Data from: On the effect specificity of accessory gland products transferred by the love-dart of land snails

Background: Sexual selection favours the evolution of male bioactive substances transferred during mating to enhance male reproductive success by affecting female physiology. These effects are mainly well documented for separate-sexed species. In simultaneous hermaphrodites, one of the most peculiar examples of transfer of such substances is via stabbing a so-called love-dart in land snails. This calcareous stylet delivers mucous products produced by accessory glands into the mate's haemolymph. In Cornu aspersum, this mucus temporarily causes two changes in the recipient. First, the spermatophore uptake into the spermatophore-receiving organ, called diverticulum, is probably favoured by contractions of this organ. Second, the amount of stored sperm increases by contractions of the copulatory canal, which close off the tract leading to the sperm digesting organ. However, it has yet to be determined whether these effects are similar across species, which would imply a common strategy of the dart in increasing male reproductive success. Results: We performed a cross-reactivity test to compare the in vitro response of the diverticulum and copulatory canal of C. aspersum (Helicidae) to its own and other species' mucus (seven helicids and one bradybaenid). We found that the contractions in the diverticulum were only induced by dart mucus of certain species, while the copulatory canal responded equally to all but one species' mucus tested. In addition, we report a newly-discovered effect causing the shortening of the diverticulum, which is also only caused by dart mucus of certain species. The advantage seems to be a distance reduction to the sperm storage organ. Conclusions: All these findings are the first to shed light on the evolution of the different functions of accessory gland products in dart-bearing species. These functions may be achieved via common physiological changes caused by the substances contained in the dart mucus, since the responses evoked were similar across species' mucus. Moreover, while these substances can act similarly in separate-sexed species as in simultaneous hermaphrodites, differences may occur in their evolution between the two sexual systems.研究背景：性选择会推动交配过程中传递的雄性生物活性物质的演化，这类物质通过影响雌性生理状态以提升雄性繁殖成功率。此类效应在雌雄异体物种中已有大量详实的研究记录。在同时雌雄同体物种中，这类物质传递最具代表性的特例之一，是陆生蜗牛通过刺入所谓的“恋矢（love-dart）”完成的：该钙质针状结构会将副腺分泌的黏液物质注入配偶的血淋巴（haemolymph）中。以散大蜗牛（Cornu aspersum）为例，其恋矢黏液会暂时使接收方发生两种变化：其一，被称为憩室（diverticulum）的精荚接收器官的收缩，可能会促进精荚被该器官摄取；其二，交配管的收缩会封闭通往精子消化器官的通道，从而提升储精量。不过目前仍不清楚这些效应在不同物种间是否具有普遍性，若存在普遍性，则意味着恋矢在提升雄性繁殖成功率方面存在共同的演化策略。 研究结果：本研究通过交叉反应试验（cross-reactivity test），比较了散大蜗牛（大蜗牛科Helicidae）的憩室与交配管在体外对自身及其他物种黏液的响应（受试物种涵盖7种大蜗牛科物种与1种巴蜗牛科物种）。结果显示，憩室的收缩仅由部分物种的恋矢黏液诱导，而交配管则对除一种受试物种外的所有黏液均产生了相似的响应。此外，本研究还首次报道了一种新发现的效应：恋矢黏液可诱导憩室缩短，该效应同样仅由部分物种的黏液触发，其潜在优势在于可缩短憩室与储精器官之间的距离。 研究结论：本研究的所有发现首次揭示了具恋矢物种副腺产物不同功能的演化机制。由于不同物种的黏液所引发的生理响应具有相似性，这些功能可能通过恋矢黏液中所含物质引发的共同生理变化得以实现。此外，尽管这类物质在雌雄异体物种与同时雌雄同体物种中可发挥相似的作用，但二者在两类生殖系统中的演化路径可能存在差异。