Proteins salamander pheromone

The production of a female-influencing secretion from the chin gland of male Plethodontid salamander (P. jordani) points to a similar extension of function by the acquisition of female olfactory sensitivity to an intercellular signal protein. Female receptivity is enhanced by a male cytokine-like compound of the interleukin-6 family, in its released form. Rollman et al. (1999) note that pheromonal activity is a previously unrecognised function for cytokines. 

In the plethodontid salamander D. ocoee, courtship duration was reduced for male-female pairs in which the female received a protein signal from the 20-25 kDa fraction of the male courtship pheromone. We interpret this reduction in courtship duration as an increase in receptivity for females receiving the pheromone. 

The delivery of male courtship pheromones is widespread among plethodontid salamanders (Houck and Arnold 2003), and other courtship pheromones are being discovered for this group (Houck, Palmer, Watts, Arnold, Feldhoff and Feldhoff 2007). The mode by which these pheromones are transferred to the female apparently has been modified from delivery via diffusion into the circulatory system to delivery that directly stimulates vomeronasal receptors (Fig. 20.1 Houck and Sever 1994 Watts et al. 2004 Palmer et al. 2005 Palmer et al. 2007). The behavior patterns and morphologies associated with these two delivery modes often remain static for millions of years. In contrast, evolution at the level of pheromone signals is apparently an incessant process that continuously alters the protein sequence and composition of pheromones both within and among species (Watts et al. 2004 Palmer et al. 2005 Palmer et al. 2007). 

Another salamander courtship pheromone, identified in 1999, is a protein. During courtship, males of the Appalachian woodland salamander, Plethodon jordani, (Plethodontidae), a terrestrial species, actively deliver a pheromone to the female. In the mating season, males develop a mental gland, located... 

Figure 2. Analysis of courtship pheromones by SDS-PAGE gels. The courtship pheromone extracts from a terrestrial salamander R jordani) contain approximately 20 stained protein bands. Protein concentrations were standardized on gels, so band thickness and intensity reflect actual differences. Courtship gland extracts prepared in different years showed a high level of consistency among years, indicating their non-volatility and stability in response to temperature fluctuations (repetitive freezing and thawing). Top arrow indicates isoforms of the protein component Pj-22 bottom arrow indicates isoforms of protein component Pj-10. Lane 1 = protein standards, lane 2 = extract from 1994, lane 3 = extract from 1995, lane 4 = pooled extract from 1992—1995.

Table 1. Average amino acid (aa) composition for four of the major isoforms of Pj-22, a major protein component of the male courtship pheromone from the salamander, R jordanf...

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