凹耳蛙声通讯中非线性现象的功能及两性间近距离通讯

Nonlinear phenomena (NLP) can be found in many animals’ vocalizations. Whereas we have a good understanding of the generating mechanism of NLP, the functional significance of NLP in sound communication remains unclear. The vocalizations of female/male concave-eared torrent frogs are highly unusual as they contain abundant NLP, yet what are the functions of NLP in species reproduction and individual recognition? Next, given that both sexes are now known to vocalize during the reproductive season and that both the male’s advertisement call and the female’s courtship call elicits phonotaxis for the opposite sex, which sex then performs the mate choice, and how do female and male interact behaviorally and acoustically in order to form amplexus? Finally, compared to males, females possess much larger body size and more massive vocal folds, and yet the fundamental frequencies of their vocalizations are essentially identical – this relationship between the size of vocal folds and sound frequency violates common law in physics. The goals of this proposed research are to address these issues above, specifically to: 1) investigate whether the occurrence of NLP in male advertisement calls increases as the evening chorus progresses, especially when females emerge during the chorus, 2) investigate the significance of NLP in male’s neighbor-stranger discrimination, 3) investigate the importance of NLP to phonotaxis in concave-eared torrent frogs across sex, 4) investigate how males and females communicate in short ranges, and to gain insights into male-female interactions leading to the formation of amplexus, 5) investigate the sound production mechanism in females to resolve the paradox of their high-frequency calls despite having massive body size and vocal folds. Results of these studies shall significantly increase our understanding of the function of NLP in sound communication in concave-eared torrent frogs (an extraordinary anuran species in nature) and of the roles of males and females in sexual communication in this remarkable species.

许多动物的声音中都含有非线性现象（NLP），人们对NLP产生机制已有较好认识，但对其在声通讯中的功能还不甚了解。雌雄凹耳蛙声音均包含丰富的NLP,那么NLP在该蛙繁殖和个体识别中有何作用？雌雄凹耳蛙繁殖季节都可发声，雄性广告音和雌性求偶音都会引起异性趋声性，两性中谁来完成交配选择及如何进行行为和声音交流以实现抱对？此外，和雄蛙相比，雌蛙体长更长声带更大，其叫声的基础频率却和雄蛙同样高，这有悖于发声器官大小和发声频率成反比的常理。为此，本项目将开展以下研究: 1）雄蛙广告音中NLP的发生是否会随着合唱的发展特别是雌蛙的出现而增加；2）NLP在雄性的邻居蛙-陌生蛙识别中的作用；3）NLP在雌雄凹耳蛙趋声性中的重要性；4）雌雄凹耳蛙近距离通讯及其抱对过程；5）雌性凹耳蛙高音调的发声机制。研究结果将加深对NLP在凹耳蛙声通讯中的功能及两性在性通讯中作用的理解。

许多动物的叫声中都包含非线性发声现象（Nonlinear phenomena, NLP），目前人们对NLP在声通讯中的功能了解还十分有限。雌/雄凹耳蛙声音均包含丰富的NLP，然而NLP在凹耳蛙求偶合唱过程中的变化，NLP对凹耳蛙个体间交流和繁殖的影响等一直未见报道。本项目的主要研究内容包括：1）雄性凹耳蛙不同合唱时期声音中 NLP 含量的变化；2）NLP 对雌雄性凹耳蛙趋声反应的影响；3）雄性凹耳蛙的邻居蛙是否会对陌生蛙 NLP 声音反应更强烈，例如是否具有更短的应答反应时间，是否会被诱导发出更多的应答音；4）雌/雄凹耳蛙的近距离通讯以及抱对过程的决定者；5）雌性凹耳蛙声带控制频率的部位及其结构上的特异性。研究结果表明：1）雄性凹耳蛙不同合唱期会采取不同的发声策略，在性选择压力较小的低潮期，雄性凹耳蛙通过提高鸣声中的NLP含量，扩大声音传播距离，增大声音的不可预测性，以更好吸引雌性；在性选择压力较大的高潮期，雄蛙通过提高鸣叫率使得个体鸣声更加突出，从而提高抱对的成功率；2）雌性凹耳蛙鸣声中的NLP半谐波组分会引起雄性更多的单音节应答音，频率跳跃组分会引起雄蛙更多的断奏应答音；3）凹耳蛙鸣声中的NLP能够增强其声音的不可预测性，引起雄性陌生蛙产生更多的应答音；4）雌雄凹耳蛙近距离交流过程中涉及多模态信号，例如视觉信号（眨眼、低头、腹部膨胀、脚趾震动、背转向雄蛙）和声信号。繁殖期雌性凹耳蛙交流信号中视觉信号所占的比例高于声信号。另外，通过视觉回放实验首次证明眨眼可能是除灵长类之外，在两栖类中首次发现的特殊种间社会信号。最后视觉回放实验的结果也证明雌性凹耳蛙是抱对过程的决定者；5）受疫情影响，未能赴国外合作实验室开展凹耳蛙声带结构和特异性等研究。