Duplication of J κ genes within genus Rattus

We have isolated a region containing the immunoglobulin kappa chain joining segments from a liver DNA library of the Australian rat Rattus villosissimus, and determined its nucleotide sequence. While the laboratory rat (Rattus norvegicus) had previously been shown to contain three recently duplicated copies of J 2, R. villosissimus has only two. Furthermore, all three copies of J 2 in R. norvegicus share an 11 by deletion in their 5 flanking regions which is not evident in either copy of J 2 in R. villosissimus. This suggests that the initial duplication events occurred separately in the two lineages, and were followed by a second duplication in R. norvegicus, all three duplications having occurred within the last 6–12 million years (although more complicated schemes involving gene conversion events cannot be excluded). These results indicate that there is a high degree of plasticity in this region of the genome, and that selective forces must exist which have maintained the number of expressible J segments in humans (5) and rodents (4–6) within their narrow range.     

A mathematical epidemiological model of gram-negative Bartonella bacteria: does differential ectoparasite load fully explain the differences in infection prevalence of Rattus rattus and Rattus norvegicus?

We postulate that the large difference in infection prevalence, 24% versus 5%, in R. norvegicus and R. rattus, respectively, between these two co-occurring host species may be due to differences in ectoparasite and potential vector infestation rates. A compartmental model, representative of an infectious system containing these two Rattus species and two ectoparasite vectors, was constructed and the coefficients of the forces of infection determined mathematically. The maximum difference obtained by the model in the prevalence of Bartonella in the two Rattus species amounts to 4.6%, compared to the observed mean difference of 19%. Results suggest the observed higher Bartonella infection prevalence in Rattus norvegicus compared to Rattus rattus, cannot be explained solely by higher ectoparasite load. The model also highlights the need for more detailed biological research on Bartonella infections in Rattus and the importance of the flea vector in the spread of this disease.     

Rattus exulans and the catastrophic disappearance of Hawai’i’s native lowland forest

Paleoenvironmental and archaeological investigations from the ’Ewa Plain of O’ahu provide insight into the problem of understanding lowland native forest loss in Hawai’i. Data from pollen analysis of a pond core record, avian paleontology, and archeology, document a precipitous decline of the native forest starting before Polynesian settlement on the ’Ewa Plain but after Polynesian colonization of O’ahu. It is hypothesized that rats, introduced by Polynesian colonizers, increased exponentially in the absence of significant predators or competitors, feeding on a largely endemic vegetation that had evolved in the absence of mammalian predators. Rats radiated ahead of human colonizers on O’ahu, eating their way through the vegetation, perhaps before the colonizers had encountered much of the pristine lowland forest into which the rats had radiated. This hypothesis is supported by several observations, including the almost complete absence of extinct or extirpated avian faunal remains in archaeological deposits, the present distribution of endemic vegetation in Hawai’i, rat ecology, population biology, and other evidence.

α2u-globulins mediate manipulation of host attractiveness in Toxoplasma gondii–Rattus novergicus association

