From Wildlife Extra:
New fish species has hooks on genitalia
Fishing hooks aren’t the only hooks found in east-central Mexican waters.
September 2012. A new species of freshwater fish, described by a North Carolina State University researcher, has several interesting – and perhaps cringe-inducing – characteristics, including a series of four hooks on the male genitalia. Females of the new species – the llanos mosquitofish, or Gambusia quadruncus – also have distinguishing characteristics, including a colourful anal spot. …
A paper describing the new species, which lives in a diversity hotspot and seemingly branched off from its closest relative more than one million years ago, appears in the Journal of Fish Biology.
See also here.