Comparative respiratory strategies of subterranean and fossorial octodontid rodents to cope with hypoxic and hypercapnic atmospheres |
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Authors: | I H Tomasco R Del Río R Iturriaga F Bozinovic |
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Institution: | 1. Laboratorio de Evolución, Facultad de Ciencias, Universidad de la República, Iguá 4225, 11400, Montevideo, Uruguay 2. Laboratorio de Neurobiología, Facultad de Ciencias Biológicas, P. Universidad Católica de Chile, Santiago, Chile 3. Departamento de Ecología, Centro de Estudios Avanzados en Ecología y Biodiversidad, Facultad de Ciencias Biológicas, P. Universidad Católica de Chile, Santiago, Chile
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Abstract: | Subterranean rodents construct large and complex burrows and spend most of their lives underground, while fossorial species
construct simpler burrows and are more active above ground. An important constraint faced by subterranean mammals is the chronic
hypoxia and hypercapnia of the burrow atmosphere. The traits, regarded as “adaptations of rodents to hypoxia and hypercapnia”,
have been evaluated in only a few subterranean species. In addition, well-studied subterranean taxa are very divergent to
their sister groups, making it difficult to assess the adaptive path leading to subterranean life. The closely related sister
genera Octodon and Spalacopus of Neotropical rodents offer a unique opportunity to trace the evolution of physiological mechanisms. We studied the ventilatory
responses of selected octodontid rodents to selective pressures imposed by the subterranean niche under the working hypothesis
that life underground, in hypoxic and hypercapnic conditions, promotes convergent physiological changes. To perform this study
we used the following species: Spalacopus cyanus (the subterranean coruros) and Octodon degus (the fossorial degus) from central Chile. Ventilatory tidal volume and respiratory frequency were measured in non-anaesthetized
spontaneously breathing animals. Acute hypoxic challenges (O2 1–15%) and hypercapnia (CO2 10%) were induced to study respiratory strategies using non-invasive whole body pletismography techniques. Our results show
that coruros have a larger ventilatory response to acute hypoxia as than degus. On the other hand, hypercapnic respiratory
responses in coruros seem to be attenuated when compared to those in degus. Our results suggest that coruros and degus have
different respiratory strategies to survive in the hypoxic and hypercapnic atmospheres present in their burrows. |
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