Uninfected female rats (Rattus novergicus) exhibit greater attraction to the males infected with protozoan parasite Toxoplasma gondii. This phenomenon is contrary to the aversion towards infected males observed in multitude of other host–parasite associations. In this report, we describe a proximate mechanism for this anomaly. We demonstrate that T. gondii infection enhances hepatic production and urinary excretion of α2u-globulins in rats. We further demonstrate that α2u-globulins are sufficient to recapitulate male sexual attractiveness akin to effects of the infection. This manipulation possibly results in greater horizontal transmission of this parasite between the infected male and the uninfected female. It supports the notion that in some evolutionary niches parasites can alter host sexual signaling, likely leading to an increased rate of sexual transmission.Upon infection, Toxoplasma gondii invades immune-privileged organs of male rats like brain and testes. Ensuing chronic infection causes change in the behavior of the infected rats, namely: (a) loss of aversion to cat odors (Berdoy et al., 2000; Vyas and Sapolsky, 2010) and (b) gain of enhanced sexual attractiveness (Dass et al., 2011; Vyas, 2013). These changes plausibly lead to greater transmission of the parasite by trophic route to the cat intestine and by sexual route to female rats, although incontrovertible evidence of greater transmission in field conditions is not yet available (Worth et al., 2013). Correlative suggestions have also been made about increased attractiveness of infected human males and sexual transmission in humans (Hodkova et al., 2007; Flegr et al., 2014), although definitive evidence is presently unavailable. The gain in attractiveness post infection is particularly interesting because parasitism is generally observed to reduce sexual attractiveness of the host across varied phylogenies (Hamilton and Zuk, 1982; Folstad and Karter, 1992; Kavaliers et al., 2005). In this report, we investigate the proximate mechanism of this paradoxical effect.We first determined preference of uninfected estrus females for urine marks from control and infected males in an approach–approach conflict assay (detailed methods are described in Supplementary Information). Females spent greater time in bisect containing urine from the infected males (8/11 females, control < infected). For each second spent in the vicinity of urine from control males, receptive females spent 2.12 s with the infected male urine (paired t-test: |t₁₀|=2.78, P=0.019). Subsequently, female preference for low- and high-molecular weight fractions of the urine was separately quantified (LMW and HMW, respectively; cutoff=3 kDa). Volatiles bound to HMW fraction were displaced by a competitive molecule, menadione (Papes et al., 2010). Volatiles in HMW fractions before and after menadione displacement were compared with vehicle using direct analysis in real-time mass spectrometry (DART-MS). This analysis indicated the absence of any bound volatiles in displaced samples used for behavioral measurements. Analysis of variance (ANOVA) revealed significant interaction between infection status and the fractions (F_(1,30)=8.23, P=0.007). Females exhibited comparable preference to the LMW fraction of control and infected males (Figure 1a; control: 387±47 s, infected: 398±35 s; paired t-test: |t₁₅|=0.22, P>0.8; statistical power=0.054). In contrast, HMW fraction of the infected male was significantly preferred over that of control males (Figure 1a; control: 282±20 s, infected: 457±26 s; |t₁₅|=4.84, P<0.001). HMW fraction of infected animals exhibited greater attractiveness even when grafted on control LMW fraction (Figure 1b; control: 317±25 s, infected: 493±34 s; |t₁₁|=3.09, P=0.01). The majority of urinary proteins in the HMW fraction were determined to be α2u-globulins through mass spectrometric analysis (LOC259246 and LOC298109). Proteins homologous to rat α2u-globulins are also involved in chemical communication in mice (Hurst, 2009; Papes et al., 2010; Vasudevan and Vyas, 2013), including sexual signaling (Roberts et al., 2010).Open in a separate windowFigure 1The greater attractiveness of T. gondii-infected males was communicated by HMW, and not LMW, fraction of the male urine. Estrus females exhibited greater attraction to HMW fraction of the urine obtained from the infected males (a, black dots). N=16 females. ANOVA: P=0.514 for fractions; P=0.018 for infection status; P=0.007 for interaction. Abscissa and ordinate depict time spent in bisect containing urine from infected or control animals, respectively (in second, trial duration=1200 s). Solid circles depict data obtained from individual females. Gray diagonal line depicts chance (abscissa=ordinate). The attraction was not recapitulated by LMW fraction (<3 kDa) of the urine (a, gray dots). HMW obtained from infected animals was attractive to females even when combined with LMW of control urine (b). N=12 females. Mass spectroscopic analysis revealed major component of HMW fraction to be α2u-globulins.Infected animals contained greater amounts of α2u-globulin mRNA and protein in liver (Figures 2a and b). Congruently, urine from infected animals contained greater amounts of α2u-globulins (Figure 2b, 138% increase; P=0.011). In both liver and urine, the 25th percentile of α2u-globulin quantity in infected animals surpassed the 75th percentile of respective controls. α2u-globulins levels in preputial glands did not significantly differ between control and infected males (P=0.37).Open in a separate windowFigure 2Toxoplasma gondii infection increased α2u-globulins production in liver and excretion in urine. Infection enhanced α2u-globulins mRNA abundance in the liver (a). Ordinate depicts PCR cycles needed to reach a threshold when using α2u-globulins primers minus when using GAPDH primers (a housekeeping gene). Box plot depicts median, 25th percentile and 75th percentile. *P<0.05; exact Mann–Whitney test. N =7. Liver and urine from infected animals contained greater amounts of α2u-globulin protein. N=6 control, 8 infected (liver); N=7 (urine) (b). Ordinate depicts densitometric intensity, normalized to intensity of a pooled sample run in the same gel. Same pooled samples were used in all gels of the experiment. Creatinine-adjusted urine samples were used. Both groups exhibited comparable filtration rates of urine from the kidney (creatinine content; P>0.9) and a comparable tendency to place urine marks in a novel arena (P>0.9). *P<0.05 and **P<0.01; exact Mann–Whitney test. N=7. Renatured α2u-globulins postdialysis were sufficient to recapitulate greater attractiveness (c). Females exhibited attraction to FPLC-purified HMW fraction containing α2u-globulins, even after its denaturation in 3 m guanidinium chloride, subsequent dialysis and then renaturation in buffered physiological saline to remove all bound volatiles. N=12 females.Volatile substances in urine are known to bind α2u-globulins. The observation that HMW fraction from urine of infected animals was able to retain greater attractiveness even after menadione displacement supports the notion that α2u-globulins rather than volatiles bound to it were the active ingredients. We conducted a further experiment to test the possibility of residual volatiles still being bound to α2u-globulins in amounts undetectable by DART-MS. The fast protein liquid chromatography (FPLC)-purified α2u-globulins fraction was denatured, dialyzed and transferred to physiological buffer for renaturation. Dialysis with excess buffer was used in an intervening part of the cycle to remove any residual volatiles. Renaturation was confirmed by circular dichroism and tryptophan imaging. This procedure failed to rescue female attractiveness. Females exhibited robust preference to dialyzed α2u-globulins (Figure 2c; 10/12 females; |t₁₁|=4.09, P=0.002). Moreover, females exhibited clear preference for a greater concentration of FPLC-purified α2u-globulins in two-choice preference task comparing low and high doses (5 μg μl⁻¹: 334±41 s, 1.66 μg μl⁻¹: 208±24 s; paired t-test: |t₁₀|=2.78, P=0.014). These observations suggest that α2u-globulins can signal attractiveness without necessity of volatiles and in a dose-dependent manner. This is consistent with ability of HMW urinary fraction from the infected animals to evoke greater attraction, coupled with greater production of α2u-globulins postinfection. In other words, T. gondii infection increases urinary excretion of α2u-globulins, and greater α2u-globulins in the infected urine is sufficient to signal greater attractiveness. Greater α2u-globulins production in the infected rats is congruent with the observations that these proteins require testosterone for synthesis and that T. gondii infection increases testosterone production in male rats (Kulkarni et al., 1985; Lim et al., 2013).Many models of sexual selection posit that male sexual advertisement is an ‘honest'' proxy of an ability to fight infections. This honesty is thought to arrive because resources used for sexual advertising produce a handicap in ability to fight parasites or pathogens (Hamilton and Zuk, 1982; Wingfield et al., 1997). In other words, sexual signals are expensive to produce or maintain, thus allowing only fit males to engage in the advertisement. Many parasites do exploit host sexual signals. More frequently, this exploitation takes the form of either eavesdropping on sexual signals to find a new host or to inter-species mimicry of sexual signals by parasites to attract a potential host (Zuk and Kolluru, 1998; Haynes and Yeargan, 1999; Zuk et al., 2006). Parasites in these cases do not influence host advertisement per se. In this backdrop, rat–T. gondii association provides additional plausibility of the parasites changing magnitude of host sexual advertisement.Parasites are known to affect the behavior of their hosts (Hughes et al., 2012). This observation is frequently employed to argue that natural selection acts on genes and not necessarily individuals. In this narrative, the body of the host becomes an extended phenotype of the parasite (Dawkins, 1999; Hunter, 2009) and the behavioral changes correlate with increased transmission of the parasite. T. gondii has earlier been shown to increase sexual attractiveness of the infected males, resulting in greater sexual transmission of the parasite (Dass et al., 2011). Current observations present a molecular mechanism for T. gondii-induced extended phenotype.     

