Large nesting expression in deer mice remains stable under conditions of visual deprivation despite heightened limbic involvement: Perspectives on compulsive-like behavior.

Visual stimuli and limbic activation varyingly influence obsessive-compulsive symptom expression and so impact treatment outcomes. Some symptom phenotypes, for example, covert repugnant thoughts, are likely less sensitive to sensory stimuli compared to symptoms with an extrinsic focus, that is, symptoms related to contamination, safety, and "just-right-perceptions." Toward an improved understanding of the neurocognitive underpinnings of obsessive-compulsive psychobiology, work in naturalistic animal model systems is useful. Here, we explored the impact of visual feedback and limbic processes on 24 normal (NNB) and large (LNB) nesting deer mice, respectively (as far as possible, equally distributed between sexes). Briefly, after behavioral classification into either the NNB or LNB cohorts, mice of each cohort were separated into two groups each and assessed for nesting expression under either standard light conditions or conditions of complete visual deprivation (VD). Nesting outcomes were assessed in terms of size and neatness. After nesting assessment completion, mice were euthanized, and samples of frontal-cortical and hippocampal tissues were collected to determine serotonin and noradrenaline concentrations. Our results show that LNB, as opposed to NNB, represents an inflexible and excessive behavioral phenotype that is not dependent on visually guided action-outcome processing, and that it associates with increased frontal-cortical and hippocampal noradrenaline concentrations, irrespective of lighting condition. Collectively, the current results are informing of the neurocognitive underpinnings of nesting behavior. It also provides a valuable foundation for continued investigations into the noradrenergic mechanisms that may influence the development and promulgation of excessive, rigid, and inflexible behaviors.

Evolution of gene expression across brain regions in behaviourally divergent deer mice.

The evolution of innate behaviours is ultimately due to genetic variation likely acting in the nervous system. Gene regulation may be particularly important because it can evolve in a modular brain-region specific fashion through the concerted action of cis- and trans-regulatory changes. Here, to investigate transcriptional variation and its regulatory basis across the brain, we perform RNA sequencing (RNA-Seq) on ten brain subregions in two sister species of deer mice (Peromyscus maniculatus and P. polionotus)-which differ in a range of innate behaviours, including their social system-and their F1 hybrids. We find that most of the variation in gene expression distinguishes subregions, followed by species. Interspecific differential expression (DE) is pervasive (52-59% of expressed genes), whereas the number of DE genes between sexes is modest overall (~3%). Interestingly, the identity of DE genes varies considerably across brain regions. Much of this modularity is due to cis-regulatory divergence, and while 43% of genes were consistently assigned to the same gene regulatory class across subregions (e.g. conserved, cis- or trans-regulatory divergence), a similar number were assigned to two or more different gene regulatory classes. Together, these results highlight the modularity of gene expression differences and divergence in the brain, which may be key to explain how the evolution of brain gene expression can contribute to the astonishing diversity of animal behaviours.

Adult Offspring of Deer Mouse Breeding Pairs Selected for Normal and Compulsive-Like Large Nesting Expression Invariably Show the Same Behavior Without Prior In-Breeding.

Obsessive-compulsive disorder is a neuropsychiatric condition with notable genetic involvement. Against this background, laboratory-housed deer mice of both sexes varyingly present with excessive and persistent large nesting behavior (LNB), which has been validated for its resemblance of clinical compulsivity. Although LNB differs from normal nesting behavior (NNB) on both a biological and cognitive level, it is unknown to what extent the expression of LNB and NNB is related to familial background. Here, we randomly selected 14 NNB- and 14 LNB-expressing mice (equally distributed between sexes) to constitute 7 breeding pairs of each phenotype. Pairs were allowed to breed two successive generations of offspring, which were raised until adulthood (12 weeks) and assessed for nesting expression. Remarkably, our findings show that offspring from LNB-expressing pairs build significantly larger nests compared to offspring from NNB-expressing pairs and the nesting expression of the offspring of each breeding pair, irrespective of parental phenotype or litter, is family specific. Collectively, the results of this investigation indicate that LNB can be explored for its potential to shed light on heritable neurocognitive mechanisms that may underlie the expression of specific persistent behavioral phenotypes.

