Species Mus Research Articles

Musin Morocco: a Quaternary sequence of intraspecific evolution

North Africa is an intricate biogeographical region at the crossroads of immigration waves from tropical Africa and Asia. Species confined between various barriers (Atlas Mountains, arid environments such as the Sahara in the south, water masses such as the Mediterranean Sea in the north, and the Atlantic Ocean in the west) were generally forced to adapt locally to environmental changes instead of tracking their habitat by shifting their distribution area. The present study aims at providing first insight into the evolution of the genus Mus, and more specifically of the western Mediterranean species Mus spretus in this area. The study relies on the abundant Late Pleistocene and Middle Holocene fossil assemblage from the El Harhoura 2 cave (Rabat-Temara, Morocco). This exceptional record was studied using geometric morphometrics applied to first upper and lower molars, constituting the most informative and best preserved fossil remains for such small rodents. Two main issues were addressed. (1) Geometric morphometrics was used to clarify taxonomic status and phylogenetic relationships among fossil and modern species in this area. Morphometric analysis revealed good discrimination of most modern and fossil species but failed to document intermediate forms tracing anagenetic evolution. Not mutually exclusive, the occurrence of complex processes of morphological evolution in this genus such as parallel evolution and the action of stabilizing selection may make it difficult to translate patterns of morphological evolution into phylogenetic conclusions. (2) The record was shown to document a sequence of intraspecific evolution of M. spretus. The morphology of the molars through the fossil record of El Harhoura 2 was surprisingly stable despite extensive modern variation. The limited temporal variation largely failed to correlate to palaeoenvironmental proxies. The mouse fossil record at El Harhoura 2 thus presents an intriguing case of morphological stasis despite extensive environmental changes. This long-term stability may have been recently perturbed by anthropogenic factors including landscape changes and introduction of various competitors and predators, leading to a size reduction. © 2013 The Linnean Society of London, Biological Journal of the Linnean Society, 2013, 109, 599–621.

Acute toxicity evaluation of Genipa americana L. (Rubiaceae)

</I>;The specie G. americana L. (Rubiaceae) is an exotic plant with edible fruit, aphrodisiac, antianaemic and useful in diseases of the spleen and liver. The objective of this study was to determine the acute toxicity of crude ethanol extract of the fruit of G. americana parameters by evaluating general toxicity. For the tests were selected Swiss albino mice of the species Mus musculus females, weighing 25–30g were divided into groups of six. The animals were kept in polypropylene cages under controlled lighting (cycle 12 hours light/dark) and temperature (25 ± 2 °C), receiving food and water ad libtum. The doses of 1000, 2000 and 3000 mg/kg administered intraperitoneally (VIP) and 1500, 3000 and 4500 mg/kg orally. The 50% lethal dose (LD50) was not determined due to lack of deaths of the animals at the doses employed, being regarded maximal for the route. Among the signs of toxicity observed highlight the stimulating effect on the CNS. The results indicate that the ethanol extract of G. americana has low acute toxicity in mice when administered by oral and intraperitoneal administration.

Antinociceptive, neurobehavioral and antioxidant effects of Eupatorium triplinerve Vahl on rats