Genetically Controlled Variation of "Acid" β-Galactosidase Detected in Rattus norvegicus by Isoelectric Focusing

Two genetically variant forms of rat "acid" beta-galactosidase were found to differ in isoelectric point and pH dependence, but not in thermostability or sensitivity to inhibition by p-mercuribenzoate (PMB). The results of two backcrosses and an intercross indicated that the isoelectric focusing phenotypes are controlled by two codominant alleles at a single autosomal locus, for which we propose the name Glb-1. No significant linkage between Glb-1 and albino (LG I), brown (LG II), or hooded (LG VI) was observed. Strain-specific differences in total levels of kidney beta-galactosidase were detected, but it is not yet known whether the variation is controlled by genes linked to Glb-1. Experiments in which organ homogenates were incubated with neuraminidase indicated that the genetically variant forms do not result from differences in sialylation, though sialylation does appear to be largely responsible for the presence of multiple bands within each phenotype and for differences in the banding patterns of beta-galactosidases derived from different organs. The beta-galactosidase present in the bands used for Glb-1 typing resembles human GM1 gangliosidase (GLB1) with respect to pH optimum, substrate specificity, and susceptibility to inhibition by PMB. It also appears that Glb-1 is homologous with the Bgl-e locus of the mouse. In rats as in mice the genetically variant bands of beta-galactosidase are active at acid pH and have relatively high isoelectric points. In both species these bands are readily detectable in kidney homogenates, and can be revealed in homogenates of liver or spleen following treatment with neuraminidase. The presence of the same beta-galactosidase bands in homogenates of rat kidney and small intestine as well as in neuraminidase-treated homogenates of liver and spleen suggests that the Glb-1 variants differ by one or more point mutations in the structural gene for "acid" beta-galactosidase.     

Something old,something new: do genetic studies of contemporary populations reliably represent prehistoric populations of Pacific Rattus exulans?

Through our research focusing on genetic studies of both ancient and extant commensal animals in the Pacific for addressing issues of population origins and mobility in the region, we have been able to process a large number of archaeological faunal remains that we can compare to modern samples from the same islands. These comparisons shed light on and provide specific evidence for Rattus exulans population change through time. This information may provide a model for understanding human populations in the region and will illustrate the complexities of using data obtained from modern populations to infer prehistoric relationships. Two case studies are presented here-analyses of modern and archaeological populations of R. exulans from both Chatham Island and New Zealand. These two cases provide very different pictures regarding the relationship between the archaeological and the extant populations.     

Chromosome evolution in Australian Rattus — G-banding and hybrid meiosis

The karyotypes of seven species of Australian Rattus were studied by G-banding. When taken in conjunction with molecular data, it is shown that rate of chromosome evolution in the R. sordidus group (R. sordidus, R. villosissimus and R. colletti) has been remarkably rapid and directed entirely towards changes of the Robertsonian type. From data on hybrid fertility it is concluded that the presence of fusions with monobrachial homology contributes more to reduced fertility than fusions per se or genetic differences.     

