Aug 30

Bizarre Animal of the Week: Deep-Sea Anglerfish

The deep-sea anglerfish never looks happy. I can understand why. You’d be pretty cranky all the time, too, if you were that profoundly ugly and lived a few miles down in the lonely, completely lightless and desolate habitat that is the great ocean abyss. Life can’t get much bleaker. Or can it?

Deep sea Angler fish

Photo: David Shale

Well, for a male anglerfish, it can. The picture above is of the female deep-sea anglerfish, a creature that seems to have jumped straight out of a science-fiction movie. Like many of her kind, her huge mouth takes up the majority of the front half of the fish, and the long, backward-facing teeth make it so that the mouth cannot even be shut properly. Then there is that strange fleshy growth protruding from her head, actually a lure that ends in a bulb packed with bioluminescent bacteria. Small fish are drawn to the light in the pitch blackness like moths are to a flame, and are easily snapped up by the angler.

This, however, is a male…

Photo: Mudfooted

He’s miniscule, many times smaller than the female, and much less intimidating. He doesn’t even possess a lure and eats only whatever small fragments of edible matter he can find. Then, when he reaches sexual maturity, things get worse. His digestive system disintegrates and his sole purpose in life is now not to feed but to find a mate in the perpetual gloom. He has an extremely sensitive sense of smell and when he finally detects the pheromones given off by the female, he hunts her down and becomes rather clingy, in more ways than one. He bites onto her body and hangs on. He will never let go of her again.

The male anglerfish releases an enzyme that digests the skin of his own mouth and her body, fusing the pair down to the blood vessel level. This is especially important to the male since he has no digestive system to speak of and so he relies entirely on the much larger female to sustain him with nourishment from her own body. In return for sustenance, the male becomes the female’s permanent sex slave. In the picture below, you can see the tiny male attached to the top of the female’s head.


Photo: David Paul/Mark Norman

Then, as if things couldn’t get more bizarre, the male begins to disappear. His body literally atrophies to almost nothing; his scales, bones, muscle and organs merge into the body of the female. After a few weeks, the male has all but gone, leaving behind just a pair of testes hanging from the female’s side like an unpleasant tumour. She uses these to supply her with sperm whenever she wishes to reproduce. A single female deep-sea anglerfish can have dozens of testicles dangling from them, the last degenerate remains of many eager males.

This extreme sexual dimorphism and odd reproductive strategy is all down to the difficulty in finding a mate at the bottom of the sea. It is vital that when the male and female of a species finally find each other that they stick together – and in the case of the deep-sea anglerfish, they literally do just that. It also means that whenever the female is ready to spawn, she always has a supply of sperm already available.

It’s clear that the female deep-sea anglerfish not only wears the trousers in this relationship, but she is also the obvious breadwinner. The male, meanwhile, has been completely screwed over. His entire existence has been downgraded until now he has become nothing more than a swimming pair of testicles. That’s about as bleak as life can get.

3 pings

  1. […] they play. It’s a topic we’ve covered before on this blog – consider the tiny, parasitic male anglerfish, for example – but no animal exhibits the striking differences between the sexes more […]

  2. […] already talked about anglerfish at Extraordinary Animals before (see here if you want to refresh your memory), but now it’s time to delve into some of the weirder […]

  3. […] Sources: Male Anglerfish, Fun Fact, Oceana  […]

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