Experimental Infection of North American Deer Mice with Clade I and II Monkeypox Virus Isolates.

The global spread of monkeypox virus has raised concerns over the establishment of novel enzootic reservoirs in expanded geographic regions. We demonstrate that although deer mice are permissive to experimental infection with clade I and II monkeypox viruses, the infection is short-lived and has limited capability for active transmission.

Phylogeography within the Peromyscus maniculatus species group: Understanding past distribution of genetic diversity and areas of refugia in western North America.

The effects of anthropogenic climate change on biodiversity have been recognized on every continent, ocean, and across different taxonomic groups. Here, we study the range dynamics and demography of a cosmopolitan species: the deer mouse, Peromyscus maniculatus. We generated a multilocus SNP dataset using the ddRADseq protocol for 218 individuals across the geographic range within three western North American lineages of this species group. We evaluated population structure using several methods and explored the correlation between geographic and genetic distances. We modeled the demographic history using a site frequency spectrum approach and used a machine learning algorithm to infer current and past (Last Glacial Maximum; LGM) environmental suitability. Lastly, we explored the origin of population expansion for the identified lineages. The genome-wide SNP dataset was able to identify-three regionally distinct groups- 1) P. m. gambelii (southern California); 2) P. keeni (Pacific Northwest); 3) P. m. sonoriensis (a broad population spanning the Pacific Northwest through central California and across the Rocky Mountains into the Great Plains). Demographic analysis indicated the splits between the three populations occurred within the last 500 thousand years, with one very recent (late Holocene) split. Ecological niche models for each of these lineages predicted suitable environment present throughout their known ranges for current conditions, and a severe reduction of northern habitat in the past. The deer mouse has responded to past climate changes by expanding its range during interglacial periods and contracting its range during glacial periods leading to strong population differentiation. But lower magnitude climate change or other processes within the Holocene interglacial period led to population differentiation as well, which is likely still ongoing today given the substantial anthropogenic climate change and other landscape transformations caused by humans during the Anthropocene. By understanding the historical processes that led to the contemporary geographic distribution of biodiversity, we can determine the relative importance of different factors that shape biodiversity, now and into the future.

Peridomestic Mammal Susceptibility to Severe Acute Respiratory Syndrome Coronavirus 2 Infection.

Wild animals have been implicated as the origin of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), but it is largely unknown how the virus affects most wildlife species and if wildlife could ultimately serve as a reservoir for maintaining the virus outside the human population. We show that several common peridomestic species, including deer mice, bushy-tailed woodrats, and striped skunks, are susceptible to infection and can shed the virus in respiratory secretions. In contrast, we demonstrate that cottontail rabbits, fox squirrels, Wyoming ground squirrels, black-tailed prairie dogs, house mice, and racoons are not susceptible to SARS-CoV-2 infection. Our results expand the knowledge base of susceptible species and provide evidence that human-wildlife interactions could result in continued transmission of SARS-CoV-2.

Stereotypy and spontaneous alternation in deer mice and its response to anti-adenosinergic intervention.

