Effect of temperature on the splenic mechanism of respiratory compensation in the newt

Abstract

AbstractThe spleen of the newt Triturus cristatus carnifex (Laurenti), an urodele amphibian, hoards erythrocytes when the animal is well‐oxygenated and releases them into the bloodstream when the animal is in a hypoxic condition. Between the extremes of congestion and decongestion the weight of the spleen varies up to a ratio of 6:1. However, the degree of the phenomenon depends on the temperature, which, in ectotherms, regulates metabolic rate and thus oxygen demand. In order to assay the degree of hypertrophy reached by congested spleens in standard respiratory conditions, groups of eight animals—previously anesthetized by immersion for 20 minutes in a 0.2% solution of chlorbutol in tap water at 18°C—were exposed to 100% humid air in a thermostatic chamber set at a temperature of 6, 12, 18, 24, 27, 30, or 33°C. Each animal remained at the set temperature until surpassing the minimum time necessary for maximum hypertrophy to be reached, equal to the time necessary for 4,000 heartbeats. At 33°C the spleens are almost completely bloodless, while at the other temperatures their hypertrophy from congestion increases linearly as the temperature diminishes, reaching maximum values at 6°C. Though the progressive congestion of the spleen as the temperature descends is due mainly to blood cells and only very slightly to plasma, erythrocyte concentration in the blood remains constant at all the lower temperatures up to that of anesthesia (18°C); this phenomenon implies variability of blood volume in the newt. Instead, above 18°C, the values of the hematic parameters increase as the temperature rises, reaching a maximum increment of about 30% by 27°C.