How sexual harassment affects the next generation

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Sexual harassment exacts a toll on the offspring of female guppies, according to a study to be published in a forthcoming issue of the journal Evolution.

Clelia Gasparini, Alessandro Devigili and Andrea Pilastro examined the consequences of the sexual harassment of female guppies for their descendants by experimentally manipulating the level of sexual harassment and mating rate in two groups of female guppies.

The authors then investigated the effects of sexual harassment on female fitness by measuring the body growth, survival and lifetime fecundity of these two groups of females, along with the body size and swimming performance of their offspring at birth.

They then further explored the long-lasting effects of sexual harassment in the next generation by raising to maturity the offspring that were born about four months after the beginning of the experiment, measuring several traits associated with reproductive success, such as survival and body size (in daughters and sons), and gonopodium length, ejaculate quality, sexual behaviour and sexual attractiveness (in sons only).

Using descendants of wild-caught fish from Trinidad, the authors divided 62 females into two groups and artificially inseminated them. Each pregnant female was then housed individually in tanks, and the experiment allowed to begin after they delivered their first broods and were performed at every reproductive cycle throughout each female’s lifetime.

In the first group, designated as the low sexual harassment group, three male guppies were allowed to simultaneously interact with the female for one day during her receptive period (24 hours following birth).

In the second group, designated as the high sexual harassment group, the interaction time of the three male guppies was increased to eight days.

Not surprisingly, the authors found that the females in the high sexual harassment group experienced significantly more intense sexual harassment than their counterparts in the other group.

What was surprising was the fact that the overall fitness of the females was not adversely impacted by increased sexual harassment.

However, the same could not be said of the offspring. Although the level of sexual harassment produced no significant effects on offspring size and performance (schooling and escape ability) at birth, the authors found that females that were highly sexually harassed produced daughters with smaller bodies and sons with shorter gonopodia, which were less attractive to females and less successful in coercive matings than their counterparts in the other group.

The results of the study suggest that sexual harassment and elevated mating rate can negatively impact the fitness of the next generation and may have more profound evolutionary consequences than currently thought.

For more information, see the paper: Gasparini, C, A Devigili and A Pilastro (2011) Cross-generational effects of sexual harassment on female fitness in the guppy. Evolution doi:10.1111/j.1558-5646.2011.01455.x

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