Staying in the red: Mating preferences for novel coloration in zebrafish (Danio rerio)

Background/Question/Methods

Studies of mating preferences contribute to our understanding of the evolution of secondary sexual traits in males.  How females respond to novel male characteristics may lend insight into these mating preferences and subsequent mate choice patterns.  Studies have shown that females can have preferences for male traits not exhibited by conspecific males.  I investigated this phenomenon using normal and genetically modified (red GloFish^TM) zebrafish (Danio rerio).  Using females from a mixed-phenotype rearing environment, I assessed female preference for normal versus “novel” (i.e. GloFish^TM) males using an association testing protocol.  The test area was partitioned into three aquaria lined end to end: a central aquarium containing the female and two outer aquaria (one for each male).  The female aquarium consisted of a choice zone near each male and a central, neutral zone.  Percent time females spent in male choice zones was recorded and a male was designated as “preferred” if the female spent at least 60% of her total choice time in his choice zone.  In some species, females use male phenotypes from their early social environment as a template for an attractive mate.  To test the influence of this ontogenetic learning, I tested females that were raised in the following treatment groups: nine GloFish^TM:three normal, three GloFish^TM:nine normal, 12 normal, and 12 GloFish^TM using the identical protocol.

Results/Conclusions

Both normal and GloFish^TM females overwhelmingly preferred to associate with GloFish^TM males.  Preliminary data from the ontogenetic learning experiment suggest females across all treatment groups prefer GloFish^TM males, but association times with GloFish^TM males are much lower compared to females from the original experiment.  To determine if female perception of male color influenced female association times, I will calculate the chromatic contrast of each male phenotype against the white test arena background.  In conclusion, female zebrafish prefer a novel trait in males; however, additional work will elucidate the evolutionary and/or proximate causes underlying this preference.