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Mink
Kinds of Mink Selected AbstractsMolecular impact of MinK on the enantiospecific block of IKs by chromanolsBRITISH JOURNAL OF PHARMACOLOGY, Issue 8 2000C Lerche Slowly activating IKs (KCNQ1/MinK) channels were expressed in Xenopous oocytes and their sensitivity to chromanols was compared to homomeric KCNQ1 channels. To elucidate the contribution of the ,-subunit MinK on chromanol block, a formerly described chromanol HMR 1556 and its enantiomer S5557 were tested for enantio-specificity in blocking IKs and KCNQ1 as shown for the single enantiomers of chromanol 293B. Both enantiomers blocked homomeric KCNQ1 channels to a lesser extent than heteromeric IKs channels. Furthermore, we expressed both WT and mutant MinK subunits to examine the involvement of particular MinK protein regions in channel block by chromanols. Through a broad variety of MinK deletion and point mutants, we could not identify amino acids or regions where sensitivity was abolished or strikingly diminished (>2.5 fold). This could indicate that MinK does not directly take part in chromanol binding but acts allosterically to facilitate drug binding to the principal subunit KCNQ1. British Journal of Pharmacology (2000) 131, 1503,1506; doi:10.1038/sj.bjp.0703734 [source] The Smell of New Competitors: The Response of American Mink, Mustela vison, to the Odours of Otter, Lutra lutra and Polecat, M. putoriusETHOLOGY, Issue 5 2009Lauren A. Harrington We tested the response of wild American mink (an established alien species in the UK), to the odours of unfamiliar mink, European polecat and Eurasian otter. Polecats are similar in size and habits to mink, otters are larger than mink and a dominant competitor; both are native to the UK and both were absent during the original colonization by mink but are now undergoing natural population recoveries. The response of mink to experimental odours was assessed by counting the numbers of tracks (footprints) on rafts treated with anal gland secretions, and compared with response to a control raft, on two rivers in the Upper Thames valley, UK. Remote video showed that the number of tracks was positively correlated with the time that mink spent investigating an odour. We found that mink were attracted to the odours of both unfamiliar mink and polecats. There was little evidence that mink avoided the odour of otters. We suggest that, during an encounter with a polecat, mink may behave much as they would to a conspecific. We infer from the response of mink to the odour of otters, that, if mink do avoid otters, the mechanism of avoidance is likely to be complex, situation-dependent and perhaps affected by prior experience. [source] Modelling the benefits of American Mink Mustela vison management options for terns in west ScotlandIBIS, Issue 2008NORMAN RATCLIFFE American Mink Mustela vison is a semi-aquatic predator that has invaded the west coast of Scotland and many of its associated islands. We developed a GIS model of their potential range based on their dispersal abilities and habitat use, which revealed that most islands in west Scotland are accessible to Mink, and that these host a large proportion of the region's Common Sterna hirundo and Arctic Terns S. paradisaea. Mink are predators on tern eggs and chicks, and statistical modelling of long-term productivity data demonstrated that unprotected sites within their range have an average productivity of 0.33 chicks per pair, whereas that at sites where Mink were trapped was 253% higher. We assessed the benefits of current Mink control projects for terns in the Western Isles and the remainder of west Scotland using a population modelling approach. This showed that both projects delivered considerable benefits for Common Terns, because a large proportion of their numbers were within the area of the control programmes and in sites that would be accessible to Mink if no control were in operation. For Arctic Terns, the benefits were less clear, as a larger proportion of their numbers were outside the control areas, and many of these were in sites isolated from, or unsuitable for, Mink. We discuss the implications of these findings for future strategic planning of Mink management in west Scotland. [source] Chronic effects of polychlorinated dibenzofurans on mink in laboratory and field environmentsINTEGRATED ENVIRONMENTAL ASSESSMENT AND MANAGEMENT, Issue 2 2009Matthew J Zwiernik Abstract Mink are often used as a sentinel species in ecological risk assessments of chemicals such as polychlorinated biphenyls (PCBs), dibenzo- p -dioxins (PCDDs), and dibenzofurans (PCDFs) that cause toxicity mediated through the aromatic hydrocarbon receptor. Considerable toxicological information is available on the effects of PCBs and PCDDs on mink, but limited toxicological information is available for PCDFs. Thus, exposure concentrations at which adverse effects occur could not be determined reliably for complex mixtures in which PCDFs dominate the total calculated concentration of 2,3,7,8-tetrachlorodibenzo- p -dioxin equivalent (TEQ). Two studies were conducted to evaluate the potential toxicity of PCDFs to mink. The first was a chronic exposure, conducted under controlled laboratory conditions, in which mink were exposed to 2,3,7,8-tetrachlorodibenzofuran (2,3,7,8-TCDF) concentrations as great as 2.4 × 103 ng 2,3,7,8-TCDF/kg wet-weight (ww) diet or 2.4 × 102 ng TEQ2006-WHO-mammal/kg ww diet. In that study, transient decreases in body masses of kits relative to the controls was the only statistically significant effect observed. The second study was a 3-y field study during which indicators of individual health, including hematological and morphological parameters, were determined for mink exposed chronically to a mixture of PCDDs and PCDFs under field conditions. In the field study, there were no statistically significant differences in any of the measured parameters between mink exposed to a median estimated dietary dose of 31 ng TEQ2006-WHO-mammal/kg ww and mink from an upstream reference area where they had a median dietary exposure of 0.68 ng TEQ2006-WHO-mammal/kg ww. In both studies, concentrations of TEQ2006-WHO-mammal to which the mink were exposed exceeded those at which adverse effects, based on studies with PCDD and PCB congeners, would have been expected. Yet in both instances where PCDF congeners were the sole or predominant source of the TEQ2006-WHO-mammal, predicted adverse effects were not observed. Taken together, the results of these studies suggest that the values of the mammalian-specific toxicity equivalency factors suggested by the World Health Organization overestimate the toxic potency of PCDFs to mink. Therefore, hazard cannot be accurately predicted by making comparisons to toxicity reference values derived from exposure studies conducted with PCBs or PCDDs in situations where mink are exposed to TEQ mixtures dominated by PCDFs. [source] Impact of released Eurasian otters on a population of American mink: a test using an experimental approachOIKOS, Issue 1 2004L. Bonesi Competition is considered to be a major evolutionary driving force within assemblages of related and morphologically similar species, but it is notoriously difficult to test and quantify especially amongst species that cannot be easily manipulated in a laboratory or in the field. By exploiting a re-introduction of Eurasian otters (Lutra lutra) in the Upper Thames catchment (UK) in 1999 we performed an experiment to test whether there was evidence of competition between otters and American mink (Mustela vison). Mink and otters are semi-aquatic mustelids belonging to the same guild. Otters are expected to be the dominant competitor because they are larger and better adapted at exploiting aquatic resources. Our hypothesis was that mink declines when the density of otters increases. We measured the effect of competition at the population level, by observing whether mink distribution and densities changed in an area of 1353 km2 in association with the arrival of its putative competitor. We estimated distribution and densities by means of sign surveys and trapping. The results showed that otters were associated with a significant and rapid reduction in the densities of mink, while mink occupancy remained approximately the same in an area of 2464 km2 that was used as a control. We observed that the spatial distribution of the mink population throughout its decline was influenced by the yearly cycle of mink activities, with areas being temporarily re-colonized during the dispersal season. Mink is an invasive species in the UK threatening the survival of some native species. Our findings suggest that the re-establishment of otter populations is likely to lead to a decline of mink that may, in turn, be beneficial to native species threatened by this invasive. [source] Competition between Eurasian otter Lutra lutra and American mink Mustela vison probed by niche shiftOIKOS, Issue 1 2004Laura Bonesi Interspecific competition is one of several constraints that might prevent an individual from maximising its energy intake. When an interspecific competitor is introduced, an individual is often forced to shift its diet according to the intensity of the competitive pressure. In this paper, we explore whether the introduced American mink (Mustela vison Schreber) shifts its diet when the density of its potential competitor, the Eurasian otter (Lutra lutra L.), is increased. We compared the diets of otter and mink at the same location but at two moments in time when the relative densities of these two species were different while controlling for the abundance of aquatic prey. Mink and otters are semi-aquatic mammals belonging to the same guild of mustelids and otters are expected to be the dominant competitor because they are larger and better at hunting underwater. The diets of otters and mink overlap to a great extent but while otters specialise mainly on aquatic prey, mink are able to exploit both aquatic and terrestrial prey. These observations prompted the hypothesis investigated in this work that at