我国大家鼠(Rattus norvegicus Berkenhout)的亚种分化

大家鼠在国内的亚种分化迄今并未定论,争议的焦点主要反映在:1)socer与caraco等亚种如何划分。Allen(1940)将从河北至甘肃,四川,云南,福建的大家鼠视为scoer。Ellerman et al.(1951)却认为除福建外我国大陆上的大家鼠均属caraco,而socer则为异名;2)东南部的大家鼠,Howell(1929)认为广州、厦门、福建标本应订socer;Allen(1940)也将福建标本订为 socer,但指出东南部大家鼠值得进一步研究;Ellerman et al.(1951)和Dan Van Tien(1966)却都主张福建、广东标本应属norvegicus;3)海南岛的大家鼠尚未订亚种(黑田长礼,1940)。 本文所用标本473号,成体和亚成体,随机取自全国23个省区,各省区标本数目分别列于表1。用数理统计方法对比不同类群间的性状差异,从而研究其地理变异性。     

Feeding Habits of Introduced Black Rats,Rattus rattus,in Nesting Colonies of Galapagos Petrel on San Cristóbal Island,Galapagos

Introduced rodents are responsible for ecosystem changes in islands around the world. In the Galapagos archipelago, their effects on the native flora and fauna are adverse, including the extinction of endemic rodents in some islands and the reduction in the reproductive success of the Galapagos petrel (Pterodroma phaeopygia) in its nesting zones. Understanding the feeding behavior of introduced rodents and their trophic interactions with native and non-native species on islands, can assist in the design of management strategies and conservation plans of invasive and endemic species respectively. Four petrel nesting colonies were monitored during June 2013 on San Cristóbal Island (El Plátano, El Junco, San Joaquín, and La Comuna). The feeding habits of black rats were evaluated by analyzing stomach contents and stable isotopes in hair. Three species of introduced rodents were captured. R. rattus was the most abundant at all sites (n=43, capture success (CS) = 55.8%), followed by the house mouse, Mus musculus (n = 17, CS = 37.8%), and the Norwegian rat, R. norvegicus (n = 4, CS = 4.5%), captured only at La Comuna. The omnivorous black rat ate mostly plants (98%) and arthropods (2%). Intact seeds of Miconia robinsoniana were the main food at all sites (relative abundance=72.1%, present in 95% of the analyzed stomachs), showing the black rats’ possible role in the archipelago as endemic seed dispersers. There was no evidence of petrel’s intake; however, its possible consumption is not discarded at all. The δ¹⁵N and δ¹³C analysis corroborated the primarily herbivorous diet of black rats. The isotopic signatures of the three rodent species reflect the inter- and intra-specific differential use of food resources. Black rat showed a wider diet in La Comuna, which was related to a lower availability of its primary prey and its ability to adapt to the available resources in its habitat.     

Stage of the Estrous Cycle Does Not Influence Myocardial Ischemia–Reperfusion Injury in Rats (Rattus norvegicus)

