METABOLIC RATE AND WATER ECONOMY IN THE DESERT AND MEDITERRANEAN POPULATIONS OF THE COMMON SPINY MOUSE (ACOMYS CAHIRINUS) IN ISRAEL

ABSTRACT

Physiological adaptation to the environment has been studied in two populations of the common spiny mouse, Acomys cahirinus., one from the extreme desert (Elat), and one from the Galilee, an area characterized by temperate Mediterranean conditions. The resting metabolic rate at thermoneutrality in the Elat animals was 0.71 ± 0.13 ml O₂ g⁻¹ h⁻¹. A 20% higher oxygen consumption was recorded in the animals from the Galilee. The lower critical points for the desert and the Galilee animals were 30 °C and 28 °C, respectively. When measured in the laboratory (ambient temperature = 28 °C), the water turnover rate in the Elat animals was 7.14±1.7 ml (100g)⁻¹ day⁻¹, and in the animals from the Galilee, 11.22 ± 0.45 ml (100g)⁻¹ day⁻¹. The field water turnover rate, however, was similar in the two populations (11.13±2.62ml (100g)⁻¹ day⁻¹ and 10.85 ± 3.3 ml (100g)⁻¹ day⁻¹ in the Elat and Galilee animals, respectively) The maximal urine concentration obtained in animals maintained on a high protein, high salt diet was 5663 ± 737 mosmol/kg in the animals from Elat and 3895 ± 224 mosmol/kg in the animals from the Galilee. The present study highlights the relationship of intraspecific variations in metabolism, and water economy, to population geographic distribution.