Repetitive behavioral phenotypes are a trait of several neuropsychiatric disorders, including obsessive-compulsive disorder (OCD). Such behaviors are typified by complex interactions between cognitive and neurobiological processes which most likely contribute to the suboptimal treatment responses often observed. To this end, exploration of the adenosinergic system may be useful, since adenosine-receptor modulation has previously shown promise to restore control over voluntary behavior and improve cognition in patients presenting with motor repetition. Here, we employed the deer mouse (Peromyscus maniculatus bairdii) model of compulsive-like behavioral persistence, seeking to investigate possible associations between stereotypic motor behavior and cognitive flexibility as measured in the T-maze continuous alternation task (T-CAT). The effect of istradefylline, a selective adenosine A2A receptor antagonist at two doses (10 and 20 mg kg-1  day-1 ) on the expression of stereotypy and T-CAT performance in high (H) and non-(N) stereotypical animals, was investigated in comparison to a control intervention (six groups; n = 8 or 9 per group). No correlation between H behavior and T-CAT performance was found. However, H but not N animals presented with istradefylline-sensitive spontaneous alternation and stereotypy, in that istradefylline at both doses significantly improved the spontaneous alternation scores and attenuated the stereotypical expression of H animals. Thus, evidence is presented that anti-adenosinergic drug action improves repetitive behavior and spontaneous alternation in stereotypical deer mice, putatively pointing to a shared psychobiological construct underlying naturalistic stereotypy and alterations in cognitive flexibility in deer mice.

Peromyscus maniculatus bairdii as a naturalistic mammalian model of obsessive-compulsive disorder: current status and future challenges.

Obsessive-compulsive disorder (OCD) is a prevalent and debilitating condition, characterized by intrusive thoughts and repetitive behavior. Animal models of OCD arguably have the potential to contribute to our understanding of the condition. Deer mice (Permomyscus maniculatus bairdii) are characterized by stereotypic behavior which is reminiscent of OCD symptomology, and which may serve as a naturalistic animal model of this disorder. Moreover, a range of deer mouse repetitive behaviors may be representative of different compulsive-like phenotypes. This paper will review work on deer mouse behavior, and evaluate the extent to which this serves as a valid and useful model of OCD. We argue that findings over the past decade indicate that the deer mouse model has face, construct and predictive validity.

Pathogenesis of Vesicular Stomatitis New Jersey Virus Infection in Deer Mice ( Peromyscus maniculatus) Transmitted by Black Flies ( Simulium vittatum).

The natural transmission of vesicular stomatitis New Jersey virus (VSNJV), an arthropod-borne virus, is not completely understood. Rodents may have a role as reservoir or amplifying hosts. In this study, juvenile and nestling deer mice ( Peromyscus maniculatus) were exposed to VSNJV-infected black fly ( Simulium vittatum) bites followed by a second exposure to naive black flies on the nestling mice. Severe neurological signs were observed in some juvenile mice by 6 to 8 days postinoculation (DPI); viremia was not detected in 25 juvenile deer mice following exposure to VSNJV-infected fly bites. Both juvenile and nestling mice had lesions and viral antigen in the central nervous system (CNS); in juveniles, their distribution suggested that the sensory pathway was the most likely route to the CNS. In contrast, a hematogenous route was probably involved in nestling mice, since all of these mice developed viremia and had widespread antigen distribution in the CNS and other tissues on 2 DPI. VSNJV was recovered from naive flies that fed on viremic nestling mice. This is the first report of viremia in a potential natural host following infection with VSNJV via insect bite and conversely of an insect becoming infected with VSNJV by feeding on a viremic host. These results, along with histopathology and immunohistochemistry, show that nestling mice have widespread dissemination of VSNJV following VSNJV-infected black fly bite and are a potential reservoir or amplifying host for VSNJV.

Of mice and marbles: Novel perspectives on burying behavior as a screening test for psychiatric illness.

