The mammalian magnetic sense is predominantly studied in species with reduced vision such as mole-rats and bats. Far less is known about surface-dwelling (epigeic) rodents with well-developed eyes. Here, we tested the wood mouse Apodemus sylvaticus for magnetoreception using a simple behavioural assay in which mice are allowed to build nests overnight in a visually symmetrical, circular arena. The tests were performed in the ambient magnetic field or in a field rotated by 90°. When plotted with respect to magnetic north, the nests were bimodally clustered in the northern and southern sectors, clearly indicating that the animals used magnetic cues. Additionally, mice were tested in the ambient magnetic field with a superimposed radio frequency magnetic field of the order of 100 nT. Wood mice exposed to a 0.9 to 5 MHz frequency sweep changed their preference from north-south to east-west. In contrast to birds, however, a constant frequency field tuned to the Larmor frequency (1.33 MHz) had no effect on mouse orientation. In sum, we demonstrated magnetoreception in wood mice and provide first evidence for a radical-pair mechanism in a mammal.
IntroductionSeveral mammalian species spontaneously align their body axis with respect to the Earth’s magnetic field (MF) lines in diverse behavioral contexts. Magnetic alignment is a suitable paradigm to scan for the occurrence of magnetosensitivity across animal taxa with the heuristic potential to contribute to the understanding of the mechanism of magnetoreception and identify further functions of magnetosensation apart from navigation. With this in mind we searched for signs of magnetic alignment in dogs. We measured the direction of the body axis in 70 dogs of 37 breeds during defecation (1,893 observations) and urination (5,582 observations) over a two-year period. After complete sampling, we sorted the data according to the geomagnetic conditions prevailing during the respective sampling periods. Relative declination and intensity changes of the MF during the respective dog walks were calculated from daily magnetograms. Directional preferences of dogs under different MF conditions were analyzed and tested by means of circular statistics.ResultsDogs preferred to excrete with the body being aligned along the North–South axis under calm MF conditions. This directional behavior was abolished under unstable MF. The best predictor of the behavioral switch was the rate of change in declination, i.e., polar orientation of the MF.ConclusionsIt is for the first time that (a) magnetic sensitivity was proved in dogs, (b) a measurable, predictable behavioral reaction upon natural MF fluctuations could be unambiguously proven in a mammal, and (c) high sensitivity to small changes in polarity, rather than in intensity, of MF was identified as biologically meaningful. Our findings open new horizons in magnetoreception research. Since the MF is calm in only about 20% of the daylight period, our findings might provide an explanation why many magnetoreception experiments were hardly replicable and why directional values of records in diverse observations are frequently compromised by scatter.
ABSTRACT:The afforestation of agricultural lands was carried out under different site and ecological conditions, including lower and medium elevated localities. The present study documents the rapidity of accumulation of surface layers and their characteristics in stands of Scots pine (Pinus sylvestris), Norway spruce (Picea abies), birch (Betula verrucosa) and Douglas fir (Pseudotsuga menziesii) in the territory of the Training Forest Enterprise in Kostelec nad Černými lesy, at the altitude 430 m a.s.l., on the site of nutrient-poor gleyed soils. The plots were compared with the neighbouring continuously forested site covered with old pine-spruce stand and with near-situated arable field. During the first roughly 40 years, considerable changes were documented on the afforested plots. Forest-floor humus layers in the coniferous stands have already been formed, the humus forms being more favourable compared with the old forest site. Acidification and loss of nutrients run in the upper mineral horizons. These processes were also responsible for the less favourable character of the forest soil in the old stand. Birch showed minor shifts of soil properties in the mineral horizon compared to the conifers; the surface humus accumulation was not observed there yet. The lowest degradation among conifers was shown in Douglas fir, intensively taking up deficient nutrients on the other hand.
The venison is popular for many properties that make it unique, for example, low intramuscular fat (IMF) content, good nutrition and sensory properties. The aim of this study was to determine the difference between sex in carcase traits, chemical and fatty acid composition in different body parts. The meat analysis was performed in 9 stag and 9 doe individuals from the farm breeding in Mokrovraty in Czech Republic. The analysis was carried out on the basis of samples taken from the carcases of fallow deer. Chemical analysis of meat from musculus longissimus lumborum et thoracis (MLLT), musculus semimembranosus (MS) and musculus serratus ventralis (MSV) was performed. The fatty acid analysis was measured in MLLT. Most of the measured carcase weight parameters show sexual dimorphism, however no effect on percentage of main meat parts was detected. From chemical meat composition, the dry matter content was higher (p < .001) in stags compared to does as well as crude protein (p¼ .017). IMF content was not affected by sex. When compare chemical composition of muscles, MLLT and MS had higher dry matter (p¼ .004), ash (p < .001) and lower protein content (p¼ .011) compared to MSV. The fatty acid analyses showed, that stags had significantly higher content of myristic (C14:0; p¼ .015), pentadecanoic (C15:0; p¼ .008), palmitic (C16:0; p¼ .024), margaric (C17:0; p¼ .009) and myristoleic acid (C14:1c9; p¼ .001) in MLLT than does. Sex had no effect on the sums and ratios of fatty acids and atherogenic and thrombogenic index (TI). In conclusion, sex affected mainly weight of carcase and the chemical meat composition.
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