Prolonged maintenance of water balance by adult females of the American spider beetle, Mezium affine Boieldieu, in the absence of food and water resources

• Published in: Journal of insect physiology Vol. 51; no. 5; pp. 565 - 573
• Main Authors: Benoit, Joshua B., Yoder, Jay A., Rellinger, Eric J., Ark, Jacob T., Keeney, George D.
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.05.2005
• Subjects: Animals; Anobiidae; Araneae; body water; Coleoptera - physiology; dehydration (animal physiology); desiccation resistance; Female; Food Deprivation - physiology; Gibbium; Gibbium aequinoctiale; insect behavior; insect cuticle; Mezium; Mezium affine; physiological regulation; Prostephanus truncatus; Ptinidae; Quiescence; Species Specificity; Spider beetle; starvation; Time Factors; Water - metabolism; water activity; Water balance; water content; water deprivation; water gain; water loss; water requirement; water retention; water stress; Water vapor activity; Water vapor activity; Water balance; Mezium affine; Spider beetle; Quiescence
• ISSN: 0022-1910; 1879-1611
• DOI: 10.1016/j.jinsphys.2005.03.001

Moisture requirements were evaluated for female adults of spider beetles Mezium affine Boieldieu and Gibbium aequinoctiale Boieldieu to determine how they are differentially adapted for life in a dry environment. Features showing extreme desiccation resistance of M. affine were an impermeable cuticle wherein activation energies (43 kJ/mol) were suppressed, daily water losses as little as 0.3%/day with an associated group effect, a low 64% water content and an impressive ability to survive nearly 3 months with no food and water. Behaviorally, the extended period of water stress and fasting was marked by long intervals of physical inactivity (quiescence), as though dead. These characteristics emphasizing water retention rather than gain are shared by G. aequinoctiale and reflect a typical xerophilic water balance profile. Water uptake was restricted to imbibing liquid, as evidenced by uptake of dye-stained droplets of free water and a critical equilibrium activity of 1.00 a v, where the inability to absorb water vapor from the air fails to equilibrate declining water levels (gain≠loss) except at saturation. Four-fold reduction in survival time within dry air and accelerated water loss rates with high activation energies for female adults of the closely related winged Prostephanus truncatus (Say) suggest that the enhanced water conservation of spider beetles is due, in part, to fusion of their elytra supplemented by entering into quiescence.