higher otter densities the diet of mink should change to include a higher proportion of terrestrial items. This hypothesis was supported by the data and at higher otter densities mink diet was observed to consist of a higher proportion of mammals and birds while fewer fish were present, although this pattern was present only in winter while no changes were observed in spring. Meanwhile the diet of otters remained basically unchanged. In the second part of the study, we investigated whether niche breadth and niche overlap between otter and mink changed at different otter densities. We found that niche overlap declined as the density of otters increased, in agreement with the prediction of habitat selection theory. [source] Exposure and effects assessment of resident mink (Mustela vison) exposed to polychlorinated dibenzofurans and other dioxin-like compounds in the Tittabawassee River basin, Midland, Michigan, USA,ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 10 2008Matthew J. Zwiernik Abstract Historically, sediments and floodplain soils of the Tittabawassee River (TR; MI, USA) have been contaminated with polychlorinated dibenzofurans (PCDFs), polychlorinated dibenzo- p -dioxins (PCDDs), and polychlorinatedbiphenyls (PCBs). Median concentrations of 2,3,7,8-tetrachlorodibenzo- p -dioxin equivalents (TEQs) based on 2006 World Health Organization tetrachloro-dibenzo- p -dioxin toxic equivalency factors (TEFs) in the diet of mink (Mustela vison) ranged from 6.8 × 10,1 ng TEQ/kg wet weight upstream of the primary source of PCDF to 3.1 × 101 ng TEQ/kg wet weight downstream. Estimates of toxicity reference values (TRVs) derived from laboratory studies with individual PCDDs/PCDFs and PCB congeners or mixtures of those congeners, as well as application of TEFs, were compared to site-specific measures of mink exposure. Hazard quotients based on exposures expressed as concentrations of TEQs in the 95th percentile of the mink diet or liver and the no-observable-adverse-effect TRVs were determined to be 1.7 and 8.6, respectively. The resident mink survey, however, including number of mink present, morphological measures, sex ratios, population age structure, and gross and histological tissue examination, indicated no observable adverse effects. This resulted for multiple reasons: First, the exposure estimate was conservative, and second, the predominantly PCDF congener mixture present in the TR appeared to be less potent than predicted from TEQs based on dose,response comparisons. Given this, there appears to be great uncertainty in comparing the measured concentrations of TEQs at this site to TRVs derived from different congeners or congener mixtures. Based on the lack of negative outcomes for any measurement endpoints examined, including jaw lesions, a sentinel indicator of possible adverse effects, and direct measures of effects on individual mink and their population, it was concluded that current concentrations of PCDDs/PCDFs were not causing adverse effects on resident mink of the TR. [source] Dietary accumulation, disposition, and metabolism of technical pentabrominated diphenyl ether (DE-71) in pregnant mink (Mustela vison) and their offspring,ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 5 2008Si Zhang Abstract Concentrations of polybrominated diphenyl ethers (PBDEs) in humans and wildlife suggest significant bioaccumulation potential in mammals, but no quantitative biomagnification data from controlled experiments are currently available. As part of a larger study examining the effects of PBDEs on mink (Mustela vison) reproduction and development, we examined congener-specific tissue distribution, maternal transfer, biotransformation, and biomagnification of the technical penta-BDE mixture, DE-71, in farmed mink. Adult female mink were fed one of four concentrations of DE-71 (0-2.5 ,g/g) in the diet from breeding through gestation and until weaning at 6 weeks postparturition. Parent PBDEs were measured in tissues and excreta of adult mink, kits, and juveniles, whereas hydroxylated PBDEs (OH-PBDEs) were measured in juveniles only. Similar lipid-normalized concentrations of PBDEs were detected in most tissues of adult mink with the exception of brain, in which concentrations were significantly lower. Kits, however, had a higher proportion of PBDEs in brain compared with adults, presumably because of incomplete development of the blood-brain barrier. Maternal transfer favored lower-brominated PBDE congeners, and the bulk of the body burden in kits at weaning resulted from lactational rather than transplacental transfer. Lipid-normalized, whole-body biomagnification factors ranged from 0.5 to 5.2 for the major congeners and were highest for BDEs 47 and 153. Metabolism clearly limited the biomagnification of some PBDEs, and OH-PBDEs were detectable in plasma, liver, and feces. On a mass basis, OH-PBDEs accounted for 28 to 32% of the excreted fraction, indicating metabolism was an important elimination pathway. Further studies are required to understand the mechanisms of PBDE