Ethnopharmacological relevanceEupatorium triplinerve Vahl belongs to the Asteraceae family, popularly known as Japana. It is a perennial shrub native to Amazon rainforests of South America. Its leaves are used through infusions, decoctions, baths, and tea. It is largely used in Brazilian folk medicine as sedative, febrifuge, stimulant, tonic and anti-inflammatory. Aim of the studyThe present study evaluated the putative effects of Eupatorium triplinerve on the central nervous system (CNS), including locomotor and anxiety activity, depression-like behavior, and antinociception and oxidative stress. Materials and methodsTwo-month-old male Wistar rats (n=7–10 rats/group) and Swiss male and female mice of the species Mus musculus (n=7–10 per group) were administered with 100mg/kg, 200mg/kg, 400mg/kg, 600mg/kg, and 800mg/kg of hydroalcoholic extracts of Eupatorium triplinerve (HEET). The behavioral assays included open-field (OF), elevated Plus-maze (EPM), and forced swimming tests (FS). The antinociceptive activity was verified using chemical (acetic acid and formalin) and thermal (hot plate) models of nociception. The oxidative stress levels were measured in rat blood samples after behavioral assays and Trolox equivalent antioxidant capacity (TEAC), nitric oxide and malondialdehyde (MDA) levels were measured in vivo. ResultsOral pretreatment with HEET reduced the locomotion in OF test (200–800mg/kg), increased central locomotion and open arms entries in the OF and EPM tests, respectively (600–800mg/kg), and decreased the immobility time in the FS (200–800mg/kg). It also reduced the writhing number evoked by acetic acid injection (200–800mg/kg) and licking time in the first phase of the formalin test (400–800mg/kg). In the oxidative stress assays, the extract decreased TEAC, Nitric Oxide and MDA levels in response to swimming stress induced in rats. ConclusionsThese results were indicative for the first time that Eupatorium triplinerve exerted mild sedative, anxiolytic and antidepressive effects on the CNS. Antinociceptive effects not related to opioid system and antioxidant activity were also observed. These results support the ethnopharmacological use of Eupatorium triplinerve in popular medicine.

Comparing Habitat Type and Abundance within the Urra Small Mammal Population

This study set out to explore two objectives. Firstly the abundance of small mammals in two varying habitats (a well vegetated orchard terrace and a sparsely vegetated dry riverbed) in Southern Spain; and secondly to compare the efficiency of the two traps used (Longworth and Sherman). Traps were equally spaced apart in the 40 m 2 trapping areas using a grid pattern. The two trap types were arranged alternately and checked four times a day (twice during darkness hours and twice during daylight hours). Our two main hypotheses associated with our objectives were proven to be correct as significantly more small mammals were captured in the orchard terrace than in the dry river bed (P<0.001; df =1) and Longworth traps were by far the most superior over the Sherman traps (with a success rate 48 more times greater than the later). Our findings show that the dominant species Mus spretus prefers areas of more continuous habitat rather than the sparsely vegetated dry riverbed and that the longworth traps were best suited to capturing the size of mammals that this study found. This study will help to act as a recommendation to further long term research of population sizes in similar habitats.

Natal dispersal in two mice species with contrasting social systems

We compared the natal dispersal behaviour of two mice species under laboratory conditions. Natal dispersal is a movement of an animal from its birthplace to its breeding area. This behaviour is known to be influenced by the mating system. In polygamous species, males are more likely to disperse, while in most of the monogamous spe- cies, both sexes disperse. Our subjects, the house mouse (Mus musculus) and the mound-building mouse (Mus spic- ilegus) are two sympatric species of the genus Mus. Both are native in Hungary, but they differ in their habitat type mating system and overwintering strategy. The house mouse is a polygynous species and adapted to human environment, known for mature and reproduce early. On the contrary, the mound-building mice are monogamous, and they inhabit extensively used agricultural fields, where they spend the unfavourable winter period in nest chambers under mounds, which they construct from soil and plant material. Success- ful overwintering for this species demands delayed maturity and reduced dispersion during the winter. Our results showed that the natal dispersal of these two species differ; both sexes of the mound-building mice dispersed later than the house mice, where a difference between sexes also occurs; house mice males dispersed earlier than females. The mound-building mice showed no sexual dimorphism in this behaviour.

Verification of natural infection of peridomestic rodents by PCV2 on commercial swine farms

The porcine circovirus-2 (PCV2) is the main agent responsible for porcine circovirus associated diseases (PCVAD). Few studies have been done regarding PCV2 infection in other species. The purpose of this study was to investigate the occurrence of PCV2 infection in the peridomestic rodent species Mus musculus and Rattus rattus on commercial pig farms in Brazil. Immunohistochemistry assay demonstrated PCV2 in the spleen, lung and kidney. Viral DNA was detected in tissues by nested PCR assay. Partial sequences of PCV2 genomes detected in the rodents had strong identity with gene sequences of PCV2 isolates from pigs. These results show that the studied peridomestic rodent species can be naturally infected by PCV2. However, further studies are needed to confirm PCV2 transmission from rodents to pigs.

