最新研究显示，印度孟买夜蛙具有一种非常独特的交配姿式，科学家将其描述为“背部跨坐”。

据英国每日邮报报道，之前科学家知道青蛙具有6种交配姿式，目前最新研究显示，事实上青蛙具有七种交配姿式。

科学家发现生活在印度西高止山脉的孟买夜蛙采取独特的交配方式——“背部跨坐”，这种特殊的交配姿式在全球6650种青蛙和蟾蜍物种是非常罕见的。它的学名为Nyctibatrachus humayuni，是印度西高止山脉生物多样热点区域的一种独特青蛙物种，它的皮肤褶皱布满斑纹，长着短而圆胖的肢体。

据悉，这是一种多样化远古青蛙物种，其历史可追溯至7000-8000万年前，目前在繁殖季节日落时分，可看到大量孟买夜蛙在溪流中鸣叫。印度德里大学和美国明尼苏达州大学科学家组建的一支研究小组发现孟买夜蛙独特的交配姿式，他们在2010-2012年之间季风季节观察了40个夜晚。

研究人员将这种交配方式命名为“背部跨坐”，因为雄蛙跨坐雌蛙背部，它的爪子抓着树叶或者树叶寻求支撑。这种现象不同寻常，因为多数雄蛙采取拥抱姿式与雌蛙交配。奇怪的是，在雄蛙离开雌蛙身体之前会将精液排在雌蛙背部，之后雌蛙排出卵子，从背部滴流下来的精液使卵子受精。因此，在孟买夜蛙产卵和受精过程中，它们并没有“直接接触”。

对于其它青蛙物种，雌蛙通常在与雄蛙抱合过程中产卵，同时，在这一过程雄性会排出精液使卵子受精。该研究负责人、印度德里大学SD Biju教授指出，这是一种非常独特的青蛙，具有前所未有的交配姿式，同时，这项研究将更好地理解无尾两栖生物(青蛙和蟾蜍)的进化生态性和行为特征。目前，这项最新研究报告发表在近期出版的《PeerJ》杂志上。

雌性孟买夜蛙为了展示“雌性吸引力”，在交配季节会发出鸣叫吸引交配者，这种现象在自然界仅存在于25种青蛙，通常情况下雄蛙会主动追求雌蛙进行交配。孟买夜蛙中也普遍存在着雄性竞争打斗现象，当一只雄蛙闯进另一只雄蛙的领地，一场争斗将不可避免地发生，直至侵入者被迫离开。同时，研究人员观察到一条蛇吞食了孟买夜蛙的卵，这是首次在印度发现的蛇吞蛙卵现象。（来源：腾讯科学 悠悠/编译）

A unique mating strategy without physical contact during fertilization in Bombay Night Frogs (Nyctibatrachus humayuni) with the description of a new form of amplexus and female call

Abstract  Anurans show the highest diversity in reproductive modes of all vertebrate taxa, with a variety of associated breeding behaviours. One striking feature of anuran reproduction is amplexus. During this process, in which the male clasps the female, both individuals’ cloacae are juxtaposed to ensure successful external fertilization. Several types of amplexus have evolved with the diversification of anurans, and secondary loss of amplexus has been reported in a few distantly related taxa. Within Nyctibatrachus, a genus endemic to the Western Ghats of India, normal axillary amplexus, a complete loss of amplexus, and intermediate forms of amplexus have all been suggested to occur, but many species remain unstudied. Here, we describe the reproductive behaviour of N. humayuni, including a new type of amplexus. The dorsal straddle, here defined as a loose form of contact in which the male sits on the dorsum of the female prior to oviposition but without clasping her, is previously unreported for anurans. When compared to known amplexus types, it most closely resembles the form of amplexus observed in Mantellinae. Furthermore, we prove that, opposed to the situation in most anurans, male semen release happens before egg deposition. We hypothesize that the male ejaculates on the female’s dorsum and that sperm subsequently runs from her back and hind legs before fertilizing the eggs. A second feature characterizing anuran breeding is the advertisement call, mostly produced solely by males. Despite recent descriptions of several new Nyctibatrachus species, few studies have explored their vocal repertoire. We describe both the male advertisement call and a female call for N. humayuni. The presence of a female call has not been reported within Nyctibatrachidae, and has been reported in less than 0.5% of anuran species. Altogether, our results highlight a striking diversity and several unique aspects of Nyctibatrachus breeding behaviour.

原文链接：https://peerj.com/articles/2117/