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 1.00a(v), where the inability to absorb water vapor from the air fails to equilibrate declining water levels (gain not equal to 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.

Objective: We assessed the extent of energy misreporting from the use of a self-administered 7-day diet record (7-DDR) and a widely used food frequency questionnaire (FFQ) compared to total energy expenditure from doubly labeled water (DLW) in a group of postmenopausal women. Design: At baseline, 65 healthy postmenopausal women were instructed to fill out the National Cancer Institute's (NCI) FFQ and a 7-DDR. Average total energy expenditure using the DLW method was also performed at baseline. Results: On average, the women underestimated total energy intake compared to total energy expenditure assessed from DLW by 37% on the 7-DDR and 42% on the FFQ. Conclusions: These findings suggest that the interpretation of findings from the 7-DDR- and FFQ-based energy-disease association studies in postmenopausal women needs further evaluation. Sponsorship: This research was supported (in part) by the Intramural Program of the NIH (National Cancer Institute).

Hydrogen isotope (δ²H) analysis has been routinely used as an ecological tracer for animal movement and migration, yet a biochemical understanding of how animals incorporate this element in the synthesis of tissues is poorly resolved. Here, we apply a new analytical tool, amino acid (AA) δ²H analysis, in a controlled setting to trace the influence of drinking water and dietary macromolecules on the hydrogen in muscle tissue. We varied the δ²H of drinking water and the proportions of dietary protein and carbohydrates with distinct hydrogen and carbon isotope compositions fed to house mice among nine treatments. Our results show that hydrogen in the non-essential (AANESS) and essential (AAESS) AAs of mouse muscle is not readily exchanged with body water, but rather patterns among these compounds can be described through consideration of the major biochemical pathway(s) used by organisms to synthesize or route them from available sources. Dietary carbohydrates contributed more hydrogen than drinking water to the synthesis of AANESS in muscle. While neither drinking water nor dietary carbohydrates directly contributed to muscle AAESS, we did find that a minor but measurable proportion (10–30%) of the AAESS in muscle was synthesized by the gut microbiome using hydrogen and carbon from dietary carbohydrates. δ²H patterns among individual AAs in mice muscle are similar to those we previously reported for bacteria, which provides additional support that this approach may allow for the simultaneous analysis of different AAs that are more influenced by drinking water (AANESS) versus dietary (AAESS) sources of hydrogen.