The Fanfin Seadevil deep-sea anglerfish has been caught mating on camera for the first time. This beauty is an “apparently gravid” – pregnant, or egg-laden – female with a sexually parasitic dwarf male attached to her belly. She’s about 16 centimetres in length, linked to a three centimetre male. To reproduce, a male anglerfish has to locate a female in the deep sea and attach himself to her, leading to a permanent fusion of tissues and the interconnection of their two circulatory systems. In short: this guy’s hooked.
Kirsten and Joachim Jakobsen took this shot on their LULA1000 submersible vehicle at a depth of 800 metres “in a zone characterized by steep, partially vertical walls" just off the south slope of São Jorge Island, Azores. The vehicle is able to take quality photos and videos at depths of up to 1,000 metres. “It's basically a propelled deep-sea camera with the camera operators sitting inside the 1.40m diameter acrylic lens,” say the Jakobsens, and has been in operation since 2013. Usually they use it to perform seabed mapping, for the collection of oceanographic data and to film for nature documentaries including Blue Planet. The project was supported by the Rebikoff-Niggeler Foundation, a science foundation operating in Portugal’s Azores Archipelago.
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According to Theodore W. Pietsch at the University of Washington, this unusual anglerfish is a Caulophryne jordani, more commonly known as the Fanfin Seadevil. The long rays you can see emanating from the female Fanfin Seadevil’s body are “innervated rays of the dorsal and anal fins, unconnected by membrane”, which act like a network of sensory antennae – something akin to cat whiskers. This array effectively creates a sphere around the fish to monitor nearby predators or prey. This appearance and behaviour have never been documented before, Pietsch says, and members of this genus of anglerfish “are strikingly different from all other anglers in having those elongate fin-rays, plus we've never seen anything like that elaborate ‘light-show’” along of the fish's pectoral and caudal rays.
This is a very rare species of anglerfish, known only from 14 female specimens. Males of this species had never seen before this image. This also is first observation of a sexually parasitised female in its own habitat out of any of the 160 species of anglerfish currently recognised. “I've been studying these fishes for fifty years and I've never seen nor have I ever dreamed of anything like this,” says Pietsch.