Emerson S B, Boyd S K
Department of Biology, University of Utah, Salt Lake City, Utah 84112, USA.
Brain Behav Evol. 1999;53(4):187-97. doi: 10.1159/000006594.
Vocalization behaviors of anuran amphibians are universally sexually dimorphic. Usually, only male frogs give an advertisement call, while female frog calls are limited to a soft and simple release call which is specifically suppressed at mating. In a very few species, however, female frogs also give mating vocalizations. We examined possible mechanisms for control of this rare heterotypical behavior. At the peripheral level, most differences in temporal and spectral characteristics between female mating calls and the calls of conspecific males related directly to sexual dimorphisms in laryngeal and oblique muscle morphology. At the neural and hormonal level, we first developed an integrated model for control of vocalizations, based primarily on male frog data. When this model is applied to females, female mating vocalizations were most similar to male advertisement calls, rather than being modified release calls. Females may have conscripted preexisting androgen-sensitive neural pathways typically used only by males but present in both sexes. Female mating calls have been heard only during courtship and amplexus. Androgen levels in females at this time are significantly higher than even those levels in males. Because this situation is common in frogs, female mating vocalizations likely evolved independently multiple times. Character optimization suggests that mate location is the most common biological role for female mate calling, but the particular aspects of reproductive biology vary widely across species.
无尾两栖动物的发声行为普遍存在性别差异。通常，只有雄蛙会发出求偶叫声，而雌蛙的叫声仅限于一种轻柔简单的释放叫声，在交配时这种叫声会受到特别抑制。然而，在极少数物种中，雌蛙也会发出交配叫声。我们研究了控制这种罕见异型行为的可能机制。在外周水平上，雌蛙交配叫声与同种雄蛙叫声在时间和频谱特征上的大多数差异直接与喉部和斜肌形态的性别二态性有关。在神经和激素水平上，我们首先主要基于雄蛙数据建立了一个控制发声的综合模型。当将这个模型应用于雌蛙时，雌蛙的交配叫声与雄蛙的求偶叫声最为相似，而不是经过修饰的释放叫声。雌蛙可能征用了通常仅雄蛙使用但两性都存在的预先存在的雄激素敏感神经通路。雌蛙的交配叫声只在求偶和抱对期间被听到。此时雌蛙体内的雄激素水平甚至显著高于雄蛙。因为这种情况在蛙类中很常见，所以雌蛙的交配叫声可能多次独立进化。特征优化表明，配偶定位是雌蛙发出交配叫声最常见的生物学作用，但生殖生物学的具体方面在不同物种间差异很大。