Genomic variation in the vomeronasal receptor gene repertoires of inbred mice.

BackgroundVomeronasal receptors (VRs), expressed in sensory neurons of the vomeronasal organ, are thought to bind pheromones and mediate innate behaviours. The mouse reference genome has over 360 functional VRs arranged in highly homologous clusters, but the vast majority are of unknown function. Differences in these receptors within and between closely related species of mice are likely to underpin a range of behavioural responses. To investigate these differences, we interrogated the VR gene repertoire from 17 inbred strains of mice using massively parallel sequencing.ResultsApproximately half of the 6222 VR genes that we investigated could be successfully resolved, and those that were unambiguously mapped resulted in an extremely accurate dataset. Collectively VRs have over twice the coding sequence variation of the genome average; but we identify striking non-random distribution of these variants within and between genes, clusters, clades and functional classes of VRs. We show that functional VR gene repertoires differ considerably between different Mus subspecies and species, suggesting these receptors may play a role in mediating behavioural adaptations. Finally, we provide evidence that widely-used, highly inbred laboratory-derived strains have a greatly reduced, but not entirely redundant capacity for differential pheromone-mediated behaviours.ConclusionsTogether our results suggest that the unusually variable VR repertoires of mice have a significant role in encoding differences in olfactory-mediated responses and behaviours. Our dataset has expanded over nine fold the known number of mouse VR alleles, and will enable mechanistic analyses into the genetics of innate behavioural differences in mice.

Protection Against Toxoplasmosis in Swiss Albino Mice Immunized with Attenuated Toxoplasma Gondi

The present study aimed at investigation on developing the immune response against Toxoplasmosis in Swiss Albino mice of the species Mus musculus, BALB/c strain, which were infected, experimentally, with Toxoplasma gondii in order to render the host able to resist any infection with this disease in the future. To achieve this, Toxoplasma gondii tissue cysts, collected from placenta of aborted women, they attenuated by irradiation with two absorbed doses of X-Ray irradiation 0.4 and 0.8 KGy. Mice were injected, intraperitoneally with tissue cysts at a rate of 100 cysts/mice single or double doses. In addition, groups of mice were injected with non-irradiated tissue cysts, as a positive control groups. The criteria used in the present study was humoral immunity, represented by IgM using Enzyme-Linked Immunosorbent Assay (ELISA IgM) to demonstrate the differentiated in IgM level between mice inoculated with X-Ray irradiated tissue cysts and positive control groups, which infected with non- irradiated tissue cysts. The result shown that the immunization with X-Ray irradiated Toxoplasma gondii tissue cysts could partially protect the mice from Toxoplasma gondii infection, and produce specific IgM antibody.

Therapeutic vaccination with Salmonella-delivered codon-optimized outer inflammatory protein DNA vaccine enhances protection in Helicobacter pylori infected mice

Vaccination had demonstrated as an alternative way to combat Helicobacter pylori challenge. In the present study, codon-optimized outer inflammatory protein gene (oipA) for Mus species codon usage, the inclusion of optimal Kozak sequence, and modified of GC content was applied to construct a novel DNA construct. The Salmonella-delivered wild type oipA construct (SL7207/poipA) and the Salmonella-delivered codon-optimized oipA construct (SL7207/poipA-opt) were prepared and their therapeutic efficacy was evaluated in H. pylori-infected mice. The codon-optimized oipA construct (poipA-opt) expressed almost six-fold higher protein than that of wild type construct (poipA) as normalized to the β-actin expression in AGS cells. Oral therapeutic immunization with SL7207/poipA-opt significantly eliminated H. pylori colonization in the stomach; and protection was related to a robust Th1/Th2 immune response. Therefore, our results suggested that fine therapeutic efficacy was related to sufficient expression of the antigen. It is supposed that codon-optimized oipA gene improves protein expression and consequently enhances the immunogenicity of DNA vaccine, which resulted in a significant reduction of bacterial loads in H. pylori infected mice. The Salmonella-delivered codon-optimized DNA construct could be a candidate vaccine against H. pylori for the clinical application.

