The vomeronasal organ of the South American armadillo Chaetophractus villosus (Xenarthra, Mammalia): anatomy, histology and ultrastructure

The vomeronasal organ (VNO) is a chemoreceptive structure that has not been extensively studied in the Xenarthran order. Tissue samples from the VNO of the armadillo Chaetophractus villosus were prepared for light and electron microscopy. The VNO is located in the anterior part of the base of the nasal septum. It is tubular in shape, ∼ 18 mm in length and opens in the rostral region of the nasal cavity and with a blind caudal end. Its lumen is lined by sensory (SE) and nonsensory (NSE) epithelium. The SE shows sensory, supporting and basal cells whereas the NSE contains ciliated and nonciliated secretory cells and basal cells. At the ultrastructural level, the sensory cells appear as bipolar neurons with conspicuous microvilli on their free surface. The supporting cells of the SE contain numerous membrane-bound vesicles in their apical regions. A peculiar feature not found in other mammals, is the presence of concentric whorls of RER cisterns frequently observed in their basal expansions. Infiltrating plasma cells can be detected in the SE basal region close to the dorsal junctional area. This region also exhibits an unusual type of basal cell, probably responsible for the generation of new vomeronasal receptor neurons. The ciliated NSE cells exhibit numerous ovoids or irregularly shaped membranous protrusions projecting from the plasma membrane of the cilia. As far as we know, this is the first study reporting the presence of this feature in ciliated NSE cells. The nonciliated cells are characterised by scarce large secretory granules and apical microvilli. The vomeronasal glands are compound-branched tubuloacinar glands with serous acinar cells. Four types of secretory granules are present. The ducts of these glands reach the lumen in the dorsolateral region between the NSE and SE. Hypolemmal nerve terminals were observed contacting secretory cells. Fenestrated and nonfenestrated capillaries constitute the vascular supply to these glands. Plasma cells, intimately associated with acinar cells, were frequently observed

Ultrastructural characterisation of the olfactory mucosa of the armadillo Dasypus hybridus (Dasypodidae, Xenarthra)

The ultrastructure of the olfactory mucosa of the armadillo Dasypus hybridus was studied. A comparison with the olfactory mucosa of another armadillo (Chaetophractus villosus) was made. The olfactory mucosa of D. hybridus shows many features which are similar to those of other mammals. Interestingly, it differs from the olfactory mucosa of the armadillo C. villosus. A suggestion is made that these differences may be due to differences in the digging habits of these species. In Dasypus, the supporting cells (SCs) showed dense vacuoles, multivesicular bodies and lysosome-like bodies probably related with the endocytotic system. The SCs show a dense network of SER presumably associated with xenobiotic mechanisms. The olfactory receptor neurons exhibit lysosome-like bodies and multivesicular bodies in their perikarya. These organelles suggest the presence of an endocytotic system. Duct cells of Bowman's glands exhibit secretory activities. Bowman's glands are compound-branched tubulo-acinar mixed glands with merocrine secretory mechanisms

Different factors that modify anti-predator behaviour in guanacos (Lama guanicoe)

Animals optimize the trade-off between the cost of not fleeing and the benefits of staying because the factors that influence flight decisions and the disturbance level of a particular stimulus can vary both spatially and temporally. Different factors (human impact and habitat characteristics) likely to modify anti-predator behaviour in different types of guanaco social groups were analysed. We found that group size was conditioned by high poaching, vehicle traffic, predation risk and vegetation density. Solitary adult males showed shorter alert and flight initiation distances than bachelor and mixed groups. Alert distance was greater during the summer season, and assessment times were shorter when young were present in the groups. In high-predation-risk environments, guanacos detected threats at greater distances and flight initiation distance was longer. Alert distances were shorter on steeper sloped hills and assessment times were shorter in areas with irregular topography than on flat sites. In high traffic areas, flight initiation distance was longer and assessment times were shorter. And in areas with low poaching intensity, assessment times were greater than in those with high poaching levels. Therefore, guanacos may be able to evaluate a true threat. Social group and anti-predator responses were conditioned by habitat characteristics and human impact. We consider that plasticity of responses could be key to the survival of guanacos.Fil: Taraborelli, Paula Andrea. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mendoza. Instituto Argentino de Investigaciones de Zonas Aridas; Argentina. Universidad Nacional del Comahue. Asentamiento Universidad San Martin de Los Andes; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Patagonia Norte. Instituto de Investigación en Biodiversidad y Medioambiente; ArgentinaFil: Ovejero, R.. Universidad Nacional del Comahue. Asentamiento Universidad San Martin de Los Andes; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Patagonia Norte. Instituto de Investigación en Biodiversidad y Medioambiente; ArgentinaFil: Mosca Torres, Maria Eugenia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mendoza. Instituto Argentino de Investigaciones de Zonas Aridas; ArgentinaFil: Schroeder, Natalia. Universidad Nacional del Comahue. Asentamiento Universidad San Martin de Los Andes; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Patagonia Norte. Instituto de Investigación en Biodiversidad y Medioambiente; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mendoza. Instituto Argentino de Investigaciones de Zonas Aridas; ArgentinaFil: Moreno, Pablo Gastón. Universidad Nacional del Comahue. Asentamiento Universidad San Martin de Los Andes; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Patagonia Norte. Instituto de Investigación en Biodiversidad y Medioambiente; Argentina. Universidad Nacional del Litoral. Facultad de Ciencias Veterinarias; ArgentinaFil: Gregorio, Pablo Francisco. Universidad Nacional del Comahue. Asentamiento Universidad San Martin de Los Andes; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Patagonia Norte. Instituto de Investigación en Biodiversidad y Medioambiente; ArgentinaFil: Marcotti, Eugenia. Consejo Nacional de Investigaciones Científicas y Técnicas. Científico Tecnológico Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; ArgentinaFil: Marozzi, Antonela Alejandra. Universidad Nacional del Comahue. Asentamiento Universidad San Martin de Los Andes; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Patagonia Norte. Instituto de Investigación en Biodiversidad y Medioambiente; ArgentinaFil: Carmanchahi, Pablo Daniel. Universidad Nacional del Comahue. Asentamiento Universidad San Martin de Los Andes; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Patagonia Norte. Instituto de Investigación en Biodiversidad y Medioambiente; Argentin