Even though cardiovascular disease is the leading cause of death for men and women, the vast majority of animal studies use male animals. Because female reproductive hormones have been associated with cardioprotective states, many investigators avoid using female animals because these hormones are cyclical and may introduce experimental variability. In addition, no studies have investigated the specific effects of the estrous cycle on cardiac ischemic injury. This study was conducted to determine whether the estrous cycle stage influences the susceptibility to ischemic injury in rat hearts. Estrous cycle stage was determined by using vaginal smear cytology, after which hearts underwent either in vivo (surgical) or ex vivo (isolated) ischemia–reperfusion injury. For in vivo studies, the left anterior coronary artery was ligated for 25 min of ischemia and subsequently released for 120 min of reperfusion. Infarct sizes were 42% ± 6%; 49% ± 4%; 40% ± 9%; 47% ± 9% of the zone-at-risk for rats in proestrus, estrus, metestrus, and diestrus, respectively. For ex vivo studies, isolated, perfused hearts underwent global ischemia and reperfusion for 25 and 120 min, respectively. Similar to our in vivo studies, the ex vivo rat model showed no significant differences in susceptibility to infarction or extent of cardiac arrhythmia according to estrous stage. To our knowledge, these studies provide the first direct evidence that the stage of estrous cycle does not significantly alter cardiac ischemia–reperfusion injury in rats.Abbreviations: VF, ventricular fibrillation; VT, ventricular tachycardiaCardiovascular disease remains the leading cause of morbidity and mortality throughout the industrialized world, with ischemic heart disease being a major manifestation of cardiovascular disease. Many investigators use animal models to advance our understanding of the etiology and mechanisms involved. Although ischemic heart disease is the leading cause of death for both men and women, the overwhelming majority of studies use male animals. Perhaps the most common reason for this practice is that physiologic fluctuations in female reproductive hormones such as estrogen may be a confounding variable, given the influence of female reproductive hormones on various organ systems.²⁵ Despite the assertion that cyclical variations in female reproductive hormones may confound experimental studies, few data are available that support estrous-cycle–dependent variations in susceptibility to ischemic heart injury.Epidemiologic studies suggest that, compared with men, women have lower cardiac mortality prior to undergoing menopause.⁴⁰ Consistent with human studies, experimental models in several species commonly show that the degree of cardiac injury in young female animals is lower than that in male counterparts.^7,9,21,22,42 Exogenous administration of estrogen has a clear effect in reducing injury,^14,15 but whether endogenous cyclical variations in female reproductive hormones affect cardiac injury is not known.Rats and mice are commonly used species to examine cardiac ischemia–reperfusion injury. Unlike humans, rodents do not undergo menstruation, during which the uterine endometrium sloughs off and is expelled through the vagina, but rather the uterine lining of rodents is reabsorbed during an estrous cycle.²⁴ The rat estrous cycle is typically 4 to 5 d in length and is defined by 4 separate stages: proestrus, estrus, metestrus, and diestrus. Proestrus is characterized by increasing levels of estrogen. At the end of proestrus, ovulation (signaled by luteinizing hormone) occurs and marks the beginning of the estrus cycle. During metestrus and diestrus, the uterine lining regenerates, and the cycle starts again.^24,33 These stages induce changes in the composition of the epithelium of the vagina and the presence of inflammatory cells, which can easily be detected by using vaginal cytology.^18,35We conducted the current study to determine whether estrous cycle stage influences the susceptibility to ischemia–reperfusion injury in the rat heart. Because the stage of the estrous cycle may influence cardiac injury either directly (via a direct effect of circulating hormones), or indirectly (by inducing changes that are intrinsic to the heart), we used both in vivo and ex vivo models of injury.     

Impact of 900 MHz electromagnetic field exposure on main male reproductive hormone levels: a Rattus norvegicus model

This work analyzes the effects of radiofrequency-electromagnetic field (RF-EMF) exposure on the reproductive system of male rats, assessed by measuring circulating levels of FSH, LH, inhibin B, activin B, prolactin, and testosterone. Twenty adult male Sprague–Dawley rats (180?±?10 g) were exposed to 900 MHz RF-EMF in four equal separated groups. The duration of exposure was 1, 2, and 4 h/day over a period of 30 days and sham-exposed animals were kept under the same environmental conditions as the exposed group except with no RF-EMF exposure. Before the exposure, at 15 and 30 days of exposure, determination of the abovementioned hormone levels was performed using ELISA. At the end of the experiment, FSH and LH values of the long time exposure (LTE) group were significantly higher than the sham-exposed group (p?p?p?相似文献   

Mus和Rattus属鼠类下颌骨形态特征测量分析系统建立

目的建立高精度低误差的《Mus和Rattus属鼠类下颌骨形态特征测量分析系统》。方法运用Microsoft Visual Basic6．0语言设计程序,自动测量、计算、分析下颌骨形态特征。实例运行评估其可操作性。结果本系统可提高测量精度28倍,减少计算误差40余倍。可适用于Mus和Rattus属的野生动物、实验动物的下颌骨形态特征测量分析。结论《Mm和Rottus属鼠类下颌骨形态特征测量分析系统》具有成为可操作的遗传检测方法。     

iTRAQ-coupled 2D LC–MS/MS analysis on differentially expressed proteins in denervated tibialis anterior muscle of Rattus norvegicus