biotransformation. [source] Dietary exposure of mink (Mustela vison) to fish from the Housatonic River, Berkshire County, Massachusetts, USA: Effects on reproduction, kit growth, and survivalENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 6 2006Steven J. Bursian Abstract We evaluated the effects of feeding farm-raised mink (Mustela vison) diets containing polychlorinated biphenyl (PCB)-contaminated fish from the Housatonic River (HR; Berkshire County, MA, USA) on adult reproductive performance and kit growth and survival. Diets contained 0.22,3.54% HR fish, providing 0.34,3.7 ,g total PCBs (TPCB)/g feed wet wt (3.5,68.5 pg toxic equivalence [TEQ]/g). Female mink were fed diets before breeding through weaning of kits. Twelve kits from each treatment were maintained on their respective diets for an additional 180 d. Dietary PCBs had no effect on the number of offspring produced, gestation period, or other measures of adult reproductive performance. Mink kits exposed to 3.7 ,g TPCB/g feed (68.5 pg TEQ/g) in utero and during lactation had reduced survivability between three and six weeks of age. The lethal concentrations to 10 and 20% of the population (LC10 and LC20, respectively) were estimated to be 0.231 and 0.984 ,g TPCB/g feed, respectively. Because inclusion of PCB-contaminated fish that composed approximately 1% of the diet would reduce mink kit survival by 20% or more, it is likely that consumption of up to 30-fold that quantity of HR fish, as could be expected for wild mink, would have an adverse effect on wild mink populations. [source] Vitamins A1 and A2 in hepatic tissue and subcellular fractions in mink feeding on fish-based diets and exposed to Aroclor 1242ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 2 2002Anne Käkelä Abstract Two-month-old female mink were fed diets based on either Baltic herring (Clupea harengus membras) or freshwater smelt (Osmerus eperlanus) for 21 weeks. A portion of the smelt-fed mink were exposed orally to polychlorinated biphenyls (PCBs), Aroclor 1242 (1 mg/d). Retinol (vitamin A1), 3,4-didehydroretinol (vitamin A2), and their different fatty acyl esters were studied in hepatic tissue, microsomes, and cytosol by argentated reversed-phase high-performance liquid chromatography. As a result of Aroclor exposure, concentrations of the fatty acyl esters of vitamins A1 and A2 were about one-tenth and those of unesterified A2 one-fourth those of the control levels. In the fatty acyl esters, percentages of stearates (A1 -18:0 and A2 -18:0) increased at the expense of the other fatty acyl esters. The Aroclor exposure decreased concentrations of alcoholic and esterified forms of the A2 analog more than those of the corresponding A1 analog. In microsomes, Aroclor decreased the alcoholic and esterified vitamin analogs to the same extent (to 9,17%). In the cytosol compared to the control, the concentrations of the vitamin esters fell below 10%, but the alcoholic analogs remained at 30 to 40%. Despite equal dietary supply, in mink fed on Baltic herring, the hepatic levels of vitamin A1 were only about one-third of the values found in the smelt-fed mink. The organochlorines also altered hepatic lipid composition and impaired breeding and kit growth. In the kits of the females fed on Baltic herring, blood hemoglobin was decreased. [source] Male and Female Meadow Voles, Microtus pennsylvanicus, Differ in Their Responses to Heterospecific/Conspecific Over-MarksETHOLOGY, Issue 9 2010Christian T. Vlautin Voles use runways, paths, and trails that may also be used by rabbits and mink. These shared areas could contain the scent marks of conspecifics and heterospecifics. Thus, it is likely that the scent marks of heterospecifics may overlap or be overlapped by those of voles, forming over-marks. Much is known about how voles respond to over-marks of two different conspecifics. However, we do not know how they would respond to an opposite-sex conspecific whose scent marks are in an over-mark with the scent marks of predator or the scent marks of a non-predator heterospecifics. We tested the hypothesis that meadow voles, Microtus pennsylvanicus, differ in their response to the scent mark of the opposite-sex conspecific if the scent mark was overlapped by that of a mink, a vole predator, or rabbit, a vole non-predator. We found that female but not male voles showed a preference for the scent marks of the opposite-sex conspecifics that were part of the mink-vole over-mark when compared to those of opposite-sex conspecifics that were not part of the over-mark. This preference by female voles was independent of whether the male vole was the top-scent donor or bottom-scent donor of the over-mark. Male and female voles showed no preference between the scent marks of the opposite-sex conspecifics whose marks were part of or not part of the rabbit-vole over-mark. Sex differences in the manner that meadow voles respond to rabbit-vole and mink-vole over-marks are discussed. [source] The Smell of New Competitors: The Response of American Mink, Mustela vison, to the