Respiratory Gas Exchange in Spiders

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Abstract
The functional characteristics of the respiratory gas exchange systems of spiders were evaluated from relationships describing respiratory surface areas, lung volumes, rates of oxygen consumption, and heart rates as functions of change in body size. Most spiders have rates of metabolism lower than those of other poikilotherms: Those spiders with the lowest rates are adapted to live in environments characterized by low energy availability. Rates of metabolism are directly proportional to respiratory surface area and are positively correlated with lung volume. Modification of respiratory or circulatory variables potentially provides for aerobic scopes of three- to eightfold. These estimates agree with those reported for spiders based on measurements of rates of metabolism. These aerobic scopes for spiders are lower than those reported for insects. This comparison underscores the adaptive characteristics associated with the "sit and wait" style of predation in spiders. Their use of silk snares and poison to capture prey as well as their well-developed anaerobic capacity and ability to disperse passively by ballooning alleviates the necessity for high aerobic capabilities.