Nasal bone shape is under complex epistatic genetic control in mouse interspecific recombinant congenic strains.

BackgroundGenetic determinism of cranial morphology in the mouse is still largely unknown, despite the localization of putative QTLs and the identification of genes associated with Mendelian skull malformations. To approach the dissection of this multigenic control, we have used a set of interspecific recombinant congenic strains (IRCS) produced between C57BL/6 and mice of the distant species Mus spretus (SEG/Pas). Each strain has inherited 1.3% of its genome from SEG/Pas under the form of few, small-sized, chromosomal segments.ResultsThe shape of the nasal bone was studied using outline analysis combined with Fourier descriptors, and differential features were identified between IRCS BcG-66H and C57BL/6. An F2 cross between BcG-66H and C57BL/6 revealed that, out of the three SEG/Pas-derived chromosomal regions present in BcG-66H, two were involved. Segments on chromosomes 1 (∼32 Mb) and 18 (∼13 Mb) showed additive effect on nasal bone shape. The three chromosomal regions present in BcG-66H were isolated in congenic strains to study their individual effect. Epistatic interactions were assessed in bicongenic strains.ConclusionsOur results show that, besides a strong individual effect, the QTL on chromosome 1 interacts with genes on chromosomes 13 and 18. This study demonstrates that nasal bone shape is under complex genetic control but can be efficiently dissected in the mouse using appropriate genetic tools and shape descriptors.

The micromammals of Minoan Crete: human intervention in the ecosystem of the island

The present paper deals with small mammal cranial and postcranial remains from two Bronze Age archaeological sites on Crete, Greece: Mochlos on Eastern Crete and Khania on Western Crete. The endemic Pleistocene species Mus minotaurus and Crocidura zimmermanni were identified in skeletal material from archaeological excavations under the modern city of Khania, while M. musculus domesticus and C. cf. suaveolens were identified in skeletal material from archaeological excavations in the Minoan town of Mochlos. Other identified species include Suncus etruscus and Apodemus sylvaticus/flavicollis. Issues of island biodiversity changes between Pleistocene and Holocene as well as the dates of appearance of the various large and small mammals on Crete are discussed. New dates for the introduction of new micromammal species by modern humans are proposed. The non-endemic species, C. cf. suaveolens, and especially the house mouse, M. musculus domesticus, indicate accidental introduction by humans from the eastern Mediterranean and competition with the endemic ones that led to extinction of M. minotaurus and a radical change of the micromammal zoogeography of Crete.

Differential expression of the Gstp2 gene between the aboriginal species Mus spretus and the laboratory mouse Mus musculus

Glutathione S-transferases (GSTs) are pivotal phase-II enzymes for detoxification of xenobiotics. Pi-class GSTs play key roles in determining cancer susceptibility. The laboratory mouse Mus musculus (Mm) has two GST-Pi-encoding genes; while MmGstp1 is the counterpart of the unique human and rat Pi-class GST gene, the function of MmGstp2 remains unclear because its expression is almost undetectable in liver and its product lacks activity against typical GST/GST-Pi substrates. Mus spretus (Ms) is an aboriginal mouse species of great interest as a bio-indicator in environmental pollution studies and a reservoir of novel allelic variants and phenotypes. Using absolute real-time RT-PCR, we demonstrate significant differences in the hepatic levels of GST-Pi-encoding mRNAs between both mouse species. Particularly, we found that the Gstp2 gene of M. spretus, unlike its M. musculus counterpart, attains relatively high steady-state level of expression (∼30molecules/pg of total liver RNA in mice dwelling in a non-polluted area). To test whether the interspecies difference in Gstp2 mRNA levels is due, at least in part, to evolutionary divergence in the promoter regions, we (i) sequenced the 5′-flanking regulatory regions of the two Gstp2 genes; (ii) used bioinformatics tools to identify differences in TF binding sites (TFBSs) and cis-regulatory modules; and (iii) extended the in silico results to a cell-based functional assay. We observed high sequence divergence (2.8%) and differences in TFBSs (32.6%) between the two Gstp2 promoters. We also show that constructs harbouring promoter fragments with species-specific cis-regulatory motifs displayed differential luciferase reporter activity, suggesting that these promoter sequence variations may determine, at least in part, the strong difference in Gstp2 mRNA levels between M. musculus and M. spretus. Additionally, the comparative analysis of the coding sequences predicts that the MsGstp2 product may be an active Pi-class GST because of a Pro12 to Arg12 substitution. Interestingly, free-living M. spretus mice dwelling at an industrial settlement displayed significantly higher amounts of transcripts for both GST-P1 and GST-P2 than those from a non-polluted area, suggesting that. M. spretus may optimise the response to pollution by co-evolving the expression levels of the two Pi-class GST genes. Overall, our data suggest that MsGstp2 may be one of the genes contributing to the natural resistance of M. spretus, facilitating its adaptation in a wild environment. Further insights into the functional roles of mouse Pi-class GSTs should be gained from the data reported in this work.

