Data from: An androgenic endocrine disruptor alters male mating behaviour in the guppy (Poecilia reticulata)

Hormonally active chemical pollution threatens human and wildlife
populations globally. However, despite the well-established capacity of
endocrine-disrupting chemicals (EDCs) to alter reproductive traits,
relatively few studies have examined the impacts of EDCs on mechanisms of
sexual selection. This study investigated the effects of short-term
exposure to an environmentally realistic level of 17β-trenbolone—a potent
anabolic steroid used in livestock production worldwide—on male mate
preference, reproductive behaviour and morphology in the guppy (Poecilia
reticulata). Male guppies prefer to mate with larger females because such
females are generally more fecund. Hence, males gain direct fitness
benefits by being choosy. Here, we found no significant effect of
17β-trenbolone exposure on male courting behaviour, with both unexposed
and exposed males courting larger females more often. However, exposure to
17β-trenbolone significantly altered the amount of coercive copulatory
behaviour (‘sneak’ matings) performed. Specifically, while both unexposed
and exposed males demonstrated a preference for larger females by
conducting more sneaking attempts towards these females, exposed males
carried out a greater number of sneaks towards large females than did
unexposed males. Further, exposure resulted in increased male condition
index (i.e., mass relative to length). Together, our results show for the
first time that 17β-trenbolone can alter reproductive behaviour and
morphology in male fish at concentrations as low as 4 ng/L, highlighting
the potential for disruption of reproductive processes in wildlife exposed
to this potent agricultural contaminant.

激素活性化学污染对全球人类和野生动物种群构成威胁。然而，尽管内分泌干扰物（EDCs）改变生殖性状的能力已得到充分证实，但研究EDCs对性选择机制影响的文献相对较少。本研究探讨了短期暴露于环境真实浓度的17β-群勃龙（一种在全球畜牧业中使用的强效合成代谢类固醇）对孔雀鱼（Poecilia reticulata）雄性配偶偏好、繁殖行为及形态学特征的影响。

雄性孔雀鱼偏好与体型较大的雌鱼交配，因为这类雌鱼通常繁殖力更强。因此，雄性通过选择性交配可获得直接的适合度收益。

研究发现，暴露于17β-群勃龙对雄性求偶行为无显著影响——未暴露组与暴露组雄性均更频繁地向体型较大的雌鱼求偶。然而，该化学物质暴露显著改变了雄性的强迫交配行为（‘偷袭交配’）频次。具体而言，尽管两组雄性均通过向体型较大雌鱼发起更多偷袭交配来表现偏好，但暴露组雄性对大型雌鱼的偷袭交配次数显著多于未暴露组。

此外，暴露还导致雄性状态指数（即体重与体长的比值）升高。综上，本研究首次证实，浓度低至4纳克/升的17β-群勃龙即可改变雄性鱼类的繁殖行为与形态特征，凸显了这种强效农业污染物对野生动物繁殖过程的潜在干扰风险。