Burying forms part of the normal behavioral routine of rodents, although its expression is species-specific. However, it has been suggested that aberrant burying behavior, of which marble-burying (MB) is an example, may represent neophobic and/or compulsive-like behavior. In the present investigation, we assessed MB in an established animal model of obsessive-compulsive disorder (OCD)-namely, spontaneous stereotypy in the deer mouse-to establish whether high (H) stereotypy is associated with neophobia and/or another compulsive endophenotype, i.e. MB, as compared to nonstereotypical (N) controls. A three-trial, one-zone MB test was performed over three consecutive evenings both before and after chronic treatment with high-dose (50 mg/kg/day) oral escitalopram. Neophobia was measured via the number of marbles buried during the first pre- and posttreatment MB trials, and compulsive-like behavior via the number of marbles buried over all pre- and posttreatment MB trials. The data from the present study support earlier findings that burying is a normal behavioral routine (inherent burying behavior, IBB) that is expressed by all deer mice, irrespective of stereotypical cohort, and is not associated with either neophobia or compulsiveness. Indeed, chronic escitalopram treatment, which is similarly effective in treating clinical anxiety and OCD, as well as in attenuating H behavior, failed to influence IBB. Although 11 % of the animals presented with a unique burying endophenotype (high burying behavior), escitalopram also failed to attenuate said behavior, necessitating further investigation as to its relevance. In conclusion, MB cannot be regarded as a measure of anxiety-like or compulsive behavior in the deer mouse model of OCD.

Molecular epidemiology of Bartonella species isolated from ground squirrels and other rodents in northern California.

Bartonella spp. are endemic in wild rodents in many parts of the world. A study conducted in two northern California counties (Sonoma and Yolo) sampling California ground squirrels (Otospermophilus beecheyi) and four other rodent species (Peromyscus maniculatus, P. boylii, P. truei and Neotoma fuscipes) led to the isolation of small Gram-negative bacilli which were identified as Bartonella spp. based on colony morphology, polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and partial gene sequencing. Overall, Bartonella spp. were isolated from the blood of 71% (32/45) of the ground squirrels and one third (22/66) of the other rodents. PCR-RFLP analysis of the gltA and 16S rRNA genes yielded seven unique profiles, four for the ground squirrels and three for the other rodents. Isolates from each PCR-RFLP profiles were submitted for partial sequencing. Ground squirrel isolates were most closely related to B. washoensis, whereas the other rodent isolates were closest to B. vinsonii subsp. vinsonii and B. vinsonii subsp. arupensis. Two of these three species or subspecies are known zoonotic agents.

Higher offspring mortality in deer mice (Peromyscus maniculatus bairdii) that spontaneously present with large nest building behaviour.

Nesting is a normal, evolutionary conserved rodent behavioural phenotype that is expressed for purposes of breeding, safety, and thermal regulation. Further, nesting is commonly assessed as marker of overall rodent health and wellbeing, with poorer nesting performance generally proposed to resemble a worse state of health. Deer mice can be bidirectionally separated with 30 % of mice presenting with excessively large nesting behaviour (LNB). All laboratory-housed deer mice are exposed to identical environmental conditions. Thus, the functional purpose of LNB remains unknown. Considering the evolutionary functions of nesting, we hypothesized that LNB will be related to an inflated drive to breed and nurse offspring. After breeding two generations of offspring from six 'normal' nesting (NNB) and seven LNB expressing pairs, our data showed that while as fertile as NNB expressing pairs, offspring survival of LNB mice were notably worse (67.9 % vs. 98.3 %). In conclusion, variance in nesting behaviour should be considered when animal health and wellbeing is considered, since it may point to underlying biobehavioural perturbations.

Differential impact of pegfilgrastim, a recombinant human granulocyte colony stimulating factor, on the neutrophil count of male and female deer mice (Peromyscus maniculatus bairdii).

