Short Term Preservation of Hide Using Vacuum: Influence on Properties of Hide and of Processed Leather

The objective of this work was to investigate vacuum influence on hide preservation time and how it affects hide structure. It was established that vacuum prolongs the storage time without hide tissue putrefaction up to 21 days when the storage temperature is 4°C. The microorganisms act for all storage times, but the action is weak and has no observable influence on the quality of hide during the time period mentioned. The hide shrinkage temperature decrease is negligible, which shows that breaking of intermolecular bonds does not occur. Optical microscopy, infrared spectroscopy and differential scanning calorimetry also did not show any structural changes which can influence the quality of leather produced from such hide. The qualitative indexes of wet blue processed under laboratory conditions and of leather produced during industrial trials are presented. Indexes such as chromium compounds exhaustion, content of chromium in leather, content of soluble matter in dichloromethane, strength properties, and shrinkage temperature were determined. Properties of the leather produced from vacuumed hide under industrial conditions conformed to the requirements of shoe upper leather.     

Environmental drivers of demographics, habitat use, and behavior during a post-Pleistocene radiation of Bahamas mosquitofish (Gambusia hubbsi)

A fundamental goal of evolutionary ecology is to understand the environmental drivers of ecological divergence during the early stages of adaptive diversification. Using the model system of the post-Pleistocene radiation of Bahamas mosquitofish (Gambusia hubbsi) inhabiting blue holes, we used a comparative field study to examine variation in density, age structure, tertiary (adult) sex ratio, habitat use, as well as adult feeding and social behaviors in relation to environmental features including predation risk, interspecific competition, productivity (e.g. chlorophyll a, zooplankton density), and abiotic factors (e.g. salinity, surface diameter). The primary environmental factor associated with ecological differentiation in G. hubbsi was the presence of piscivorous fish. Gambusia hubbsi populations coexisting with predatory fish were less dense, comprised of a smaller proportion of juveniles, and were more concentrated in shallow, near-shore regions of blue holes. In addition to predation risk, the presence of a competitor fish species was associated with G. hubbsi habitat use, and productivity covaried with both age structure and habitat use. Feeding and social behaviors differed considerably between sexes, and both sexes showed behavioral differences between predator regimes by exhibiting more foraging behaviors in the absence of predators and more sexual behaviors in their presence. Males additionally exhibited more aggressive behaviors toward females in the absence of predators, but were more aggressive toward other males in the presence of predators. These results largely matched a priori predictions, and several findings are similar to trends in other related systems. Variation in predation risk appears to represent the primary driver of ecological differentiation in this system, but other previously underappreciated factors (interspecific competition, resource availability) are notable contributors as well. This study highlights the utility of simultaneously evaluating multiple environmental factors and multiple population characteristics within a natural system to pinpoint environmental drivers of ecological differentiation.