RESUMEN
Given the rapid loss of biodiversity as consequence of climate change, greater knowledge of ecophysiological and natural history traits are crucial to determine which environmental factors induce stress and drive the decline of threatened species. Liolaemus montanezi (Liolaemidae), a xeric-adapted lizard occurring only in a small geographic range in west-central Argentina, constitutes an excellent model for studies on the threats of climate change on such microendemic species. We describe field data on activity patterns, use of microhabitat, behavioral thermoregulation, and physiology to produce species distribution models (SDMs) based on climate and ecophysiological data. Liolaemus montanezi inhabits a thermally harsh environment which remarkably impacts their activity and thermoregulation. The species shows a daily bimodal pattern of activity and mostly occupies shaded microenvironments. Although the individuals thermoregulate at body temperatures below their thermal preference they avoid high-temperature microenvironments probably to avoid overheating. The population currently persists because of the important role of the habitat physiognomy and not because of niche tracking, seemingly prevented by major rivers that form boundaries of their geographic range. We found evidence of habitat opportunities in the current range and adjacent areas that will likely remain suitable to the year 2070, reinforcing the relevance of the river floodplain for the species' avoidance of extinction.
Asunto(s)
Adaptación Fisiológica , Regulación de la Temperatura Corporal/fisiología , Especies en Peligro de Extinción , Lagartos/fisiología , Animales , Argentina , Temperatura Corporal , Cambio Climático , Conservación de los Recursos Naturales/métodos , Ecosistema , Femenino , Calor , MasculinoRESUMEN
Silvinichthys huachi new species, is described from a stream along the lower slope of the Andean Cordillera in the Provincia de San Juan, Argentina. It shares the distinctive modifications characteristic of Silvinichthys, but is distinguished from the four previously described congeners by the combination of a lack of the pelvic fin and the pelvic girdle, details of pigmentation and various meristic and morphometric features. Silvinichthys huachi is apparently endemic to the type locality situated within an arid region of western central Argentina in the Andino Cuyana Province. Major gaps in the range of species of Silvinichthys may indicate that the origin of the genus predates the uplift events that subdivided drainages along the eastern slopes of the Andean Cordillera in west central Argentina. Silvinichthys huachi is hypothesized to be the sister species of Silvinichthys bortayro.
Asunto(s)
Bagres/anatomía & histología , Aletas de Animales , Animales , Argentina , PigmentaciónRESUMEN
Although very rare, cases of cauda equina tumours migrating several levels have been known to occur. We report two cases of cauda equina schwannomas which migrated from its primary site, one caudally and the other one rostrally as confirmed by magnetic resonance imaging perioperatively. The first patient was a 27-year-old man and the second a 41-year-old man; both presented with back pain. This report aims to remind clinicians that certain tumours attached to the roots in the lumbar spinal canal may migrate.