To understand the molecular aspects of denervation-induced atrophy of skeletal muscles, isobaric tags for relative and absolute quantitation (iTRAQ) coupled with two-dimensional liquid chromatography-tandem mass spectrometry were performed to detect a total of 260 proteins that were differentially expressed in the rat tibialis anterior muscle at different times (1, 4, and 8 weeks) after rat sciatic nerve transection. Western blot, gene ontology, and Kyoto Encyclopedia of Genes and Genomes analyses were further conducted for protein validation, functional annotation, and pathway identification, respectively. Among 260 dysregulated proteins, metabolic enzymes represented the largest class of proteins differentially expressed; a down-regulation of β-enolase might be associated with a decreased expression of fast-twitch myosin-4; the 14-3-3 proteins displayed an up-regulation, which might facilitate the inhibition of mTOR signaling; an up-regulation of α-crystallin B chain might be related to the later onset and the slower progress of atrophy; an up-regulation of phosphatidylethanolamine-binding protein-1 perhaps progressively abrogated the cell survival and antiapoptotic properties during muscle atrophy. These results might contribute to the understanding of molecular mechanisms regulating denervation-induced muscle atrophy.     

How many species of Apodemus and Rattus occur in China? A survey based on mitochondrial cyt b and morphological analyses

Apodemus(mice) and Rattus(rats) are the top rodent reservoirs for zoonoses in China, yet little is known about their diversity. We reexamined the alpha diversity of these two genera based on a new collection of specimens from China and their cyt b sequences in Gen Bank. We also tested whether species could be identified using external and craniodental measurements exclusively. Measurements from 147 specimens of Apodemus and 233 specimens of Rattus were used for morphological comparisons. We analysed 74 cyt b sequences of Apodemus and 100 cyt b sequences of Rattus to facilitate phylogenetic estimations. Results demonstrated that nine species of Apodemus and seven species of Rattus, plus a new subspecies of Rattus nitidus, are distributed in China. Principal component analysis using external and craniodental measurements revealed that measurements alone could not separate the recognized species. The occurrence of Rattus pyctoris in China remains uncertain.     

Invasion by Rattus rattus into native coastal forests of south‐eastern Australia: are native small mammals at risk?

The black rat, Rattus rattus, is an alien rodent in Australian ecosystems where niche overlap with native small mammals may lead to competition for resources and displacement of native species. In coastal habitats surrounding Jervis Bay in south‐eastern Australia, R. rattus co‐occurs with the native bush rat, Rattus fuscipes, and brown antechinus, Antechinus stuartii. Relative distributions and abundances, and fine‐scale space use suggest invasive and native rodents compete for use of space and habitat. Such competitive interactions were not evident between R. rattus and native A. stuartii, which was negatively influenced more by disturbance to habitat. Differences in rodent communities between spatially separate forests forming the northern and southern peninsulas of Jervis Bay potentially reflect symmetrical competition and differences in competitive outcomes. In southern forests, R. rattus was largely restricted to patches of disturbed forest associated with campgrounds. Competitive interference by native rodent populations inhabiting surrounding intact forests may have so far limited R. rattus colonization of these areas. In northern forests, R. rattus was the predominant rodent irrespective of disturbance, while populations of R. fuscipes were unusually low seemingly due to poor juvenile recruitment. Native individuals avoided areas frequented by adult R. rattus and given that species did not partition use of microhabitats, R. rattus most likely precluded R. fuscipes from suitable habitat and in doing so limited native populations. We discuss how natural disturbance of habitat and human activity have potentially facilitated successful invasion by R. rattus of the northern forests. Studies that manipulate rodent populations are required to support these interpretations of observed patterns.     