BACKGROUND: An increasing body of research implicates inflammatory processes, including alterations in the neutrophil-lymphocyte ratio (NLR), in the pathophysiology of psychiatric illness. The deer mouse (Peromyscus maniculatus bairdii) is commonly studied for its naturalistic expression of compulsive-like behaviour. Towards future efforts to gain an understanding of how innate and adaptive immune processes might be involved in this model, we aimed to study the effects of pegfilgrastim, a pegylated recombinant human granulocyte colony-stimulating factor (g-CSF) analogue, on the NLR of both male and female deer mice. METHODS: Briefly, 54 deer mice (equally distributed between sexes) were exposed to a single injection with either control or pegfilgrastim (0.1 or 1 mg/kg) (n = 18 per group). Six mice of each group (three per sex) were euthanized on days two, four and seven post-administration, their blood collected and the NLR calculated. Data were analysed by means of ordinary three-way ANOVA, followed by Bonferroni post-hoc testing. RESULTS: Irrespective of dose, pegfilgrastim resulted in higher NLR values in mice of both sexes at days four and seven of testing. However, female mice exposed to the higher dose, presented with significantly higher NLR values irrespective of time, compared to male mice exposed to the same. CONCLUSION: The data generated from this work highlight important dose- and sex-specific aspects of pegfilgrastim with female mice showing heighted elevation of the NLR in response to high-dose pegfilgrastim administration only. Since the innate immune components of male and female deer mice is differentially sensitive to g-CSF stimulation, our results provide a useful basis for further study of sex-specific immunological processes in deer mice.

Deer mouse hemoglobin exhibits a lowered oxygen affinity owing to mobility of the E helix.

The deer mouse, Peromyscus maniculatus, exhibits altitude-associated variation in hemoglobin oxygen affinity. To examine the structural basis of this functional variation, the structure of the hemoglobin was solved. Recombinant hemoglobin was expressed in Escherichia coli and was purified by ion-exchange chromatography. Recombinant hemoglobin was crystallized by the hanging-drop vapor-diffusion method using polyethylene glycol as a precipitant. The obtained orthorhombic crystal contained two subunits in the asymmetric unit. The refined structure was interpreted as the aquo-met form. Structural comparisons were performed among hemoglobins from deer mouse, house mouse and human. In contrast to human hemoglobin, deer mouse hemoglobin lacks the hydrogen bond between α1Trp14 in the A helix and α1Thr67 in the E helix owing to the Thr67Ala substitution. In addition, deer mouse hemoglobin has a unique hydrogen bond at the α1ß1 interface between residues α1Cys34 and ß1Ser128.

Striatal adenosine A2A receptor involvement in normal and large nest building deer mice: Perspectives on compulsivity and anxiety.

Obsessive-compulsive disorder (OCD) is characterized by recurring obsessive thoughts and repetitive behaviors that are often associated with anxiety and perturbations in cortico-striatal signaling. Given the suboptimal response of OCD to current serotonergic interventions, there is a need to better understand the psychobiological mechanisms that may underlie the disorder. In this regard, investigations into adenosinergic processes might be fruitful. Indeed, adenosine modulates both anxiety- and motor behavioral output. Thus, we aimed to explore the potential associations between compulsive-like large nest building (LNB) behavior in deer mice, anxiety and adenosinergic processes. From an initial pool of 120 adult deer mice, 34 normal nest building (NNB)- and 32 LNB-expressing mice of both sexes were selected and exposed to either a normal water (wCTRL) or vehicle control (vCTRL), lorazepam (LOR) or istradefylline (ISTRA) for 7- (LOR) or 28 days after which nesting assessment was repeated and animals screened for anxiety-like behavior in an anxiogenic open field. Mice were then euthanized, the striatal tissue removed on ice and the adenosine A2A receptor expression quantified. Our findings indicate that NNB and LNB behavior are not distinctly associated with measures of generalized anxiety and that ISTRA-induced changes in nesting expression are dissociated from changes in anxiety scores. Further, data from this investigation show that nesting in deer mice is directly related to striatal adenosine signaling, and that LNB is founded upon a lower degree of adenosinergic A2A stimulation.

Associations between nesting, stereotypy, and working memory in deer mice: response to levetiracetam.

