OXYGEN CONSUMPTION RELATED TO TEMPERATURE AND PHOTOPERIOD IN Oxidus gracilis (Diplopoda, Polydesmida, Strongylosomidae)

Abstract

The respiratory metabolism of Oxidus gracilis was searched considering the parameters temperature and photoperiod trying, in the first case, to detect accidental compensatory adjusts imposed by temperature variations, and in the second, the metabolic changes of the activity rhythm in the 24 hours period. In both cases the data were obtained in a microrespirometer of Warburg, using flasks of 20 ml containing 0,3 ml of 14% KOH solution for absorption of the CO2 exhaled in respiration. The tests with temperature were made at 5°, 10°, 15°, 20°, 25°, 30°, 35° and 40°C, and in those ones of metabolic rhythms, the measures were made only at 25°C, during 24 hours, in which the data were collected during one hour every 3 hours. The data were shown as respiratory rates translated into m l O2 g(live)-1.hour-1. The results showed the occurrence of one metabolic stablishing in the R-T curve (Respiration-Temperature), and "plateaux" were detected among the temperatures of 20° and 25°, 25° and 30°, 30° and 35°, as well as among 20° and 30°, 20° and 35°, and between 15° and 30°C. Below 15°C, that is, at 10° and 5° the millipedes got emotionless by cold in a situation of reversible narcosis. At the high temperatures, between 35° and 40°C, it was detected the smallest index of metabolic range (Q10=0,52), and at 40°C some millipedes showed the effects of torpor by the heat. In the tests of rhythms of 24 hours, the respiratory rates of Oxidus gracilis were higher at night than during the day, confirming data widely found in the literature about the nocturnal behavioral habits of millipedes in general. The results also suggest the existence of a metabolic control mechanism for temperature variations in Oxidus gracilis, and its nocturnal behavior could indicate, besides an expected energetic economy, a good resource to control the water loss by dehydration.