Respiratory refinements in the mygalomorph spider Grammostola rosea Walckenaer 1837 (Araneae, Theraphosidae)

In this study we hypothesized that Grammostola rosea Walckenaer 1837, an active predator of large size that depends on its two paired book lungs for respiration, would have a refined low energy strategy based on its thin air-hemolymph barrier. The morphology of book lungs and the oxygen consumption at 20° and 30°C under normal and starvation conditions were studied. The oxygen consumption was low compared to that expected for spiders from the allometric relationship, 0.027 ± 0.01 ml O2 g-1 h-1 (average ± standard deviation), and it was depressed at 30°C under starvation. The harmonic mean thickness of the air-hemolymph barrier was 0.14 ± 0.03 μm, the respiratory surface density was 122.99 ± 35.84 mm-1, and the book lung volume ranged from 12.2 to 37.5 mm3. With these parameters a high oxygen diffusion capacity was estimated. The combination of low resting oxygen consumption and high pulmonary oxygen conductance results in very low gradients of partial oxygen pressures across the air-h