Body size increase in insular rodent populations: a role for predators?

Insular mammalian populations living in areas of small size are often characterized by a drastic change in body mass compared to related continental populations or species. Generally, small mammals (less than 100 g) evolve into giant forms while large mammals (up to 100 g) evolve into dwarf forms. These changes, coupled with changes in other life, behavioural, physiological or demographic traits are referred to generally as the insular syndrome. We tested in this study the relative contribution of three factors — area of island, numbers of competitor species and number of predator species — to changes in body size of the woodmouse (Apodemus sylvaticus) in the Western Mediterranean Sea. Our results, based on a comparative analysis using the phylogenetic independent contrasts method, indicate that the increase in body size is related both to the decrease of island size and to the lower number of predator species. A decrease of competitor species does not seem to have an important effect.     

流行性出血热病毒在疫区鼠间垂直传播的首次证实

流行性出血热(EHF)病毒在鼠间垂直传播的问题一直未被证实。1985～1986年我们在实验研究的基础上进行了疫区现场研究,采用的基本方法是从感染的孕鼠子宫内剖取胎鼠,用免疫荧光法作抗原、抗体检查和病毒分离,结果从流行性出血热疫区捕获的4只黑线姬鼠孕鼠的胎鼠体内检出了特异性抗原和抗体(IgM和IgG)。从24只抗原阳性的褐家鼠孕鼠中检出抗原阳性胎鼠18只,垂直传播率达75％。从褐家鼠孕鼠和胎鼠中分离出病毒六株,经特异性试验和单克隆抗体鉴定确认为EHF病毒。上述事实证明,在自然条件下,流行性出血热病毒在疫区鼠类中存在着经胎盘感染或垂直传播。这一证实对于阐明疫源地形成、延续和扩散,以及人类发病等具有重要意义。     

云南姬鼠的蛋白多态性及其遗传分化关系

本文采用蛋白电泳技术对来源于云南省若干地区的姬鼠属（Ａｐｏｄｅｍｕｓ）的３种姬鼠──高山姬鼠（Ａ．ｃｈｅｖｒｉｅｒｉ）８只,中华姬鼠（Ａ．ｄｒａｃｏ）３只和大耳姬鼠（Ａ．ｌａｔｒｏｎｕｍ）１只,以及作为外群的同科的绒鼠属的大绒鼠（Ｈａｐａｌｏｍｙｓｄｅｌａｌｏｒｉ）３只进行了分析。共检测遗传座位２７个,发现２１个座位存在多态性。根据蛋白多态的数据对研究对象进行遗传分化关系的探讨,用系统分析软件ＰＨＹＬＩＰ计算它们之间的分化关系,得到了一棵无根系统树。结果表明,作为外群的大绒鼠明显不同于其它３种姬鼠而聚在最外面。８只高山姬鼠个体汇聚成独立的一支,中华姬鼠的３个个体也聚成一支,但大耳姬鼠却聚在中华姬鼠一支中,因此我们认为大耳姬鼠同中华姬鼠的分化时间可能比较晚近。     

Evolution of restriction sites of ribosomal DNA in natural populations of the field mouse,Apodemus speciosus

An analysis by restriction endonuclease digestion of ribosomal DNA (rDNA) was carried out in natural populations of Apodemus speciosus, a field mouse that is endemic to Japan. Two restriction sites, the EcoRI (E3) and DraI (D4) sites, in the nontranscribed spacer region downstream from the gene for 28S RNA showed polymorphism within and between individuals in the populations from the Japanese main islands. By contrast, populations from the small adjoining islands which are thought to have separated from the main islands 1–2 × 10⁴ years ago showed relatively low levels of polymorphism within and between individuals, i.e., one of the polymorphic bands in the case of each enzyme was predominant in these populations, irrespective of the variants. These results indicate that the rate of fixation of site variations depends on population size and that the direction of fixation is random. Furthermore, each polymorphic restriction site seems to be fixed independently.Correspondence to: H. Suzuki     

