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Columbus, OH, United States

Ben-Hamo M.,Ben - Gurion University of the Negev | Munoz-Garcia A.,Ben - Gurion University of the Negev | Williams J.B.,Aronoff Laboratory | Korine C.,Ben - Gurion University of the Negev | Pinshow B.,Ben - Gurion University of the Negev
Journal of Experimental Biology

Bats hibernate to cope with low ambient temperatures (Ta) and low food availability during winter. However, hibernation is frequently interrupted by arousals, when bats increase body temperature (Tb) and metabolic rate (MR) to normothermic levels. Arousals account for more than 85% of a bat's winter energy expenditure. This has been associated with variation in Tb, Ta or both, leading to a single testable prediction, i.e. that torpor bout length (TBL) is negatively correlated with Ta and Tb. Ta and Tb were both found to be correlated with TBL, but correlations alone cannot establish a causal link between arousal and Tb or Ta. Because hydration state has also been implicated in arousals from hibernation, we hypothesized that water loss during hibernation creates the need in bats to arouse to drink. We measured TBL of bats (Pipistrellus kuhlii) at the same Ta but under different conditions of humidity, and found an inverse relationship between TBL and total evaporative water loss, independent of metabolic rate, which directly supports the hypothesis that hydration state is a cue to arousal in bats. © 2013. Published by The Company of Biologists Ltd. Source

Munoz-Garcia A.,Aronoff Laboratory | Munoz-Garcia A.,Ben - Gurion University of the Negev | Williams J.B.,Aronoff Laboratory
Physiological and Biochemical Zoology

Evaporation through the skin contributes to more than half of the total water loss in birds. Therefore, we expect the regulation of cutaneous water loss (CWL) to be crucial for birds, especially those that live in deserts, to maintain a normal state of hydration. Previous studies in adult birds showed that modifications of the lipid composition of the stratum corneum (SC), the outer layer of the epidermis, were associated with changes in rates of CWL. However, few studies have examined the ontogeny of CWL and the lipids of the SC in nestling birds. In this study, we measured CWL and the lipid composition of the SC during development of nestlings from two populations of house sparrows, one from the deserts of Saudi Arabia and the other from mesic Ohio. We found that desert and mesic nestlings followed different developmental trajectories for CWL. Desert nestlings seemed to make a more frugal use of water than did mesic nestlings. To regulate CWL, nestlings appeared to modify the lipid composition of the SC during ontogeny. Our results also suggest a tighter regulation of CWL in desert nestlings, presumably as a result of the stronger selection pressures to which nestlings are exposed in deserts. © 2011 by The University of Chicago. Source

Clement M.E.,Aronoff Laboratory | Munoz-Garcia A.,Aronoff Laboratory | Munoz-Garcia A.,Ben - Gurion University of the Negev | Williams J.B.,Aronoff Laboratory
Journal of Experimental Biology

Lipids of the stratum corneum (SC), the outer layer of the epidermis of birds and mammals, provide a barrier to water vapor diffusion through the skin. The SC of birds consists of flat dead cells, called corneocytes, and two lipid compartments: an intercellular matrix and a monolayer of covalently bound lipids (CBLs) attached to the outer surface of the corneocytes. We previously found two classes of sphingolipids, ceramides and cerebrosides, covalently bound to corneocytes in the SC of house sparrows (Passer domesticus L.); these lipids were associated with cutaneous water loss (CWL). In this study, we collected adult and nestling house sparrows from Ohio and nestlings from Saudi Arabia, acclimated them to either high or low humidity, and measured their rates of CWL. We also measured CWL for natural populations of nestlings from Ohio and Saudi Arabia, beginning when chicks were 2 days old until they fledged. We then evaluated the composition of the CBLs of the SC of sparrows using thin layer chromatography. We found that adult house sparrows had a greater diversity of CBLs in their SC than previously described. During ontogeny, nestling sparrows increased the amount of CBLs and developed their CBLs differently, depending on their habitat. Acclimating nestlings to different humidity regimes did not alter the ontogeny of the CBLs, suggesting that these lipids represent a fundamental component of SC organization that does not respond to short-term environmental change. © 2012. Published by The Company of Biologists Ltd. Source

Beganyi S.R.,University of Georgia | Beganyi S.R.,Aronoff Laboratory | Batzer D.P.,University of Georgia

Fire is an important natural disturbance in the Okefenokee Swamp. From April-June 2007, wildfire burned 75% of the wetland area. With the existence of extensive pre-fire data sets on community structure and total mercury of invertebrates, the fire presented an opportunity to assess impacts of wildfire on invertebrates. Post-fire collection of samples occurred in September, December, and May, 2007-2009. Sample sites included 13 burned and 8 non-burned (reference) sites. Comparisons of data among pre-fire, post-fire reference, and post-fire burned sites revealed that the major difference between pre-fire communities and post-fire communities was a decrease in the number of water mites. We also found a decrease in mercury concentrations in amphipods, odonates, and crayfish post-fire. The differences between pre-fire and post-fire samples may be confounded by drought conditions during the baseline study. NMDS ordinations and ANOSIM tests suggested that habitat was an important factor; communities in burned cypress differed from reference cypress. Unexpectedly, burned sites had lower mercury concentrations in odonates and crayfish, with variation again being greatest in cypress stands. These findings and others suggest mercury levels do not follow a predictable pattern but can vary with pre-fire concentrations, variation in water levels, and burn intensity. We found that wildfire in the Okefenokee had little impact on invertebrates in prairies and scrub-shrub thickets, but can affect indicator organisms (Oecetis, Ischnura, and Sigara) in cypress stands. Our study suggests that vegetation type and burn intensity may have impacts on the invertebrate communities and mercury concentrations of organisms. © 2011 Springer Science+Business Media B.V. Source

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