The influence of habitat on olfactory organ structure in selected species of salamanders (Salamandridae, Caudata)

Abstract

Morphological observations (LM, TEM, SEM) of olfactory organs were conducted on three representatives of the family Salamandridae which differ in post-metamorphic habitat: the terrestrial fire salamander Salamandra salamandra, the semiaquatic alpine newt Ichthyosaura alpestris and the semiaquatic Himalayan newt Tylototriton verrucosus which exhibit increasing specialization towards life in water. We demonstrated variability in proportional size and shape of the main olfactory chamber (MOC), as well as in the degree of development of the vomeronasal organ (VNO) among the three species. In the fire salamander, the olfactory sensory epithelium was distributed throughout the MOC, while in the alpine and Himalayan newt the olfactory sensory epithelium was organized in strips. The presence of two types of olfactory receptor neurons (ciliated receptor neurons, microvillar receptor neurons) was confirmed in olfactory organs of all examined species. For the first time in amphibians, a subtype of ciliated receptor neuron – the giant neuron (rod-shape neuron), was detected in the MOC of all three salamandrids. The olfactory epithelium also consists of ciliated supporting cells and secretory supporting cells. The presence of goblet cells, mucociliary epithelial cells and squamous epithelial cells was demonstrated in the olfactory organs of all examined species. Our results indicate that the olfactory organs of salamandrids may differ in size, shape and distribution of olfactory epithelium depending on habitat type during the post-metamorphic stages of ontogeny.