Odours of Otter, Lutra lutra and Polecat, M. putoriusETHOLOGY, Issue 5 2009Lauren A. Harrington We tested the response of wild American mink (an established alien species in the UK), to the odours of unfamiliar mink, European polecat and Eurasian otter. Polecats are similar in size and habits to mink, otters are larger than mink and a dominant competitor; both are native to the UK and both were absent during the original colonization by mink but are now undergoing natural population recoveries. The response of mink to experimental odours was assessed by counting the numbers of tracks (footprints) on rafts treated with anal gland secretions, and compared with response to a control raft, on two rivers in the Upper Thames valley, UK. Remote video showed that the number of tracks was positively correlated with the time that mink spent investigating an odour. We found that mink were attracted to the odours of both unfamiliar mink and polecats. There was little evidence that mink avoided the odour of otters. We suggest that, during an encounter with a polecat, mink may behave much as they would to a conspecific. We infer from the response of mink to the odour of otters, that, if mink do avoid otters, the mechanism of avoidance is likely to be complex, situation-dependent and perhaps affected by prior experience. [source] Chronic effects of polychlorinated dibenzofurans on mink in laboratory and field environmentsINTEGRATED ENVIRONMENTAL ASSESSMENT AND MANAGEMENT, Issue 2 2009Matthew J Zwiernik Abstract Mink are often used as a sentinel species in ecological risk assessments of chemicals such as polychlorinated biphenyls (PCBs), dibenzo- p -dioxins (PCDDs), and dibenzofurans (PCDFs) that cause toxicity mediated through the aromatic hydrocarbon receptor. Considerable toxicological information is available on the effects of PCBs and PCDDs on mink, but limited toxicological information is available for PCDFs. Thus, exposure concentrations at which adverse effects occur could not be determined reliably for complex mixtures in which PCDFs dominate the total calculated concentration of 2,3,7,8-tetrachlorodibenzo- p -dioxin equivalent (TEQ). Two studies were conducted to evaluate the potential toxicity of PCDFs to mink. The first was a chronic exposure, conducted under controlled laboratory conditions, in which mink were exposed to 2,3,7,8-tetrachlorodibenzofuran (2,3,7,8-TCDF) concentrations as great as 2.4 × 103 ng 2,3,7,8-TCDF/kg wet-weight (ww) diet or 2.4 × 102 ng TEQ2006-WHO-mammal/kg ww diet. In that study, transient decreases in body masses of kits relative to the controls was the only statistically significant effect observed. The second study was a 3-y field study during which indicators of individual health, including hematological and morphological parameters, were determined for mink exposed chronically to a mixture of PCDDs and PCDFs under field conditions. In the field study, there were no statistically significant differences in any of the measured parameters between mink exposed to a median estimated dietary dose of 31 ng TEQ2006-WHO-mammal/kg ww and mink from an upstream reference area where they had a median dietary exposure of 0.68 ng TEQ2006-WHO-mammal/kg ww. In both studies, concentrations of TEQ2006-WHO-mammal to which the mink were exposed exceeded those at which adverse effects, based on studies with PCDD and PCB congeners, would have been expected. Yet in both instances where PCDF congeners were the sole or predominant source of the TEQ2006-WHO-mammal, predicted adverse effects were not observed. Taken together, the results of these studies suggest that the values of the mammalian-specific toxicity equivalency factors suggested by the World Health Organization overestimate the toxic potency of PCDFs to mink. Therefore, hazard cannot be accurately predicted by making comparisons to toxicity reference values derived from exposure studies conducted with PCBs or PCDDs in situations where mink are exposed to TEQ mixtures dominated by PCDFs. [source] Yttrium oxide (Y2O3) as an inert marker in digestibility studies with dogs, blue foxes and mink fed diets containing different protein sourcesJOURNAL OF ANIMAL PHYSIOLOGY AND NUTRITION, Issue 9-10 2007S. G. Vhile Summary The study evaluated the use of yttrium oxide (Y2O3) as an inert marker in studies of apparent total tract digestibility in dogs, blue foxes and mink. Comparison was made with total faecal collection, and use of chromic oxide (Cr2O3) as marker respectively. Four experimental diets were added 0.1 g/kg yttrium oxide and 10 g/kg chromic oxide and fed to four animals of each species. Faecal recovery of yttrium oxide was 94.4% (SEM ± 1.0), and of chromic oxide 105.8% (SEM ± 1.5). The digestibilities of dry matter, crude protein, crude fat, starch and total carbohydrates obtained by total collection and yttrium oxide as marker showed close similarity, and in most cases not significant differences, independent of species and diets. In dogs, overall digestibilities of main nutrients with chromic oxide as marker were not