中国和韩国黑线姬鼠两亚种的线粒体DNA限制性片段分析

本文利用印迹杂交技术对中国华北地区黑线姬鼠Ａｐｏｄｅｍｕｓａｇｒａｒｉｕｓｐａｌｉｄｉｏｒ和韩国黑线姬鼠Ａ．ａｇｒａｒｉｕｓｃｏｒｅａｅ共１０７号标本的线粒体ＤＮＡ（ｍｉｔｏｃｈｏｎｄｒｉａｌＤＮＡ,ｍｔＤ－ＮＡ）,通过８种限制性内切酶的消化,进行了限制性片段的分析。共检出３５种限制性片段和１２种单倍体类型。１２种单倍型在平均离散度为１．０１％时聚合为两个亚群：一个亚群为黑线姬鼠华北亚种,由采自中国４个不同地区的５１号标本的４种单倍型所组成;另一个亚群为黑线姬鼠朝鲜亚种,由采自韩国４个不同地区的５６号标本的８种单倍型所组成。黑线姬鼠华北亚种和朝鲜亚种在ｍｔＤＮＡ表型上表现出一定差异,这在分子水平上确立了两亚种的分类地位。为了进一步澄清黑线姬鼠种下分类的混乱,很有必要对中国其他地区的标本进行该项研究     

气候因素对黑线姬鼠种群动态影响的非线性效应

受全球气候变化的影响,气候因素与害鼠种群变化之间的关系成为害鼠防治研究中的热点问题。以西安市长安区周边分布的黑线姬鼠为研究对象,通过标志重捕法进行种群动态监测,掌握其种群数量的动态变化规律,并结合非线性的统计方法广义可加模型,对该地区2015—2018年黑线姬鼠种群密度和气候因素数据进行分析,探讨该鼠种群变化与气候因素之间的关系。结果表明,该地区黑线姬鼠种群数量总体显现为下降趋势。黑线姬鼠种群密度存在显著的正向自我调节效应(F_(1.00, 5.77)=27.062,P0.01),且与上一月种群密度存在线性的正相关。当月平均温度与该鼠种群密度之间存在显著的非线性效应(F_(1.90, 5.77 )=4.696,P0.05),两者之间显现为钟型关系,当温度21℃时,两者之间显现为正相关,黑线姬鼠种群密度随温度的升高而升高,反之显现为负相关。当月累计降雨量与其种群密度之间也存在显著的非线性效应(F_(1.87, 5.77)=3.879,P0.05),同样,两者之间也显现为钟型关系,当降雨量90 mm时,两者之间显现为负相关,种群密度随降雨量的增加而降低,反之显现为正相关。因此,温度和降雨对黑线姬鼠种群变化具有调节作用,低温干旱和高温多雨均不适合该鼠的繁殖与生长。     

Supplemented nutrition decreases helminth burden and increases drug efficacy in a natural host–helminth system

Gastrointestinal (GI) helminths are common parasites of humans, wildlife, and livestock, causing chronic infections. In humans and wildlife, poor nutrition or limited resources can compromise an individual''s immune response, predisposing them to higher helminth burdens. This relationship has been tested in laboratory models by investigating infection outcomes following reductions of specific nutrients. However, much less is known about how diet supplementation can impact susceptibility to infection, acquisition of immunity, and drug efficacy in natural host–helminth systems. We experimentally supplemented the diet of wood mice (Apodemus sylvaticus) with high-quality nutrition and measured resistance to the common GI nematode Heligmosomoides polygyrus. To test whether diet can enhance immunity to reinfection, we also administered anthelmintic treatment in both natural and captive populations. Supplemented wood mice were more resistant to H. polygyrus infection, cleared worms more efficiently after treatment, avoided a post-treatment infection rebound, produced stronger general and parasite-specific antibody responses, and maintained better body condition. In addition, when applied in conjunction with anthelmintic treatment, supplemented nutrition significantly reduced H. polygyrus transmission potential. These results show the rapid and extensive benefits of a well-balanced diet and have important implications for both disease control and wildlife health under changing environmental conditions.     

云南4个地区高山姬鼠线粒体控制区种群遗传分化研究

对云南4个种群38个个体的线粒体控制区（D-loop）905 bp的核苷酸序列遗传变异进行分析,探讨了高山姬鼠种群遗传结构和分化。在905 bp D-loop基因的碱基序列中,共发现了57个变异位点（全变异的6.30%）,共定义了23个单倍型,其中有一个单倍型（Hap1）为横断山3个种群（中甸、丽江和剑川）所共享,其余22个单倍型均为各个种群所特有。分子变异分析（AMOVA）表明,种群间的遗传变异占33.7%,种群内的遗传变异占66.3%。FST统计结果表明,除昆明种群和横断山种群之间差异显著（P〈0.05）,其它地理种群间的差异均不显著（P〉0.05）,说明昆明种群与横断山种群之间出现了明显的遗传分化。