BACKGROUND: Some deer mice (Peromyscus maniculatus bairdii) exhibit various phenotypes of persistent behaviors. It remains unknown if and how said phenotypes associate with early-life and adult cognitive perturbations, and whether potentially cognitive enhancing drugs might modify such associations. Here, we explored the longitudinal relationship between early-life behavioral flexibility and the expression of persistent behavior in adulthood. We also investigated how said phenotypes might associate with working memory in adulthood, and how this association might respond to chronic exposure to the putative cognitive enhancer, levetiracetam (LEV). METHODS: 76 juvenile deer mice were assessed for habit-proneness in the Barnes maze (BM) and divided into two exposure groups (n = 37-39 per group), i.e., control and LEV (75 mg/kg/day). After 56 days of uninterrupted exposure, mice were screened for nesting and stereotypical behavior, and then assessed for working memory in the T-maze. RESULTS: Juvenile deer mice overwhelmingly utilize habit-like response strategies, regardless of LNB and HS behavior in adulthood. Further, LNB and HS are unrelated in terms of their expression, while LEV reduces the expression of LNB, but bolsters CR (but not VA). Last, an increased level of control over high stereotypical expression may facilitate improved working memory performance. CONCLUSION: LNB, VA and CR, are divergent in terms of their neurocognitive underpinnings. Chronic LEV administration throughout the entire rearing period may be of benefit to some phenotypes, e.g., LNB, but not others (CR). We also show that an increased level of control over the expression of stereotypy may facilitate improved working memory performance.

Lyme Disease Agent Reservoirs Peromyscus leucopus and P. maniculatus Have Natively Inactivated Genes for the High-Affinity Immunoglobulin Gamma Fc Receptor I (CD64).

The abundant and widely distributed deermice Peromyscus leucopus and P. maniculatus are important reservoirs for several different zoonotic agents in North America. For the pathogens they persistently harbor, these species are also examples of the phenomenon of infection tolerance. In the present study a prior observation of absent expression of the high-affinity Fc immunoglobulin gamma receptor I (FcγRI), or CD64, in P. leucopus was confirmed in an experimental infection with Borreliella burgdorferi, a Lyme disease agent. We demonstrate that the null phenotype is attributable to a long-standing inactivation of the Fcgr1 gene in both species by a deletion of the promoter and coding sequence for the signal peptide for FcγRI. The Fcgr1 pseudogene was also documented in the related species P. polionotus. Six other Peromyscus species, including P. californicus, have coding sequences for a full-length FcγRI, including a consensus signal peptide. An inference from reported phenotypes for null Fcgr1 mutations engineered in Mus musculus is that one consequence of pseudogenization of Fcgr1 is comparatively less inflammation during infection than in animals, including humans, with undisrupted, fully active genes.

Seasonal and sex-specific changes in the gastrointestinal tracts of Peromyscus maniculatus.

Functional traits are phenotypic characteristics that contribute to fitness of individuals in dynamic and changing environments. In mammals, both categorical and continuous (e.g., quantitative) functional traits have been extensively utilized as proxies for diet, locomotion, and other aspects of species ecology, but there has been less focus on form and function of soft tissues. This is particularly true for the digestive system, which varies in size and complexity across Class Mammalia and plays a major role in the energetics of species. To guide more effective utilization of gastrointestinal (GI) morphology as a functional proxy in small mammal ecology, we examined how GI tracts (lengths and masses of four GI sections) varied within a population of deer mice (Peromyscus maniculatus) in the Southern Appalachian Mountains of North Carolina, United States. We collected samples of adult P. maniculatus monthly for 1 year and measured GI tracts to quantify variation with respect to seasonality and trophic level, providing insight into plasticity in this soft tissue trait over time. We found that season had a significant effect on the total length and wet mass of the GI tract, with January mice having the longest GI tracts and lengths being shortest in the summer. The relative shortening of the GI tract in summer corresponded with a partial trophic increase detected by stable isotope signatures. GI length and wet mass also were affected by reproduction, but males and females responded in sex-specific ways to demands of reproduction, with reproductively active males having shorter and lighter GI tracts than nonreproductively active males. Our study provides proof-of-concept for understanding population-level plasticity in a rarely collected soft tissue trait, which may also be complementary to standard craniodental measurements as a functional dietary proxy to understand mammalian ecology and community assembly.