significantly different from overall means obtained with yttrium oxide (p > 0.05). Overall digestibility of dry matter, crude protein and total carbohydrates in blue foxes and mink was significantly higher with chromic oxide than with yttrium oxide (p < 0.05). In dogs and blue foxes, digestibilities of individual amino acids determined by use of yttrium oxide were not different from values obtained using total collection of faeces, both within diets and for overall mean (p > 0.05). Overall amino acid digestibilities in dogs determined with chromic oxide as marker were similar to corresponding figures for yttrium oxide, whereas use of chromic oxide resulted in significantly higher digestibilites for a number of amino acids compared with yttrium oxide in foxes and mink (p < 0.05). The digestibilities of most main nutrients and amino acids revealed no interaction between diet and method (p > 0.05). The study showed that yttrium oxide can be used in low concentration in the feed, and allows high accuracy of analyses and thereby precise digestibility determination. It is concluded that yttrium oxide is an alternative inert marker to chromic oxide in the studied species. [source] Modelling space use and dispersal of mammals in real landscapes: a tool for conservationJOURNAL OF BIOGEOGRAPHY, Issue 4 2003David W. Macdonald Abstract Aim To explore the usefulness of Spatially Explicit Population Models (SEPMs), incorporating dispersal, as tools for animal conservation, as illustrated by the contrasting cases of four British mammals. Methods For each of the four species (American mink, Mustela vison, pine marten, Martes martes, dormouse, Muscardinus avellanarius and water vole, Arvicola terrestris) a spatial dynamics model was developed based on an integrated geographical information system (GIS) population model that linked space use to the incidence of the species. Each model had, first, a GIS, which stored environmental, habitat and animal population information, and secondly, an individual-based population dynamics module, which simulated home range formation, individual life histories and dispersal within the GIS-held landscape. Results The four models illustrated different interactions between species life-history variables and the landscape, particularly with respect to dispersal. As water voles and dormice occupy home ranges that are small relative to blocks of their habitat, they were most effectively modelled in terms of the dynamics of local populations within habitat blocks but linked by dispersal. In contrast, because the home ranges of American mink and pine marten are large relative to blocks of habitat, they were best modelled as individuals moving through a landscape of more or less useful patches of habitat. For the water vole, the most significant predictors of population size were the carrying capacity of each habitat and the annual number of litters. For the dormouse, the likelihood of catastrophe and the upper limit to dispersal movement were the key variables determining persistence. Adult mortality and home-range size were the only significant partial correlates of total population size for the American mink. Adult mortality was also a significant correlate of total population size in the pine marten, as were litter size and juvenile mortality. In neither the marten nor the mink was dispersal distance a significant factor in determining their persistence in the landscape. Main conclusions At a landscape scale it is difficult to measure animal distributions directly and yet conservation planning often necessitates knowledge of where, and in what numbers, animals are found, and how their distributions will be affected by interventions. SEPMs offer a useful tool for predicting this, and for refining conservation plans before irreversible decisions are taken in practice. [source] Testicular activity is restored by melatonin replacement after suprachiasmatic nucleus lesion or superior cervical ganglionectomy in minkJOURNAL OF PINEAL RESEARCH, Issue 1 2002Daniel L Maurel Subcutaneous melatonin implants were inserted in mink subjected to natural (autumn) or experimental gonadostimulatory short-days (4L:20D), after lesion of the suprachiasmatic nucleus (SCNx) or after superior cervical ganglionectomy (SCGx). Gonad stimulation was assessed by measuring testicular volume and plasma testosterone level. In SCNx and SCGx animals, all measurements were indicative of sexual quiescence. In contrast, both SCNx and SCGx animals with melatonin, maintained in natural or experimental gonadostimulating short-days, showed an increase in testicular activity 2 months after melatonin implantation. Thus, melatonin (and pineal activity) is a prerequisite for the photoperiodic stimulation of reproductive activity, and the SCN is not necessarily the target site for melatonin action on the renewal of reproduction in the mink. [source] Dioxin-like and non-dioxin like effects of polychlorinated biphenyls: Implications for risk assessmentLAKES & RESERVOIRS: RESEARCH AND MANAGEMENT, Issue 3 2002John