Sexual parasitism in anglerfish

Before I take off, I wanted to highlight one more marvel of evolution: the phenomenon of sexual parasitism in anglerfish.  There are many species of these deep-sea fish, who make their living as predators in the abyssal depths.  Because the population density is low, when a male finds a female his best strategy (apparently) is to fuse his tissues with hers, becoming in effect a permanently parasitic sack of gonads, whose only function is to fertilize the female (no anthropomorphizing, please!).  Sometimes more than one male attaches to a female.  Here are some photos.


The phantom anglerfish, Haplophryne mollis, with male attached on bottom.


Photocorynus spiniceps, an anglerfish from Sumatra. This female is 46 mm long (1.8 inches). Attached to her is a 6.2 mm male (about 0.25 inches), which may be the smallest sexually mature vertebrate known. Below is an enlarged photo of the male.



  1. Rizwan
    Posted November 8, 2009 at 4:32 pm | Permalink

    Very interesting, happened to come to this site while reading up on adaptations of organisms that inhabit the deep seas.

  2. Ronaldo Santos
    Posted February 26, 2010 at 10:49 am | Permalink

    how can you say it is “marvel of evolution”?

  3. Robert Z
    Posted April 15, 2010 at 3:23 pm | Permalink

    How could this reproductive strategy evolve, in a stepwise fashion, from any other known form of reproduction in fishes?

  4. thh1859
    Posted January 2, 2013 at 9:36 am | Permalink

    Quite a few barnacle species have dwarf males, as Darwin noticed. There are several theories on the evolution of dwarf males mentioned in this paper.

    {How would I turn this into a link here?]

    • thh1859
      Posted January 2, 2013 at 9:37 am | Permalink

      Ah! It’s automatic.

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