A newly-released video, captured in the waters around Portugal’s Azores islands, shows a pair of deep-sea anglerfish called the fanfin angler (Caulophryne jordani) mating: a fearsome-looking female and her parasitically attached mate drift almost helplessly, salvaging precious energy in their dark, food-scarce environment.
A pair of fanfin anglers (Caulophryne jordani). Image credit: Rebikoff-Niggeler Foundation.
Deep-sea anglerfish are marine bony fish of the teleost order Lophiiformes.
They are found in all oceans around the world, yet the roughly 160 known species are extremely rare.
They lure their prey in the inky-black ocean darkness at depths between 980 and 16,400 feet (300-5,000 m) using a bioluminescent fishing apparatus placed on the tip of the snout — hence the ‘angler’ in their common name.
Their enormous, toothy mouth and expandable stomach enable them to capture and devour prey larger than themselves in a single instantaneous gulp.
Deep-sea anglerfish males are a fraction of the size of the females — in the most extreme cases, females may be more than 60 times the length and about a half-a-million times as heavy as the males.
The males don’t have a luring apparatus; instead, most have large, well-developed eyes and huge nostrils, which help them home in on a species-specific chemical attractant emitted by the females.
The pair of fanfin anglers was filmed by marine biologists Kirsten and Joachim Jakobsen aboard the LULA1000, a submersible operated by the marine science-focused Rebikoff-Niggeler Foundation.
“This is a unique and never-before-seen thing. It’s so wonderful to have a clear window on something only imagined before this,” said Professor Ted Pietsch, from the University of Washington and the Burke Museum of Natural History and Culture.
For some 25 minutes, the female fanfin angler was observed to float slowly and gracefully, rolling in the current, head down and head up, through the pitch-black water at a depth of about 2,600 feet (800 m).
She swept her long whisker-like fin-rays back and forth, with pinpoints of light emanating at intervals along the length of each ray — the soft, spine-like structure that supports the fins. Hard to see at first glance was a tiny male, hanging from her belly.
“Once a male finds a female, a seemingly impossible task in the vast open space of the deep sea, he bites onto her body, the tissues and circulatory systems of the two fuse, and he is fed by nutrients received through her blood,” the biologists explained.
“The male becomes a ‘sexual parasite,’ hanging on for the rest of his life and unable to free himself, fertilizing the eggs produced by the female.”
“The male completely loses his individuality and the couple becomes a single functioning organism.”
“Video footage of this kind allows us to see these animals behaving in the wild, something otherwise impossible,” Professor Pietsch said.
