Pipefish, along with their cousins sea horses and sea dragons, defy convention in love and fertility. In a striking role reversal, fathers give birth instead of mothers.
During courtship, females pursue males with flashy ornaments or elaborate dances, and males tend to be choosy about which females’ eggs they’ll accept. Once pregnant, these gender-bending fathers invest heavily in their young, supplying embryos with nutrients and oxygen through a setup similar to the mammalian placenta.
But this investment may also be cruelly conditional, according to a new study in Proceedings of the Royal Society B. Studying pipefish, scientists found evidence that pregnant fathers spontaneously abort or divert fewer resources to their embryos when faced with the prospects of a superior mate — in this case, an exceptionally large female.
The researchers named their finding the “woman in red” effect, after the eponymous 1984 Gene Wilder film about a married man’s obsession with a woman in a red dress that becomes damaging to his family life.
The reported effect is an interesting instance of sexual conflict, which is ubiquitous among animals, said Sarah Flanagan, a pipefish expert at the University of Canterbury in New Zealand.
If you’re a romantic, you might think of mating as harmonious. But in nature, reproduction is more often a vicious power struggle between mothers and fathers with competing interests.
A maternal analogue to the “woman in red” effect occurs among mice. Males are willing to kill a female’s offspring, if they are unrelated to him, before mating with her.
In anticipation, a pregnant mother may terminate her pregnancy when exposed to a new male, rather than spending resources on doomed offspring.