Host cell/Orientia tsutsugamushi interactions: Evolution and expression of syndecan-4 in Asian rodents (Rodentia, Muridae)

Scrub typhus is an acute febrile zoonotic disease and worldwide more than a billion people may be at risk for infection. Orientia tsutsugamushi, the causative agent of scrub typhus, is an obligate intracellular bacterium. Rodents are reported to be the primary reservoir hosts of the disease and according to the most recent surveys, all species within the Rattus sensu lato complex of the tribe Rattini are carriers of scrub typhus. There is no evidence that any of mouse (Mus) species serves as the primary reservoir of the bacterium even when occurring in sympatry with wild infected rats. This contrast in the host/syndecan-4 interactions between Rattini and Asian Murini may be due to intrinsic (i.e., genetic) differences. Herein we compare the sequence and expression levels of syndecan-4 (the putative cell receptor of O. tsutsugamushi) between Rattini species that are known to be natural reservoirs for the typhus agents, and Murini species that are not. Although it was not possible to conclusively link the structural variations detected in syndecan-4 with carrier status in either Rattini and Murini, our findings indicate the absence of a strong Orientia-mediated selective regime acting on gene structure. In contrast, variable spleen-specific syndecan-4 expression levels show a strong correlation between under-expression of syndecan-4 in Murini and seropositive Rattini, compared to seronegative Rattini rodents. We postulate that two divergent responses may be at work in Murini and Rattini, both linked with differential expression of syndecan-4: (i) reduced syndecan-4 transcription in Murini decreases the likelihood that the host cells will become infected by the Orientia bacterium, while (ii) reduced syndecan-4 expression in seropositive Rattini limits the pathogenicity of Orientia and consequently improves the longevity of the rat hosts. These patterns may underpin the poor carrier status of wild mice on the one hand, and the effective role of wild rats as reservoir hosts on the other.

Two Genetic Determinants Acquired Late in Mus Evolution Regulate the Inclusion of Exon 5, which Alters Mouse APOBEC3 Translation Efficiency

Mouse apolipoprotein B mRNA-editing enzyme catalytic polypeptide-like editing complex 3 (mA3), an intracellular antiviral factor, has 2 allelic variations that are linked with different susceptibilities to beta- and gammaretrovirus infections among various mouse strains. In virus-resistant C57BL/6 (B6) mice, mA3 transcripts are more abundant than those in susceptible BALB/c mice both in the spleen and bone marrow. These strains of mice also express mA3 transcripts with different splicing patterns: B6 mice preferentially express exon 5-deficient (Δ5) mA3 mRNA, while BALB/c mice produce exon 5-containing full-length mA3 mRNA as the major transcript. Although the protein product of the Δ5 mRNA exerts stronger antiretroviral activities than the full-length protein, how exon 5 affects mA3 antiviral activity, as well as the genetic mechanisms regulating exon 5 inclusion into the mA3 transcripts, remains largely uncharacterized. Here we show that mA3 exon 5 is indeed a functional element that influences protein synthesis at a post-transcriptional level. We further employed in vitro splicing assays using genomic DNA clones to identify two critical polymorphisms affecting the inclusion of exon 5 into mA3 transcripts: the number of TCCT repeats upstream of exon 5 and the single nucleotide polymorphism within exon 5 located 12 bases upstream of the exon 5/intron 5 boundary. Distribution of the above polymorphisms among different Mus species indicates that the inclusion of exon 5 into mA3 mRNA is a relatively recent event in the evolution of mice. The widespread geographic distribution of this exon 5-including genetic variant suggests that in some Mus populations the cost of maintaining an effective but mutagenic enzyme may outweigh its antiviral function.

