Neural correlates of behavioral gap detection in the inferior colliculus of the young CBA mouse

The gap detection paradigm is frequently used in psychoacoustics to characterize the temporal acuity of the auditory system. Neural responses to silent gaps embedded in white-noise carriers, were obtained from mouse inferior colliculus (IC) neurons and the results compared to behavioral estimates of gap detection. Neural correlates of gap detection were obtained from 78 single neurons located in the central nucleus of the IC. Minimal gap thresholds (MGTs) were computed from single-unit gap functions and were found to be comparable, 1–2 ms, to the behavioral gap threshold (2 ms). There was no difference in MGTs for units in which both carrier intensities were collected. Single unit responses were classified based on temporal discharge patterns to steady-state noise bursts. Onset and primary-like units had the shortest mean MGTs (2.0 ms), followed by sustained units (4.0 ms) and phasic-off units (4.2 ms). The longest MGTs were obtained for inhibitory neurons (xˉ = 14 ms). Finally, the time-course of behavioral and neurophysiological gap functions were found to be in good agreement. The results of the present study indicate the neural code necessary for behavioral gap detection is present in the temporal discharge patterns of the majority of IC neurons. Accepted: 6 February 1997     

Behavioural discrimination among chromosomal races of the house mouse (Mus musculus domesticus)

This work is concerned with the extent of behavioural discrimination between three chromosomal races of the house mouse (the standard 40-chromosome race and a 32- and 36-chromosome races) found in the vicinity of a hybrid zone in northern Scotland. Mice were investigated for several elements of their social behaviour. Within-population dyadic encounters did not show consistent behavioural differences attributable to karyotype among five populations (two standard race, two 36-chromosome race, one 32-chromosome race). Between-population dyadic encounters revealed significant differences between three populations. The standard population examined appeared to be the most “open” to foreigners, the 32-chromosome population the most “closed” while the 36-chromosome mice displayed an intermediate response. Differences in behaviour displayed during between-population as compared to within-population dyadic encounters revealed the occurrence of behavioural discrimination between populations. The implication of these results on the dynamics of the hybrid zone are discussed.     

Morphometric variation in nearly unstudied populations of the most studied mammal: The non-commensal house mouse (Mus musculus domesticus) in the Near East and Northern Africa

The phenotypic consequences in the house mouse (Mus musculus domesticus) of the transition from an ordinary field-dwelling rodent to a species that is dependent on human populations was studied by investigating the morphometric variation of non-commensal populations of M. m. domesticus from Syria, Jordan, SW Iran, and Libya and comparing them with that of conspecific commensal populations from Eastern Turkey, Greece, and Bulgaria. Commensal populations of M. musculus musculus from the Czech Republic were used as an outgroup. About 849 adult specimens of M. musculus were analysed by multivariate procedures based on standard molar, skull and body measurements. As expected, there was considerable variation among the studied populations and a good correspondence between morphometric and geographic distances. The resulting morphometric tree was consistent with the hypothesis that the original radiation of M. m. domesticus took place somewhere in the Near East. Commensal populations of M. m. domesticus form a single derived branch. Specimens originating from four different sites in eastern Syria showed the greatest similarity to one another and possessed relatively bigger molars than the other studied populations. Commensal populations were characterised by longer tails when compared to non-commensal populations, which suggests an adaptation for living in a more three-dimensionally heterogeneous environment for commensal populations.     

MAMMIFRES DE SANSAN,coordinated by Stéphane Peigné and Sevket Sen, 2012. Mémoires du Muséum National d'Histoire naturelle,Publication Scientifi que 203, 709 pages,ISBN 978-2-85653-681-0.Mammifères de Sansan,key volume on a historical locality

正The Muséum National d’Histoire naturelle,via the able hands of Stéphane Peignéand Sevket Sen,has produced a massive scientific work that compiles advanced studies on the diverse mammalian fossil assemblage of Sansan,Gers,southwestern France.Servais et al.(2012)called Sansan a"lagersttte",and so it is:a remarkable fossil site that assembles much of the biota of its past community in one place.Sansan is a site complex with adjacent     

The house mouse: a model and motor for evolutionary understanding

Commensal house mice have spread from their probable origin in north India, differentiating into a number of forms described variously as species, semispecies or subspecies. The different taxa can breed together and exchange genes but they retain their distinctiveness (although Mus ( musculus ) molossinus of Japan seems to be the result of a complete fusion between M.  ( m .)  musculus and M.  ( m .)  castaneus ). The most widespread form is M.  ( m. )  domesticus , which has successfully colonized every continent as a commensal, albeit with varying contributions from other Mus genomes. It has also been domesticated as the laboratory mouse. This means that the same genome is exposed to a wide variety of environments and gives tremendous opportunities for exploring the operation of different evolutionary mechanisms. Mice have accompanied evolutionary understanding from early Darwinian days – confirming Mendelian ratios and showing they applied in mammals, providing data on rates of evolution, and representing examples of dominance modification, differential survival, competition and other indicators of a struggle for existence. However, they have an unfulfilled potential to drive as well as to illuminate evolutionary theory – by revealing more about, for example, the interactions between gene flow and social determinants, constraints on introgression and physiological adjustments. This potential can be explored through our ever-deepening knowledge of the genome and molecular mechanisms, and by the application of new techniques, but its most effective agent will always be the cross-disciplinary synergy of visionary scientists like Julian Huxley, Charles Elton and Louis Thaler.  © 2005 The Linnean Society of London, Biological Journal of the Linnean Society , 2005, 84 , 335–347.     