P. Giesy Abstract Polychlorinated biphenyls (PCBs) are persistent, bioaccumulative and toxic contaminants in the environment. Individual PCB congeners exhibit different physicochemical properties and biological activities that result in different environmental distributions and toxicity profiles. The variable composition of PCB residues in environmental matrices and their different mechanisms of toxicity complicate the development of scientifically based regulations for risk assessment. Various approaches for the assessment of risks of PCBs have been critically examined. Recent developments in the toxic equivalency factor (TEF) approach for the assessment of toxic effects due to dioxin-like PCBs have been examined. The PCB exposure studies that describe non-dioxin-like toxic effects, particularly neurobehavioural effects and their effective doses in animals, were compiled. A comparative assessment of effective doses for dioxin-like and non-dioxin-like effects by PCBs has been made to evaluate the relative significance of non- ortho and ortho -substituted PCBs in risk assessment. Using mink as an example, relative merits and implications of using TEF and total PCB approaches for assessing the potential for toxic effects in wildlife were examined. There are several advantages and limitations associated with each method used for PCB risk assessment. Toxic effects due to coplanar PCBs occur at relatively smaller concentrations than those due to non-dioxin-like PCBs and, therefore, the TEF approach derives the risk assessment of PCBs in the environment. The need for the refinement of the TEF approach for more accurate assessment of risks is discussed. [source] Microsatellite markers for the endangered European mink (Mustela lutreola) and closely related mustelidsMOLECULAR ECOLOGY RESOURCES, Issue 6 2007M. T. CABRIA Abstract The European mink (Mustela lutreola L., 1761) is an endangered carnivore species whose populations suffered a severe decline during the last century. The genotyping of eight polymorphic microsatellite loci revealed a relatively low number of alleles per locus (two to eight), as well as low levels of polymorphism (observed and expected heterozygosity values per locus were 0.49 and 0.54, respectively). Cross-specific polymerase chain reaction amplifications were successful in seven closely related mustelid species suggesting that these loci may be useful not only for assessing genetic variability in European mink populations but also for determining potential hybridization events between M. lutreola and other mustelid species. [source] Predator,prey coupling: interaction between mink Mustela vison and muskrat Ondatra zibethicus across CanadaOIKOS, Issue 3 2009Nina Holmengen In this paper we explore variation in the predator-prey interaction between mink Mustela vison and muskrat Ondatra zibethicus across Canada based on 25 years of mink (predator) and muskrat (prey) data from the Hudson's Bay Company. We show that predator,prey interactions have stronger signatures in the west of Canada than in the east. In particular, we show that the observed phase plot trajectories of mink and muskrat rotate significantly clock-wise, consistent with predator,prey theory. We also investigate four phases of the mink muskrat interaction sequence (predator crash phase, prey recovery phase, etc.) and show that they are all consistent with a strong coupling in the west, whereas the presence of generalist predators and alternative preys can explain deviations from this pattern in the east. [source] Impact of released Eurasian otters on a population of American mink: a test using an experimental approachOIKOS, Issue 1 2004L. Bonesi Competition is considered to be a major evolutionary driving force within assemblages of related and morphologically similar species, but it is notoriously difficult to test and quantify especially amongst species that cannot be easily manipulated in a laboratory or in the field. By exploiting a re-introduction of Eurasian otters (Lutra lutra) in the Upper Thames catchment (UK) in 1999 we performed an experiment to test whether there was evidence of competition between otters and American mink (Mustela vison). Mink and otters are semi-aquatic mustelids belonging to the same guild. Otters are expected to be the dominant competitor because they are larger and better adapted at exploiting aquatic resources. Our hypothesis was that mink declines when the density of otters increases. We measured the effect of competition at the population level, by observing whether mink distribution and densities changed in an area of 1353 km2 in association with the arrival of its putative competitor. We estimated distribution and densities by means of sign surveys and trapping. The results showed that otters were associated with a significant and rapid reduction in the densities of mink, while mink occupancy remained approximately the same in an area of 2464 km2 that was used as a control. We observed that the spatial distribution of the mink population throughout its decline was