Plethodontids

Fig. 3.2 Amphibian protein-chemosignalling PRF (plethodontid receptivity factor interleukin-6), broadcast from male salamander mental gland in the forward current produced by tail-fanning (after Arnold, 1997 Rollman, 1999).

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. 

The chemoreceptive mechanisms in amphibia are undoubtedly worthy of further analysis, not only for their own sake, but to provide clues as to the origination of advanced chemosignal systems. As noted above, a pheromonal signal from the mental gland acts as a courtship/ receptivity inducer. The plethodontid receptivity factor (PRF) (Chap. 3) despite its size (22 kD), seems to have been converted from its internal role as an inter-cellular cytokine, to an inter-individual coordinator of reproductive activity (Rollmann et al., 1999). Endocrine or... 

Brown C. (1968). Additional observations on the function of the naso-labial grooves of Plethodontid salamanders. Copeia, 728-731. 

Feldhoff R.C., Rollman S.M. and Houck L.D. (1999). Chemical analysis of courtship pheromones in a Plethodontid Salamander. In Advances in Chemical Signals in Vertebrates (Johnston R.E., Miiller-Schwarze D. and Sorenson P., eds.). Kluwer, New York, pp. 117-126. 

The function of the male courtship pheromone in plethodontids was first documented in a study of Desmognathus ocoee Houck and Reagan (1990) showed that the diffusion delivery of a crude extract from the male pheromone gland increased... 

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). 

Chippindale, P.R., Bonett, R.M., Baldwin, A.S. and Wiens, J.J. (2004) Phylogenetic evidence for a major reversal of life-history evolution in plethodontid salamanders. Evol. 58, 2809-2822. 

Highton, R. and Peabody, R.B. (2000) Geographic protein variation and speciation in salamanders of the Plethodon jordani and Plethodon glutinosus complexes in the southern Appalachian Mountains with the descriptions of four new species. In R.C. Bruce, R.G. laeger, and L.D. Houck. (Eds.) The biology of plethodontid salamanders. Plenum, New York, pp. 31-94. 

Houck, L.D. and Reagan, N.L. (1990) male courtship pheromones increase female receptivity in a plethodontid salamander. Anim. Behav. 39, 729-734. 

Macey, J.R. (2005) Plethodontid salamander mitochondrial genomics a parsimony evaluation of character conflict and implications for historical biogeography. Qadistics 21, 194—202. 

Amphibia Plethodontids (lungless Chemical Nose tapping Dawley 1987,1992... 

Courtship pheromones are not necessarily species specific. Pairs of the woodland salamander, Plethodon shermani, courted for an equally long time (about 35 to 50 minutes) whether male pheromone from the mental gland of conspecifics or the allopatric species P. montanus or P. yonahlosscc was present, even though the composition of the proteinacous pheromones (plethodontid receptivity factor of these three species differ considerably (Rollmann et al, 2003). 

Male courtship pheromones can increase the receptivity of the female. In the plethodontid salamander Desmognathus ochrophaeus the male courts the female hy scraping her dorsum with his specialized premaxillary teeth and swahs the same area with secretion from the mental gland on his chin, amounting to an injection. In an experiment, filter paper with an extract from the excised mental glands of males was placed on the dorsum of females. These treated females mated 28% (59 minutes) sooner than controls (Houck and Reagan, 1990). 

Salamander vomeronasal systems why plethodontids smell well. American Zoologist 27,166A. 

Placyk, J. S. and Graves, B. M. (2002). Prey detection by vomeronasal chemoreception in a plethodontid salamander. JoarnflZo/C/iem/cflZEcoZo 28,1017-1036. 

Brown, C. W., 1968, Additional observations on the liinetion of the nasolabial grooves of plethodontid salamanders, Copeia 1968 728-731. 

Verrell, P. A., 1989, An experimental study of the behavioral basis of sexual isolation between two sympatric plethodontid salamanders, Desmognathus imitator and D. ochrophaeus. Ethology 80 274-282. 

Wirsig-Wiechmann, C. R., Houck, L. D., Feldhoff, P. W., and FeldhofL R. C., 2002, Pheromonal activation of vomeronasal neurons in plethodontid salamanders. Brain Res. 952 335-344. 

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