An assessment of time-dependent effects of lead exposure in algerian mice (Mus spretus) using different methodological approaches

Time-dependent effects of lead (Pb) toxicity were studied in Algerian mice (Mus spretus) treated with Pb acetate via drinking water (1 g Pb acetate/L) for different periods of exposure (15, 45, and 90 d). End points included the determination of hepatic Pb concentration and the assessment of some morphophysiological, biochemical and cytogenetical parameters. A control group receiving distilled water was also monitored for comparative purposes. Hepatic Pb accumulation increased with the time of exposure and was significantly higher in treated mice when compared to controls. In association with significant body mass loss in Pb-exposed mice, for 15 and 45 d, a significant increase in the relative spleen mass was observed after 45 d of intoxication. Pb-exposed mice also showed significant decreases in red blood cells, hematocrit, and mean corpuscular hemoglobin. On the contrary, changes in plasma transferases (aspartate aminotransferase and alanine aminotransferase) and hepatic superoxide dismutase activities did not reach statistical significance. A significant increase in the frequency of micronucleated polychromatic bone marrow erythrocytes was also found in the 90-d-exposed mice, compared to nontreated mice and the other exposed groups. Exposure to Pb acetate resulted also in a slight time-dependent decrease of the polychromatic-normochromatic ratio. These results support the concept that a long-term chronic exposure to Pb induced alterations upon some morphophysiological and genetic paramaters in Algerian mice.     

‘Anticipatory’ reproduction by small mammals cannot succeed without enhanced maternal access to protein food

The belief seems to be persisting and spreading that some animals can use an unknown environmental cue to anticipate a future supply of food that would support a greatly increased number of their maturing young, and proceed to prolifically and successfully produce such young before they have access to a supply of protein food that would support that enhanced productivity. This is not biologically possible. To sustain the successful gestation and subsequent growth of young, a female must have access to a sufficient source of protein food. There is evidence to suggest that this necessary supply of protein is present in the environment of those that exhibit this apparently anticipatory reproduction, but researchers have either not looked for it, or not found it. The confirmation of the existence of such food would not only explain the ‘anticipatory’ breeding, but would remove the need to postulate the presence of unknown environmental cues.     

The role of biogeography in shaping diversity of the intestinal microbiota in house mice

The microbial communities inhabiting the mammalian intestinal tract play an important role in diverse aspects of host biology. However, little is known regarding the forces shaping variation in these communities and their influence on host fitness. To shed light on the contributions of host genetics, transmission and geography to diversity in microbial communities between individuals, we performed a survey of intestinal microbial communities in a panel of 121 house mice derived from eight locations across Western Europe using pyrosequencing of the bacterial 16S rRNA gene. The host factors studied included population structure estimated by microsatellite loci and mitochondrial DNA, genetic distance and geography. To determine whether host tissue (mucosa)‐associated communities display properties distinct from those of the lumen, both the caecal mucosa and contents were examined. We identified Bacteroides, Robinsoniella and Helicobacter as the most abundant genera in both the caecal content and mucosa‐associated communities of wild house mice. Overall, we found geography to be the most significant factor explaining patterns of diversity in the intestinal microbiota, with a comparatively weaker influence of host population structure and genetic distance. Furthermore, the influence of host genetic distance was limited to the mucosa communities, consistent with this environment being more intimately coupled to the host.     

中国地鼠线粒体DNA 16S rRNA基因序列分析及分子系统发育研究

目的通过克隆分析中国地鼠16S基因的部分序列,对中国地鼠16S基因的结构和功能进行初步探索和揭示。方法从GenBank中已报道的啮齿动物16S基因保守区设计一对引物,进行PCR扩增,测序。用Blastn与GenBank中七种啮齿类动物的16S基因进行序列比较,分析其碱基组成及变异情况,并用邻接法(NJ)、非加权组平均法(UPGMA)构建分子系统树,在分子水平上探讨中国地鼠和其他啮齿类动物的进化关系,对中国地鼠的种属地位进行了进一步验证。结果获得了中国地鼠线粒体16S基因的部分序列,其碱基组成A、T、C、G分别为40.5%、24.5%、18.7%、16.3%,与其他七种啮齿类动物的碱基含量相比,各碱基含量基本相似。NJ进化树表明,中国地鼠、金黄地鼠与欧洲仓鼠先聚为一支,小鼠与大鼠先聚为一支,东方田鼠、台湾田鼠与东欧田鼠先聚为一支。结论中国地鼠和金黄地鼠的亲缘关系最近,与传统的分类地位基本吻合。