Salamander system

In this terrestrial salamander system, chemical signals are broadcast in the environment by reproductively active females and are detected by the males as they tap... 

Storfer, A., 1999, Gene flow and local adaptation in a simflsh-salamander system, Behav. Ecol. Soc. 46 73-79. 

Eisthen H.L. (2000a). Presence of the vomeronasal system in aquatic salamanders. Philos Trans Roy Soc Lond B 355, 1209-1213. 

Froese, J.M., Effects of Dietary Deltamethrin Exposure on the Immune System of Adult Tiger Salamanders Ambystoma tigrinum, M. Sc. Thesis, University of Saskatechewan, Saskatoon, SK, Canada, 2002. 

The demonstration of this behavioural response to a male pheromone signal is significant because of the manner in which the pheromone was delivered. Most other vertebrate examples of reproductive pheromones involve reception via the olfactory system(s). In contrast, D. ocoee females received the pheromone via diffusion through the dorsal skin. We assume that the well developed superficial capillary system of these lungless salamanders is the route by which the male pheromone was transported to whatever target tissue(s) initiated responses that affected female reproductive behaviour. 

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). 

Significant concentrations of cyanotoxins have been found to accumulate in the tissues of macroinvertebrates such as mollusks and crustaceans, presenting an indirect route of exposure for invertebrates, fish, and aquatic mammals at higher trophic levels (Negri and Jones 1995). In natural systems, mortality among benthic invertebrate herbivores is probably low because most bloom-forming bacteria are planktonic and only periodically come into contact with the benthos. Nevertheless, Kotak et al. (1996) determined that enhanced mortality of snails at the end of a bloom cycle in Canadian lakes was due to consumption of Microcystis cells that had formed a scum on the surface of macrophytes. Oberemm et al. (1999) found that aqueous microcystins, saxitoxins, and anatoxin-a all resulted in developmental delays in fish and salamander embryos. Interestingly, more severe malformations and enhanced mortality were observed when larvae were exposed to crude cyanobacterial extracts than to pure toxins applied at natural concentrations (Oberemm et al. 1999). 

The first olfactoiy neuron-specific protein, termed olfactory marker protein was isolated by Frank Margolis in 1972 and was cloned in the 1980s. This 19 kDa cytoplasmatic protein is unique to the mature olfactory system and is found in vertebrates from salamanders to humans (reviewed by Margolis et ah, 1993). 

The terrestrial salamander Plethodonjordani applies courtship pheromone to the female hy ruhhing or slapping his mental gland directly on the female s nares. This way the pheromone can stimulate the vomeronasal organ and accessory olfactory system. Experimental application of mental gland extracts to the nares of females accelerated the time until active courtship started (Houck etal., 1998). 

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

Correlation of salamander vomeronasal and main olfactory system anatomy with habitat and sex behavioral interpretations. In Chemical Signals in Vertebrates, vol. 6, ed. R. L. Doty and D. Miiller-Schwarze, pp. 403-409. New York Plenum. 

Monitoring the electrical activity of the nervous system does not appear to give results that accord with the behavior of conditioned animals. On the one hand, electrical responses are observed for volatile chemical stimuli that tiger salamanders apparently do not smell. On the other hand, no selective attenuation of their electrical responses takes place under conditions that reproducibly impair their behavioral responding to one odor but not to another. 

Orbach, H.S., Cohen, L.B. Optical monitoring of activity from many areas of the in vitro and in vivo salamander olfactory bulb a new method for studying functional organization in the vertebrate central nervous system. J. Neurosci. 3, 2251-2262 (1983)... 

Sexual isolation has arisen among numerous species of geographically isolated populations of salamanders (review by Arnold et al., 1993). Behavioral experiments indicate that the degree of reproductive isolation is stronger between sympatric species of large Plethodon than it is between allopatric populations of these species (Reagan, 1992). Sexual isolation may be due to species-specific differences in the chemosensory systems... 

Dawley, E. M., 1992, Sexual dimorphism in a chemosensory system the role of the vomeronasal organ in salamander reproductive behavior, Copeia 1992(1) 13-120. 

Figure 2. Schematic diagram of the nasal cavities and forebrain of a salamander, illustrating the central projections of the olfactory and vomeronasal systems in dorsal view. Anterior is toward the top of the figure, and only ipsilateral projections are shown. The medial (A) and lateral (B) olfactory tracts arise from the olfactory bulb. (C) The extra-bulbar ol ctory pathway bypasses the olfactory bulb and projects directly to the anterior preoptic area. (D) The accessory olfactory bulb, which receives input from the vomeronasal organ, projects to the lateral amygdala (la). Other abbreviations apoa = anterior preoptic area dp = dorsal pallium Ip = lateral pallium mp = medial pallium ma = medial amygdala s = septum sir = striatum. Based on descriptions in Hetrick, 1927,1933,1948 Kokoros and Northcutt, 1977 and Schmidt and Roth, 1990.

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