Is that a guppy in your pocket, or are you just happy to see me?
Male guppies exposed to high doses of a common SSRI over multiple generations ended up with bigger sex organs, according to a new study out of Monash University.
The five-year investigation looked at a population of wild-caught guppies exposed to varying levels of SSRI fluoxetine (Prozac) to explore the effect of pharmaceutical pollution on aquatic ecosystems.
Male guppies, which have heightened sensitivity to environmental shifts, were selected as the ideal pool of participants (pun very much intended).
Over 15 generations, guppies exposed to high concentrations of fluoxetine had improved body condition compared to control group males, while those exposed to lower fluoxetine doses deteriorated in condition.
“Body condition is an important mediator of sexual selection in adult guppies for male-male competition, courtship behaviour, and coercive copulation with females,” the authors wrote in the Journal of Animal Ecology.
“Therefore, the dose-dependent effects observed here on body condition may lead to varying fitness outcomes in male guppies exposed to different polluted environments.”
The fish exposed to fluoxetine also had larger gonopodiums, which are essentially modified anal fins which act like a penis, but reduced sperm velocity.
“Since longer gonopodium is beneficial for coercive mating in guppies and fluoxetine exposure can increase male coercive mating behaviour, selection for longer gonopodia can favour males to gain higher pre-copulatory mating success,” the authors said.
“This should be especially important for males living in polluted waters if the exposure to the pollutant has negative effects on male post-copulatory traits – i.e., it compromises the competitiveness of sperm and reduces fertilisation success.”
The key takeaway, though, isn’t that male guppies are horny little creeps when exposed to SSRI pollution (at least according to the researchers).
Instead, it’s that pharmaceutical pollution can alter the fundamental trade-offs between behaviour, life history and reproduction in animals.
Please refrain from sending your gonopodium pics to Penny@medicalrepublic.com.au.
