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Loxoscelism (bites by spiders of the genus Loxosceles) is the only proven arachnological cause of dermonecrosis. Although Loxosceles spiders can be found worldwide, their distribution is heavily concentrated in the Western Hemisphere, particularly the tropical urban regions of South America. Although Loxosceles bites are usually mild, they may ulcerate or cause more severe, systemic reactions. These injuries mostly are due to sphingomyelinase D in the spider venom. There is no proven effective therapy for Loxosceles bites, although many therapies are reported in the literature.

Malignant melanoma presents a substantial clinical challenge. Current diagnostic methods are limited in their ability to diagnose early disease and accurately predict individual risk of disease progression and outcome. The lack of adequate approaches to properly define disease subgroups precludes rational treatment design and selection. Better tools are urgently needed to provide more accurate

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Summit metabolic rate (M sum , maximum cold-induced metabolic rate) is positively correlated with cold tolerance in birds, suggesting that high M sum is important for residency in cold climates. However, the phylogenetic distribution of high M sum among birds and the impact of its evolution on current distributions are not well understood. Two potential adaptive hypotheses might explain the phylogenetic distribution of high M sum among birds. The cold adaptation hypothesis contends that species wintering in cold climates should have higher M sum than species wintering in warmer climates. The flight adaptation hypothesis suggests that volant birds might be capable of generating high M sum as a byproduct of their muscular capacity for flight; thus, variation in M sum should be associated with capacity for sustained flight, one indicator of which is migration. We collected M sum data from the literature for 44 bird species and conducted both conventional and phylogenetically informed statistical analyses to examine the predictors of M sum variation. Significant phylogenetic signal was present for log body mass, log mass-adjusted M sum , and average temperature in the winter range. In multiple regression models, log body mass, winter temperature, and clade were significant predictors of log M sum . These results are consistent with a role for climate in determining M sum in birds, but also indicate that phylogenetic signal remains even after accounting for associations indicative of adaptation to winter temperature. Migratory strategy was never a significant predictor of log M sum in multiple regressions, a result that is not consistent with the flight adaptation hypothesis. The interplay between physiology and climate can have important consequences for animal distributions. Cold climates require high thermoregulatory energy expenditures for endothermic vertebrates, particularly for small species with high surface area to volume ratios and limited insulatory capacities (Schmidt-Nielsen 1984). Basal (BMR) and maximal cold-induced (=summit metabolism, M sum ) metabolic rates are correlated with climate in mammals, with higher metabolic rates associated with the higher thermoregulatory demands of cold climates (Bozinovic and Rosenmann 1989;Rezende et al. 2004). A similar correlation of BMR with climate also occurs in birds (Weathers 1979), but such correlations of M sum with climate for birds have not been established, primarily because measurements of M sum have mostly been restricted to cold-climate species. The role of winter temperature and the interplay between temperature and metabolism in affecting bird distributions are unclear. Root (1988) found that 1 8 4

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Survival of small birds in fluctuating environments is facilitated by seasonal metabolic and morphological flexibility. Chinese bulbuls Pycnonotus sinensis show winter increases in resting metabolic rate (RMR), nutritional organ masses, and liver and muscle cellular aerobic capacity relative to summer. In this study, we build on these findings from previous studies by measuring seasonal adjustments in body mass (Mb), RMR, nutritional and exercise organ masses, and several physiological, biochemical, and hormonal markers over the entire annual cycle in wild-trapped Chinese bulbuls from Wenzhou, China. Furthermore, we analyzed the relationships between variation in organ masses and cellular aerobic capacity and variation in RMR in individual birds. Mb and RMR were higher in spring (March-May) and winter (December-February) than in summer (June-August). The dry masses of several nutritional organs and mitochondrial protein content, state 4 respiration, and cytochrome c oxidase (COX) activity in liver and muscle were all heightened in winter relative to other seasons. In addition, dry masses of heart and pectoral muscle, but not nutritional organs, and biochemical markers of cellular aerobic capacity in liver and muscle were positively correlated with RMR. Plasma triiodothyronine (T3) concentration was higher in winter and spring than in summer and autumn, and it was positively correlated with RMR, mitochondrial protein content, state 4 respiration, and COX activity in liver and muscle. These results suggest that seasonal changes in nutritional and exercise organ masses and liver and muscle cellular aerobic capacity interact to promote seasonal metabolic flexibility in Chinese bulbuls. T3 appears to promote these seasonal thermoregulatory adjustments.

The roles of ultimate and proximate factors in regulating basal and summit metabolic rates of passerine birds during winter have received little study, and the extent to which winter temperatures affect these variables is unknown. To address this question, we measured basal and summit (maximum cold-induced) metabolic rates in black-capped chickadees (Poecile atricapillus), dark-eyed juncos (Junco hyemalis), and American tree sparrows (Spizella arborea) during winters from 1991/1992 to 1997 in southeastern South Dakota. Both temperature and these metabolic rates varied within and among winters. Least-squares regression revealed significant negative relationships for normalized basal and summit metabolism against mean winter temperature for all species pooled (R2=0.62 to 0.69, P