In Saccharomyces cerevisiae, the diffusion rate of hydrogen peroxide (H2O2) through the plasma membrane decreases during adaptation to H2O2 by means of a mechanism that is still unknown. Here, evidence is presented that during adaptation to H2O2 the anisotropy of the plasma membrane increases. Adaptation to H2O2 was studied at several times (15min up to 90min) by applying the steady-state H2O2 delivery model. For wild-type cells, the steady-state fluorescence anisotropy increased after 30min, or 60min, when using 2-(9-anthroyloxy) stearic acid (2-AS), or diphenylhexatriene (DPH) membrane probe, respectively. Moreover, a 40% decrease in plasma membrane permeability to H2O2 was observed at 15min with a concomitant two-fold increase in catalase activity. Disruption of the ergosterol pathway, by knocking out either ERG3 or ERG6, prevents the changes in anisotropy during H2O2 adaptation. H2O2 diffusion through the plasma membrane in S. cerevisiae cells is not mediated by aquaporins since the H2O2 permeability constant is not altered in the presence of the aquaporin inhibitor mercuric chloride. Altogether, these results indicate that the regulation of the plasma membrane permeability towards H2O2 is mediated by modulation of the biophysical properties of the plasma membrane.

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Eurasian otter, Lutra lutra (L., 1758), spraints collected at the Aguieira hydroelectric dam (central Portugal, n = 916) and tributaries (n = 412) were analysed to assess diet compared with prey availability. Fish and crayfish abundances in the reservoir were assessed with fyke and trammel nets. Prey availability in the tributaries was estimated by electrofishing. In both the reservoir and its tributaries, fish were the main prey and consisted predominantly of Lepomis gibbosus (L., 1758) (60%–65% of occurrences), which is an introduced species of Centrachidae that is abundant in the reservoir but is almost absent in the tributaries. These data suggest that otters using the tributaries feed predominantly in the reservoir. Seasonal dietary variations corresponded to increased availability of nonfish prey categories. Capture vs. consumption analyses demonstrated that otters did not consume L. gibbosus according to its availability. In fact, L. gibbosus was consumed less frequently when other prey species were more available (e.g., amphibians, eels, barbells). The tributaries offer important otter refuge areas that are scarce at the edge of the reservoir, and so, in large reservoirs care should be taken to minimize disturbance in the surrounding catchments. Results indicate that otter populations make use of these conjoint systems to ensure their survival.

The number of dams is progressively increasing, but nonetheless there are few examples of long‐term studies involving otters and these structures. This study assessed how Eurasian otter Lutra lutra responded over time to environmental changes imposed by the construction of a large reservoir, the Alqueva Dam (250 km2, SE Portugal). Otter distribution was monitored over four phases (pre‐deforestation/flooding, deforestation, flooding, and post‐flooding) from 2000 to 2006 in both the flooded and surrounding areas. During each phase, presence was assessed at two resolutions: 25 km2 (76 survey sites in wet and dry seasons) and 1 km2 (39 survey sites, every three months). In addition, otter spraints were collected at eight survey sites in 2000 (pre‐dam) and 2006 (post‐dam) to assess and compare otter diet with prey availability. Otters were widespread before dam construction (>82.4% positive cells), decreased during deforestation (68.5%), and particularly during the flooding phase (33.3%), recovered during the post‐flooding phase, although not at the level recorded before dam construction (61.5–83.3%). Otter diet was dominated by fish and American crayfish Procambarus clarkii during the pre‐deforestation/flooding phase (56.7% fish, 35.3% crayfish) and at the end of the post‐flooding phase (60.7% fish, 33.2% crayfish). Species richness of fish prey decreased with flooding (16 to 8), as did the ratio of native/non‐native fish species (1.7 to 0.3). Changes in the availability of the main ecological requirements of otter were similar to the changes in the observed otter distribution in the flooded area throughout the impact phases, and decreased during deforestation and flooding with some recovery in the post‐flooding phase. The results emphasize the importance of long‐term monitoring studies that include several post‐impact phases, to evaluate species response to impacts. This will allow better planning of mitigation and compensation measures. Copyright © 2013 John Wiley & Sons, Ltd.