Respiratory Metabolism of the Terrestrial Isopod Oniscus asellus L.

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Abstract
Approximately 700 individuals of O. asellus of all sizes were subjected to oxygen consumption tests between March 1963 and March 1964. In the relationship live weight to length a change occurs at approximately 20 mg and 7.5 mm, which also coincides with a change in the respiratory rate to live weight relationship. The high oxygen uptake at live weights less than 20 mg is clearly associated with growth. At weights greater than 20 mg the respiratory rate per unit weight is fairly constant; except during May, June, and July when seasonal aberrance, associated with reproductive activities, occurred. A linear relationship exists between the live weight of an individual and the number of embryos and/or young per brood. Weight increase above 100 mg is mainly accounted for by an increase in the number of young per brood. Seasonal differences in respiratory rates occur in both sexes. The highest respiratory rates per unit weight occur between March and August and are more than twice as high as those obtained for the winter months. Two methods of calculating a "best estimate" of oxygen consumption per unit weight per unit time are given. The two estimates are close: 4. 992 and 5. 328 mm3 02/mg/day.