influenced by the yearly cycle of mink activities, with areas being temporarily re-colonized during the dispersal season. Mink is an invasive species in the UK threatening the survival of some native species. Our findings suggest that the re-establishment of otter populations is likely to lead to a decline of mink that may, in turn, be beneficial to native species threatened by this invasive. [source] Competition between Eurasian otter Lutra lutra and American mink Mustela vison probed by niche shiftOIKOS, Issue 1 2004Laura Bonesi Interspecific competition is one of several constraints that might prevent an individual from maximising its energy intake. When an interspecific competitor is introduced, an individual is often forced to shift its diet according to the intensity of the competitive pressure. In this paper, we explore whether the introduced American mink (Mustela vison Schreber) shifts its diet when the density of its potential competitor, the Eurasian otter (Lutra lutra L.), is increased. We compared the diets of otter and mink at the same location but at two moments in time when the relative densities of these two species were different while controlling for the abundance of aquatic prey. Mink and otters are semi-aquatic mammals belonging to the same guild of mustelids and otters are expected to be the dominant competitor because they are larger and better at hunting underwater. The diets of otters and mink overlap to a great extent but while otters specialise mainly on aquatic prey, mink are able to exploit both aquatic and terrestrial prey. These observations prompted the hypothesis investigated in this work that at higher otter densities the diet of mink should change to include a higher proportion of terrestrial items. This hypothesis was supported by the data and at higher otter densities mink diet was observed to consist of a higher proportion of mammals and birds while fewer fish were present, although this pattern was present only in winter while no changes were observed in spring. Meanwhile the diet of otters remained basically unchanged. In the second part of the study, we investigated whether niche breadth and niche overlap between otter and mink changed at different otter densities. We found that niche overlap declined as the density of otters increased, in agreement with the prediction of habitat selection theory. [source] Spatial variation in mink and muskrat interactions in CanadaOIKOS, Issue 3 2001John Erb We investigated the spatial attributes of mink (Mustela vison) and muskrat (Ondatra zibethicus) interactions in Canada using 160 geographically paired historic time series of mink (n=80) and muskrat (n=80) harvest data obtained from Hudson's Bay Co. Archives. All series were 25 years in length (1925,1949) and were distributed primarily throughout five ecozones. We used autoregressive models and cross-correlation analysis to characterize the interactions between mink and muskrat. Model selection results did not differ among ecozones, and indicated that a predator-prey autoregressive model incorporating a delayed density-dependent term best described both the mink and muskrat harvest time series. Subsequent analysis of autoregressive coefficients and estimated lags indicated that mink and muskrat interactions vary throughout Canada. In western Canada, the trophic interactions appear to be strong, and mink population cycles lag behind muskrats 2,3 years. In central Canada, mink harvests lagged behind muskrats 1 year, and mink and muskrat interactions in central Canada, with the exception of the Hudson Plains ecozone, were intermediate. In eastern Canada, the trophic interactions appeared weakest, and there were no distinct time lags between mink and muskrat. Stronger interactions in western Canada may be a result of decreased prey diversity, forcing mink to specialize more on muskrats, whereas comparatively stronger perturbations stemming from other trophic interactions may alter the estimated interaction between mink and muskrat in eastern Canada. [source] Immunocytological analysis of meiotic recombination in the American mink (Mustela vison)ANIMAL GENETICS, Issue 2 2009P. M. Borodin Summary Using immunolocalization of MLH1, a mismatch repair protein that marks crossover sites along synaptonemal complexes, we estimated the total length of the genetic map, the recombination rate and crossover distribution in the American mink (Mustela vison). We prepared spreads from 130 spermatocytes of five male minks and mapped 3320 MLH1 foci along 1820 bivalents. The total recombination length of the male mink genome, based on the mean number of MLH1 foci for all chromosomes, was 1327 cM. The overall recombination rate was estimated to be 0.48 cM/Mb. In all bivalents, we observed prominent peaks of MLH1 foci near the distal ends and a paucity of them near the centromeres. This indicates that genes located at proximal regions of the chromosomes should display much tighter genetic linkage than physically equidistant markers located near the telomeres. [source] | |||||||||||||