珠江三角洲黄毛鼠(Rattus rattoides exiguus)天敌食性的初步观察

农田鼠害生物防治的可行性是人们非常关心的问题,也是鼠害综合防治的一个重要环节。本文着重从食性入手,观察研究了珠江三角洲黄毛鼠天敌滑鼠蛇的食性,以及其摄食量与温度、湿度的关系;并且还对黄毛鼠的另一类天敌(号鸟)类的食量情况作了初步观察。提出了对天敌在黄毛鼠生物防治的作用应采取一分为二的态度,一方面不宜过高估计其灭鼠作用,另一方面也应禁止捕捉鼠类天敌,保护其生活环境,维持生态平衡。     

Ontogenetic and sexual patterns in the cranial system of the brown rat (Rattus norvegicus Berkenhout, 1769) from Hai’l region,Kingdom of Saudi Arabia

The brown rat, Rattus norvegicus, is a model system in ecological and systematic science, but little is known about its skull morphology and developmental patterns. Our objective was to investigate the cranial ontogenetic patterns in the brown rats, from Hai’l, Kingdom of Saudi Arabia.Quantitative analysis of sexual shape dimorphisms (SShD) and age-classes were investigated using 28 landmarks plotted on two-dimensional images for dorsal and ventral views. Our results detected statistically significant sexual dimorphism (P-value <0.0001) in cranial shape and size for R. norvegicus. Nevertheless, males are much larger than females and display variation around the brain-case, while females tend to show greater variation around the occipital bone. In addition, there are subtle age-classes during ontogeny in the skull. However, the older age classes (i.e. age classes 3 and 4) represent well-built crania with an extended case of the brain and shortest nasal, while youngest specimens represent an elongated snout of minimum crania.Future GMM research should therefore examine the pre-defined age-classes and sex-related individuals in brown rat skulls in relation to genotype to characterize trends in skull shape variation that may affect teeth, zygomatic arches, brain case, and compartments of muscle attachments through its ecological patterns.     

大鼠(Rattus norvegicus)微量血培养和染色体标本制作的方法

本文介绍了大鼠微量血培养和制备染色体标本的简易方法。通过多次反复实验,确证了这个培养方法是有效的和可采用的。在结果讨论中,还比较分析了各种因素(包括培养时间、PHA剂量、pH值和肝素剂量)对细胞生长分裂的影响。同时初步确定了大鼠淋巴细胞分裂周期为16小时左右。     

Do rats mind getting their feet dirty? Observing the behaviour of ship rats (Rattus rattus) towards footprint tracking tunnels

Monitoring rat populations by standard tracking tunnels assumes that rats do not avoid treading on the tracking ink. We observed the behaviour of 20 rats in four groups of five, spending 2 nights each (40 trials) in large observation pens. In only 10 of 40 trials did the rat run through a tunnel without hesitation on first encounter, while in four trials a rat approached the tunnel up to 35 times but refused to run though it all night. Most rats approached and turned away between two and 34 times before running through. Observations through transparent tunnels of rats pausing for a mean of 3.2 s before stepping on the ink suggest that they probably could detect it, but they usually chose to ignore it. Experience of encountering the ink pad inside a black tunnel did not deter rats from running across another one, and would not affect indices of rat abundance reaching levels high enough to trigger conservation concern, but variation in behavioural reactions to tracking tunnels could possibly affect the detection rate of rats at low density.     

Response of mice (Mus musculus) to the removal of black rats (Rattus rattus) in arid forest on Santa Cruz Island, Galápagos

A combined rat and mouse trapping grid was established in arid coastal forest on Santa Cruz Island, Galápagos over June and July 2009. Mouse traps were opened first and did not initially catch any mice. Rat traps were opened four days later and began catching rats on the second night. Mice were trapped in increasing numbers only after the rat catch-rate had declined substantially. Interference with bait at rat traps also increased. The estimated density of rats was 4.8 rats/ha and mice 32.3/ha. The results suggest mice were present but their activity and/or numbers were being suppressed by the larger rodent. This conclusion has implications for competitive exclusion of native Galápagos rodents by both introduced species. It also suggests caution for rodent abundance estimates and planned rodent eradications when two or more species are present.