deep-sea fish researcher at the University of Washington in Seattle. Despite identifying many species, only a few videos exist and this video is the first to show a sexually united pair. “So you can see how rare and important this discovery is,” Pietsch says. “It was really a shocker for me.”
Apart from the esca, the bioluminescent organ, the filaments and fin rays also appeared to produce light at their tips and at intervals along their length. This feature is also something that has never been witnessed. The expert Pietsch hypothesized that the light is also bioluminescent produced within the animal itself. However, Pietsch is unsure whether the structures are reflecting light produced by the submersible.
The dwarf male, usually many orders of magnitude small than the female, forms a pair bond with the female. The male bites the her, eventually fusing with the female’s tissue and receives sustenance through her blood stream like a parasite.
For me info on this fascinating group of species see the following web links:
http://www.sciencemag.org/news/2018/03/exclusive-i-ve-never-seen-anything-it-video-mating-deep-sea-anglerfish-stuns-biologists
https://www.nationalgeographic.com/animals/fish/group/anglerfish/
