Abstract
Terrestrial isopods (Crustacea, Isopoda, Oniscidea) are capable of active water vapor absorption from subhemolymph water activities. The minimum activity for absorption constitutes the uptake threshold (T), and animals can balance passive losses above the critical equilibrium activity (CEA). Values for Porcellio scaber are 0.889 and 0.913, respectively. Two major mechanisms can explain the uptake process. Maximum attainable uptake fluxes increase linearly with ambient water activity (Aaw) although animals are capable of depressing uptake fluxes below, this curve. Such kinetics are compatible with a steady-state secretion/resorption of hyperosmotic fluid in the pleoventral cavity (PV) and ventilation of ambient air by the pleopodal exopods. At near-threshold activities animals may also reveal sharply augmented uptake fluxes. Comparisons with available data 0on fluid concentrations, and direct observations of pleopodal ventilation, indicate the elevation of Aaw within the PV by pressure cycling. This is confirmed by monitoring pressure fluctuations, coincident with pleopodal ventilations, in an enclosed chamber. Blocking experiments support endogenous secretion/resorption of pleon fluid. Fecal activities are approximately 0.990, discounting a rectal resorption mechanism based on transepithelial activity gradients.
Published Version
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
