Pheromones play an important role in modifying vertebrate behavior, especially during courtship rituals (Wyatt 2014). The courtship behavior within the urodele group often includes female exposure to secretions from the cloacal gland, as well as other scent glands. The first vertebrate proteinaceous pheromone discovered, the decapeptide sodefrin, is a female attracting pheromone secreted by the cloacal glands of male Cynops pyrrhogaster (Kikuyama et al. 1995). Other proteinaceous pheromones within the urodele group have been shown to elicit responses from females towards conspecific males (Yamamoto et al. 2000, Kikuyama et al. 2002, Houck et al. 2008). However, the presence and levels of expression of proteinaceous pheromones has yet to be identified within the family Ambystomatidae, which includes several important research models. Therefore, the objective of this research was to identify putative proteinaceous pheromones from male Ambystoma mexicanum, as well as their relative expression levels. The results indicate that A. mexicanum contains two different forms of sodefrin precursor-like factor (alpha and beta (Janssenswillen et al. 2015)), as well as a putative ortholog of plethodontid modulating factor. The beta form of sodefrin precursor-like factor was amongst the most highly expressed transcripts within the cloacal gland. The ortholog of plethodontid modulating factor was expressed at a level equivalent to the beta sodefrin precursor-like factor. The presence of these highly expressed proteinaceous pheromones may indicate that male A. mexicanum use several chemical cues to attract female conspecifics.
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