Discovery of novel variants in genotyping arrays improves genotype retention and reduces ascertainment bias.

BackgroundHigh-density genotyping arrays that measure hybridization of genomic DNA fragments to allele-specific oligonucleotide probes are widely used to genotype single nucleotide polymorphisms (SNPs) in genetic studies, including human genome-wide association studies. Hybridization intensities are converted to genotype calls by clustering algorithms that assign each sample to a genotype class at each SNP. Data for SNP probes that do not conform to the expected pattern of clustering are often discarded, contributing to ascertainment bias and resulting in lost information - as much as 50% in a recent genome-wide association study in dogs.ResultsWe identified atypical patterns of hybridization intensities that were highly reproducible and demonstrated that these patterns represent genetic variants that were not accounted for in the design of the array platform. We characterized variable intensity oligonucleotide (VINO) probes that display such patterns and are found in all hybridization-based genotyping platforms, including those developed for human, dog, cattle, and mouse. When recognized and properly interpreted, VINOs recovered a substantial fraction of discarded probes and counteracted SNP ascertainment bias. We developed software (MouseDivGeno) that identifies VINOs and improves the accuracy of genotype calling. MouseDivGeno produced highly concordant genotype calls when compared with other methods but it uniquely identified more than 786000 VINOs in 351 mouse samples. We used whole-genome sequence from 14 mouse strains to confirm the presence of novel variants explaining 28000 VINOs in those strains. We also identified VINOs in human HapMap 3 samples, many of which were specific to an African population. Incorporating VINOs in phylogenetic analyses substantially improved the accuracy of a Mus species tree and local haplotype assignment in laboratory mouse strains.ConclusionThe problems of ascertainment bias and missing information due to genotyping errors are widely recognized as limiting factors in genetic studies. We have conducted the first formal analysis of the effect of novel variants on genotyping arrays, and we have shown that these variants account for a large portion of miscalled and uncalled genotypes. Genetic studies will benefit from substantial improvements in the accuracy of their results by incorporating VINOs in their analyses.

A comparative study of the diets of barn owl (Tyto alba) and spotted owlet (Athene brama) inhabiting Ahmadpur East, Southern Punjab, Pakistan

AbstractThe diets of the barn owl (Tyto alba) and the spotted owlet (Athene brama) inhabiting the periphery of the Cholistan Desert at Ahmedpur East, southern Punjab were compared. Pellets of the two owl species were analyzed to learn more about their diets. The barn owl mainly consumed Suncus murinus (60.2%), birds (24.1%) and rodents (12.7%), while the spotted owlet depended on Mus species (36.8%), Suncus murinus (20.1%), birds (14.1%), reptiles (8.9%) and insects (6.7%) for its food. There was a low degree of food overlap of the two owls among the seasons.

Ecological Aspects of Rodent Communities in Agrarian Ecosystems of Moldova

The transformations of anthropogenic ecosystems in the last decades provoked significant structural-functional changes in rodent communities, as well as modification of dominance status of some wide spread species. In the 80s the dominant species were those from genus Apodemus, with 63%, of which A. sylvaticus and A. uralensis had the abundance of 55%, being constant on the agricultural fields. The genus Mus species had the abundance of 25% and were the main species on agricultural fields. M. musculus was more frequent and more abundant (15%). After 2000 the abundance of some rodent species increased (A. agrarius, M. spicilegus) and of other species decreased (A. sylvaticus, A. uralensis M. musculus). In the last years abundance decreasing of M. spicilegus was registered. The Microtus vole population is in depression phase its abundance decreasing from about 20% in 2006 to 3% in 2009 and is still low. A. sylvaticus is the most prosperous species among rodents, being dominant and constant in the republic ecosystems.

