Modelling and simulation of CO
transport. (A) Reference topology based on a cylinder-within-tubes arrangement (R. Moenickes, O. Richter and R. Pirow, in preparation). A sector piece was removed to show the alternation of concentric hollow cylinders of tissue (gray) and hemolymph (red, green, blue). (B) Simplified topology with only one tissue layer. This topology is applied in the compartment model. (C) Compartment model of the relevant transport processes. CO2 is excreted from the tissue compartment of length dL into the inner and outer hemolymph (HL) lacuna at rates of (1-φ)FEx and φFEx. Hemolymph leaving the inner HL lacuna at a volume-flow rate is distributed between the outer HL lacuna and the carapace HL lacuna. From these compartments CO2 diffuses across cuticular barriers into the medium, which flows at a rate of . Indicated are the CO2 partial pressures (Phi, Pho, Phc, Pm) and flow velocities (νb, νf, νm) in the hemolymph lacunae and the medium. Pin is the inspiratory PCO2. (D) Simulation results for the uncatalyzed and catalyzed hydration of CO2 for an animal exposed to normal conditions (ambient pH = 8.0, ambient PCO2 = 0.035 kPa). Acid-base variables are shown for the medium and hemolymph lacunae in relation to the exchange coordinate.