QUICK SEARCH:   [advanced] Author: Keyword(s):
Home     Help     Feedback     Subscriptions     Archive     Search     Table of Contents

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by WRIGHT, J. C. Articles by MACHIN, J. Search for Related Content PubMed Articles by WRIGHT, J. C. Articles by MACHIN, J.

Journal of Experimental Biology 154,13-30 (1990)
Published by Company of Biologists 1990

Water vapour absorption in terrestrial isopods

JONATHAN C. WRIGHT ¹ and JOHN MACHIN ¹

¹ Department of Zoology, University of Toronto, Toronto, Ontario, Canada M5S 1A1

Continuous and intermittent gravimetric measurements have identified active water vapour absorption (WVA) in three species of terrestrial Isopoda. Water activity thresholds for uptake lie in the range 0.92–0.95. Above the threshold, WVA shows non-saturated kinetics; the rectum apparently serves as a supplementary avenue for fluid resorption during rapid uptake. Standardized uptake fluxes, corrected for vapour pressure deficit, can be varied, allowing animals to balance water losses accurately over long periods.

Blocking experiments have localised the ventral pleon as the uptake site. The pleopods display ventilatory cycling during WVA. Cycle frequency increases with humidity, compensating for changes in activity deficit between uptake fluid and air, and allowing uptake rate to be maximised. Freezing-point depression studies reveal hyperosmotic fluid in the ventral pleon. Osmolalities are compatible with prior uptake rates of the specimens studied.

WVA would allow terrestrial isopods to regulate their water balance in external activities below the haemolymph activity (approximately 0.99) and above the uptake threshold. Liquid water – an alternative source for hydration – is rapidly absorbed across the hydrophilic cuticle, posing severe danger of drowning.

Key words: water vapour absorption, Isopoda, Oniscidea, water activity, pleopods

Accepted on July 2, 1990

This article has been cited by other articles:

				J. C. Wright and P. Westh Water vapour absorption in the penicillate millipede Polyxenus lagurus (Diplopoda: Penicillata: Polyxenida): microcalorimetric analysis of uptake kinetics J. Exp. Biol., July 1, 2006; 209(13): 2486 - 2494. [Abstract] [Full Text] [PDF]