Mouse "xenotropic" gammaretroviruses, XMRV and their XPR1 receptor

Background Xenotropic/polytropic mouse leukemia viruses (XPMLVs) and the xenotropic murine leukemia virusrelated virus (XMRV) identified in human patient samples rely on the XPR1 receptor for entry into cells. There are 5 functional variants of Xpr1 in Mus species and laboratory mouse strains that differ in their ability to support entry of XMRV and various isolates of XPMLVs. Additional receptor variants are found in nonrodent vertebrate species.

Differences in hippocampal protein levels between C57Bl/6J, PWD/PhJ, and Apodemus sylvaticus are paralleled by differences in spatial memory

There is a significant strain-dependent performance in the Morris water maze (MWM), a paradigm for the evaluation of spatial memory. In contrast, information on molecular differences that may be responsible for differences in spatial memory performance is limited. The aim of the study was therefore to investigate differences in hippocampal protein levels in three groups with different performance in the MWM. C57BL/6J (inbred laboratory strain), PWD/PhJ (inbred strain derived from wild animals of Mus musculus), and Apodemus sylvaticus (AS, genus Apodemus) mice were used for the experiments. Proteins from hippocampi, obtained from a behavioral study on these animals, were extracted and run on two-dimensional gel electrophoresis. Proteins spots were quantified, and spots with significantly different levels were identified by mass spectrometry using an ion trap. A series of 49 proteins from different pathways and cascades (signaling, neuronal network, protein synthesis, secretion and degradation, and antioxidant system; intermediary, fat, and carbohydrate metabolism) were significantly different among hippocampi at the stringent statistical level of P ≤ 0.001. These findings are paralleled by differences in the spatial navigation abilities between the strains within the species Mus musculus (C57BL/6 vs. PWD/PhJ) and between the genera Mus and Apodemus. As shown previously, AS learned the task in the MWM and showed good memory retention when tested at the probe trial (day 12), whereas C57BL/6J learned the task, but failed at the probe trial at day 12 as well as PWD/PhJ that failed to learn the task and failed at the probe trial at day 12. A list of above-mentioned proteins were different between PWD/PhJ with bad and AS with good memory retention and may therefore be related to performance in the MWM and thus to spatial memory formation. The experimental approach, however, does not allow discriminating between differences in protein levels a priori and different protein levels induced by the MWM testing. © 2010 Wiley-Liss, Inc.

Reproductive Rates in Australian Rodents Are Related to Phylogeny

BackgroundThe native rodents of Australia are commonly divided into two groups based on the time of their colonization of the Sahulian continent, which encompasses Australia, New Guinea, and the adjacent islands. The first group, the “old endemics,” is a diverse assemblage of 34 genera that are descended from a single colonization of the continent during the Pliocene. A second group, the “new endemics,” is composed of several native Rattus species that are descended from a single colonization during the Pleistocene. Finally, a third group is composed of three non-native species of Rattus and Mus introduced into Australia by humans over the last 200 years. Previous studies have claimed that the three groups differ in their reproductive rates and that this variation in rates is associated with the unique environmental conditions across Australia. We examined these hypotheses using phylogenetically controlled methods.Methodology and ResultsWe examined the relationship between the reproductive rates of the Australian rodents and the environmental variations across the continent, as well as the epoch of their colonization of the continent. Our results revealed no significant correlation with environmental variables but a significant association between colonization age and all the reproductive parameters examined.DiscussionBased on a larger phylogeny of the subfamily Murinae, we showed that significant differences in reproductive rates among colonization groups are shared with their closest relatives outside Sahul. Therefore, the lower reproductive rates in the old endemics are more likely to be the result of phylogenetic history and conservation of traits than an adaptation to the Australian environment. In the new endemics, we found a trend of increasing reproductive rates with diversification. We suggest that the differences in reproductive rates of the old endemic rodents and the native Rattus represent alternative adaptive strategies that have allowed them to utilize similar ecological niches across Australia.