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On November 5-8, 2019, the "Mars Extant Life: What's Next?" conference was convened in Carlsbad, New Mexico. The conference gathered a community of actively publishing experts in disciplines related to habitability and astrobiology. Primary conclusions are as follows: A significant subset of conference attendees concluded that there is a realistic possibility that Mars hosts indigenous microbial life. A powerful theme that permeated the conference is that the key to the search for martian extant life lies in identifying and exploring refugia ("oases"), where conditions are either permanently or episodically significantly more hospitable than average. Based on our existing knowledge of Mars, conference participants highlighted four potential martian refugium (not listed in priority order): Caves, Deep Subsurface, Ices, and Salts. The conference group did not attempt to reach a consensus prioritization of these candidate environments, but instead felt that a defensible prioritization would require a future competitive process. Within the context of these candidate environments, we identified a variety of geological search strategies that could narrow the search space. Additionally, we summarized a number of measurement techniques that could be used to detect evidence of extant life (if present). Again, it was not within the scope of the conference to prioritize these measurement techniques-that is best left for the competitive process. We specifically note that the number and sensitivity of detection methods that could be implemented if samples were returned to Earth greatly exceed the methodologies that could be used at Mars. Finally, important lessons to guide extant life search processes can be derived both from experiments carried out in terrestrial laboratories and analog field sites and from theoretical modeling.

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In Europe polecat populations are declining for unknown reasons during the last decades. Data on the river otter, another mustelid predator, indicate that PCB levels are high enough in some populations to interfere with the reproduction of this aquatic species. Since the diet of the polecats consists to a large amount of aquatic prey (amphibians) it appears reasonable to assume that PCBs ingested with the prey are a factor in the decline of polecats. To test this assumption PCB residues in amphibians and in adipose tissue and liver of polecats from Southwest Germany were quantified and the results were compared with literature data on the reproductive toxicity of PCBs in feral mink. According to the current data total PCB levels in polecats (adipose tissue, mean 1244 ng/g lipids; liver, mean 1677 ng/g lipids) and their prey (frogs, mean 9279 ng/kg fresh weight; toads, 4948 ng/kg fresh weight) are comparatively low. Using the toxic equivalent approach, it was calculated that polecats could feed exclusively on amphibians without consuming a harmful amount of PCBs. Therefore, PCBs cannot be an agent currently affecting polecat populations in Central Europe. Other environmental factors like habitat destruction or road accidents are more likely to have a negative impact on polecat populations.

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Ferrets, mammalian carnivores, kept in an indoor enclosure were continuously exposed to low concentrations of polychlorinated biphenyls (PCBs) in the ambient air for 5 years. After that time PCB concentrations were quantified in the olfactory bulbs and in the remaining brain, adipose tissue and liver. The results revealed unexpectedly high PCB concentrations in the olfactory bulbs, surpassing those in the remaining brain and the peripheral tissues. The PCB congener pattern in the olfactory bulbs resembled that found in the ambient air and the less chlorinated volatile PCBs were found in higher concentrations. We, therefore, assume that airborne PCBs enter directly via the olfactory system and are transported through the axons to the olfactory bulbs where they accumulate.

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The concentrations of non-ortho, mono-ortho and di-ortho substituted PCB congeners in tissues of three European mustelid species--polecat, stone marten and badger--were determined. Median congener concentrations are comparable in the three species and are lower than in previous studies on polecats. In all samples PCB-126 contributes most to the TCDD-TEQ; it occurs in considerably higher concentrations in polecats. Additionally, amphibs, the main prey of polecats, were analysed. The total PCB intake of polecats feeding solely on amphibs would be below a critical level, considering the NOAEL for the reproduction of mink, a closely related species.

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Free-ranging beaver (Castor canadensis) in two different beaver populations in New York State were exposed to predator chemicals to test feeding inhibition. Solvent extracts of feces were applied to stem sections of aspen, the preferred food tree of beavers, permitting smelling and tasting the samples. Predator odors were from wolf (Canis lupus), coyote (Canis latrans), dog (Canis familiaris), black bear (Ursus americanus), river otter (Lutra canadensis), lynx (Lynx canadensis), and African lion (Panthera leo). The experiment was repeated. The predator odors reduced feeding compared to untreated or solvent-treated controls. One population consumed 17.0% of the samples with predator odor and 27.0% of the controls in summer, and 48.4% and 60.0%, respectively, in autumn. The other population accepted 3.15% of the predator odor samples and 11.05% of the controls in summer. Coyote, lynx, and river otter odors had the strongest effects. Diesel oil and bitter-tasting neem extract had weaker effects. Predator odors are promising as feeding repellents for beaver.

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