In the animal kingdom, females are usually the "choosy" sex. Since they invest more in reproduction, they must set the bar for their mates high to avoid investing a lot of time and energy in a dud. African cichlids are no exception. In this species, females choose among males, then must raise the offspring all by themselves; picking a guy that’s a loser can be a pretty costly mistake for these ladies. A new study in PNAS shows that, after witnessing a fight between rival males, a female cichlid’s brain is highly responsive to whether her mate beats his opponent or gets creamed.
The researchers first determined which of two males a gravid (or ready-to-mate, in zoology jargon) female preferred by tallying up the amount of time she spent near each suitor. Then, they had the two males fight it out while the female looked on. Once the combat was over, the female was sacrificed to the science gods to examine what happened in her brain in response to the fight's outcome. The researchers wanted to know how the pattern of gene expression in her brain would differ if the male she chose won the fight versus if he lost.
When the male she'd chosen won the fight, expression of two immediate early genes (or IEGs) called c-fos and egr-1 was particularly high in the preoptical area and the ventromedial hypothalamus. These areas of the brain are well-known for being involved in reproductive activities. Basically, watching her chosen mate win the fight kicked her reproductive system into high gear to prepare her for spawning.
However, when her chosen male lost, gene expression changed in an entirely different part of the brain: the lateral septum. Interestingly, the nuclei in this area of the brain are responsible for regulating mood and modulating anxiety. The researchers believe that this neurological response may be how the female deals with the emotional fallout after she realizes that the male she had picked is actually a dud.
Here, using IEGs to monitor gene expression showed that, not only do females respond to purely visual information, their brains respond in a very specific way that depends on the kind of information gathered. From this research alone, it's not clear whether or not a female will adjust her future mate preferences after seeing her hottie lose, but this research is the first step in determining how the female brain processes social information about her mate.
PNAS, 2010. DOI: 10.1073/pnas.1010442107 (About DOIs).
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