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Phenotypic Flexibility at the Molecular and Organismal Level Allows Desert‐Dwelling Rodents to Cope with Seasonal Water Availability

1Departamento de Ciencias Fisiológicas, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago 6513677, Chile; 2Centro de Estudios Avanzados de Zonas Áridas and Departamento de Biología, Facultad de Ciencias, Universidad de La Serena, Casilla 599, La Serena, Chile; 3Centro de Estudios Avanzados en Ecología y Biodiversidad, Departamento de Ecología, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago 6513677, Chile

We examined the phenotypic flexibility of field urine osmolality (Uosm) in response to seasonal rainfall and the experimental expression of renal aquaporins (AQPs) in the leaf‐eared mouse Phyllotis darwini, a South American desert‐dwelling rodent, through an integrative study at both the cellular and the organismal level. Field Uosm was higher in summer than in winter. Fall and winter Uosm were not significantly different. During a rainy year, winter Uosm was 2,140 ± 82.3 mOsm kg−1; the corresponding value in a dry year was 2,569 ± 61.3 mOsm kg−1. During the summer, the mean Uosm in a rainy year was 3,321 ± 71.5 mOsm kg−1, and in a dry year it was 3,604 ± 107.2 mOsm kg−1. The distribution of AQP‐2, AQP‐3, and AQP‐4 was similar to that described for mouse and rat kidneys and confined to principal cells in cortex and inner medullary collecting‐duct cells. AQP‐4 immunoreactivity was unaltered by the state of water balance. Relative to water loading, dehydration induced an increase in AQP‐2 immunoreactivity and protein abundance. Although more discrete, AQP‐3 immunolabeling was also increased by dehydration. We now reveal how the integration of flexible renal mechanisms acting at the cellular and organismal level allow a small desert‐dwelling mammal to cope with seasonal and yearly (El Niño) water availability in its semiarid habitat.