Los rasgos funcionales son características fenotípicas que contribuyen a la aptitud de los individuos en entornos dinámicos y cambiantes. En los mamíferos, los rasgos funcionales categóricos y continuos (por ejemplo, cuantitativos) se han utilizado ampliamente como indicadores de la dieta, la locomoción y otros aspectos de la ecología de las especies, a la vez que se ha prestado menos atención a la forma y función de los tejidos blandos. Este es particularmente el caso del sistema digestivo, que varía en tamaño y complejidad a través de la Clase Mammalia, jugando un papel importante en la energética de las especies. Para propiciar una utilización más efectiva de la morfología gastrointestinal (GI) como un rasgo funcional en la ecología de los pequeños mamíferos, examinamos cómo los tractos GIs (longitudes y masas de cuatro secciones GI) variaban dentro de una población de ratones ciervos (Peromyscus maniculatus) de las Montañas Apalaches del sur de Carolina del Norte, Estados Unidos. Mensualmente, durante un año, recolectamos especímenes adultos de P. maniculatus y medimos sus tractos gastrointestinales para cuantificar la variación con respecto a la estacionalidad y el nivel trófico, brindando información sobre la plasticidad en estos rasgos de tejido blando a lo largo del tiempo. Descubrimos que la estacionalidad tiene un efecto significativo en la longitud total y la masa húmeda del tracto gastrointestinal, ya que los ratones de enero tienen los tractos gastrointestinales más largos y las longitudes son más cortas durante el verano. El acortamiento relativo del tracto GI en verano se correspondió con un aumento trófico parcial detectado por las cuantificación de isótopos estables. La longitud GI y la masa húmeda también se vieron afectadas por la reproducción; pero los machos y las hembras respondieron de manera diferente a las demandas de la reproducción. Los machos reproductivamente activos tienen tractos gastrointestinales más cortos y ligeros que los machos no activos reproductivamente. Nuestro estudio constituye un avance para comprender la plasticidad a nivel de población en un rasgo de tejido blando raramente recolectado, que también puede ser complementario a las mediciones craneodentales estándar como un proxy dietético funcional para entender la ecología de los mamíferos y el ensamblaje de la comunidad.

Interspecific variation in cooperative burrowing behavior by Peromyscus mice.

Animals often adjust their behavior according to social context, but the capacity for such behavioral flexibility can vary among species. Here, we test for interspecific variation in behavioral flexibility by comparing burrowing behavior across three species of deer mice (genus Peromyscus) with divergent social systems, ranging from promiscuous (Peromyscus leucopus and Peromyscus maniculatus) to monogamous (Peromyscus polionotus). First, we compared the burrows built by individual mice to those built by pairs of mice in all three species. Although burrow length did not differ in P. leucopus or P. maniculatus, we found that P. polionotus pairs cooperatively constructed burrows that were nearly twice as long as those built by individuals and that opposite-sex pairs dug longer burrows than same-sex pairs. Second, to directly observe cooperative digging behavior in P. polionotus, we designed a burrowing assay in which we could video-record active digging in narrow, transparent enclosures. Using this novel assay, we found, unexpectedly, that neither males nor females spent more time digging with an opposite-sex partner. Rather, we demonstrate that opposite-sex pairs are more socially cohesive and thus more efficient digging partners than same-sex pairs. Together, our study demonstrates how social context can modulate innate behavior and offers insight into how differences in behavioral flexibility may evolve among closely related species.

Methylation studies in Peromyscus: aging, altitude adaptation, and monogamy.

DNA methylation-based biomarkers of aging have been developed for humans and many other mammals and could be used to assess how stress factors impact aging. