Departamento de Ecología Evolutiva, Museo Nacional de Ciencias Naturales, Consejo Superior de Investigaciones Científicas, José Gutiérrez Abascal 2, E-28006 Madrid, Spain.
Chem Senses. 2010 May;35(4):253-62. doi: 10.1093/chemse/bjq009. Epub 2010 Feb 22.
Pheromones of vertebrates are often a mixture of several chemicals with different properties and messages, and their production seems condition dependent. Thus, pheromones are a good, but little studied, example of multiple sexual signals. Femoral gland secretions of male rock lizards Iberolacerta cyreni contain steroids that may act as pheromones, but there are also many other lipids, such as oleic acid, whose allocation to secretions may be costly because it has to be diverted from body fat reserves. This suggests that oleic acid could also have some function in secretions. Chemical analyses showed that proportions of oleic acid in femoral secretions of males were positively related to body condition of males, suggesting that the oleic acid secreted may reflect the amount of body fat reserves of a male. Tongue-flick bioassays showed that females were able to detect by chemosensory cues alone differences in proportions of oleic acid in secretions of males. Scents of males with more oleic acid elicited stronger chemosensory responses by females. Further tests with chemical standards confirmed that females distinguished oleic acid, and changes in its concentration, from other chemicals that are naturally found in secretions of males. Moreover, choice trials of scent-marked substrates showed that females were more attracted to areas that were experimentally manipulated to increase the proportion of oleic acid in natural scent marks of males. We suggest that oleic acid in femoral secretions might be a reliable advertisement of a male's body condition, which females could use to select high-quality mates in conjunction with information provided by other chemicals. Alternatively, scent marks with more oleic acid might be simply more attractive to females if chemosensory responses of females to scent of males were originated by a preexisting sensory bias for food chemicals such as the oleic acid. Nevertheless, this sensory trap might have evolved into an honest signal because the elaboration of the signal seems differentially costly for males with different body conditions.
脊椎动物的信息素通常是几种具有不同性质和信息的化学物质的混合物，其产生似乎依赖于条件。因此，信息素是一个很好的例子，但研究较少，它是多种性信号的一个例子。雄性岩蜥 Iberolacerta cyreni 的股腺分泌物含有类固醇，可能作为信息素起作用，但也有许多其他脂质，如油酸，其分配到分泌物中可能是昂贵的，因为它必须从体脂肪储备中转移。这表明油酸在分泌物中也可能具有某些功能。化学分析表明，雄性股腺分泌物中油酸的比例与雄性的身体状况呈正相关，这表明分泌的油酸可能反映了雄性体脂肪储备的数量。舌舔生物测定表明，雌性能够仅凭化学感觉线索单独检测雄性分泌物中油酸比例的差异。油酸含量较高的雄性的气味会引起雌性更强的化学感觉反应。用化学标准品进行的进一步测试证实，雌性能够区分油酸及其浓度与雄性分泌物中自然存在的其他化学物质。此外，对有气味的基质进行选择试验表明，雌性更容易被实验操纵以增加雄性自然气味标记中油酸比例的区域所吸引。我们认为，股腺分泌物中的油酸可能是雄性身体状况的可靠标志，雌性可以结合其他化学物质提供的信息，利用它来选择高质量的配偶。或者，如果雌性对雄性气味的化学感觉反应是由对食物化学物质（如油酸）的预先存在的感官偏见引起的，那么油酸含量较高的气味标记可能对雌性更有吸引力。然而，这种感觉陷阱可能已经进化成一种诚实的信号，因为信号的产生对身体状况不同的雄性来说似乎是有差异的成本。
