Unique video of anglerfish mating in the wild

This is a short but stunning video of a rarely-seen fish, the fanfin anglerfish Caulophryne jordani, one of 160 species of deep-sea anglerfish.  It shows a bizarre female with her huge mouth and onboard lights to attract prey (and mates) in the dark, as well as the tiny male, who, because population density is low, fuses to the female’s body and, losing its head, becomes part of her for life—a parasitic bag of sperm.

You can read more about this video at Science; I’ll give one excerpt:

The video was captured at a depth of 800 meters by deep-sea explorers Kirsten and Joachim Jakobsen in a submersible. The husband and wife team was nearing the end of a grueling 5-hour dive along a steep deep-sea wall on the south side of São Jorge Island, when “something with a funny form” caught their eye, Kirsten Jakobsen says. Aborting their plan to surface, the filmmakers followed the strange creature around for 25 minutes, capturing its movements through the submersible’s 1.4-meter-wide window. It was exciting, but also challenging to maneuver the craft to get the best images because the female was only about 16 centimeters long, she says.

After surfacing, the duo sent the video to Pietsch, who identified the species as Caulophryne jordani, known as the fanfin angler. He was entranced by the species’s “gracefulness,” especially the way those whiskerlike structures—called filaments and fin rays—enveloped the animal. “Any prey item touching one of those would cause the angler to turn and gobble up that particular animal,” he says. “They can’t afford to let a meal go by because there’s so little to eat down there.” The video was captured in August 2016, but this is the first time it’s been released to the public.

C. jordani’s light show was also a stunner. Like other deep-sea anglerfish, the female has a bioluminescent, lurelike appendage that drifts in front of her head to attract prey. But in the video, the filaments and fin rays also appear to emit light at their tips and at intervals along their length—something that’s never been seen before. Pietsch suspects that the light is bioluminescent—meaning, it’s produced within the animal itself—but he notes that it’s hard to know whether the structures are reflecting light from the submersible or are actually glowing.

The tiny male is also a key part of the discovery. Like many other species of anglerfish, C. jordani forms a permanent pair bond—once a male finds a mate, he bites into her, eventually fusing with her tissue and gaining sustenance through her blood stream. Scientists have known about this bizarre reproductive strategy because they’ve seen dead males latched onto dead females, but people have never seen it in the wild—until now.

Bruce Robison, a deep-sea ecologist at the Monterey Bay Aquarium Research Institute in Moss Landing, California, was impressed with how flexible the male was despite its solid attachment, seemingly moving around in any direction he wished. “There’s no way I would have ever guessed that from a [museum] specimen.”


I wonder if more than one male can fuse to a female at once, if she has any say in the process or can’t give affirmative consent, or if she can reject an unsuitable male. Who knows? In some ways the deep sea is as much a mystery, or even more of one, than bodies like Mars and the Moon.


  1. ThyroidPlanet
    Posted December 26, 2018 at 2:17 pm | Permalink


  2. Posted December 26, 2018 at 2:30 pm | Permalink

    What amazing video!

  3. Posted December 26, 2018 at 2:32 pm | Permalink

    Fantastic video! Strangely beautiful and ugly at the same time.

    • Ken Kukec
      Posted December 26, 2018 at 3:17 pm | Permalink

      Jolie laide is the French term for that, I think (though I understand the French don’t actually use it much).

  4. JezGrove
    Posted December 26, 2018 at 2:54 pm | Permalink

    Much more mysterious than anything we’re likely to find on the Moon or Mars – though those discoveries are valuable too.

  5. Posted December 26, 2018 at 2:55 pm | Permalink

    Very cool! One wonders how an approaching male avoids being considered as prey.

  6. CAS
    Posted December 26, 2018 at 3:01 pm | Permalink

    Neat video!

  7. rickflick
    Posted December 26, 2018 at 4:30 pm | Permalink

    Very cool. I note that the female’s eyes are quite small. Not what you’d expect from a fish living in those gloomy depths. Perhaps it’s vision is limited to close range – the distance to the bioluminescent lure.

  8. Matthew North
    Posted December 26, 2018 at 5:12 pm | Permalink


    Yes, multiple males can fuse with a female.

  9. Matthew North
    Posted December 26, 2018 at 5:14 pm | Permalink


    ^ Whoops, meant this.

    • Nicolaas Stempels
      Posted December 26, 2018 at 10:20 pm | Permalink

      I think the question was several males at once, at the same time, but I guess yes

  10. Matthew North
    Posted December 26, 2018 at 5:37 pm | Permalink

    The known record is eight males fused to one female!!

    That makes you wonder which of the multiple male’s sperm gets to fertilize the female. Sperm competition in nature is ubiquitous. It’s so hard to study these fish that it’s hard to foresee an answer any time soon.

  11. Posted December 28, 2018 at 1:40 pm | Permalink

    Stunning video! I thought that the anglerfish has just one light, the one hanging above the head.

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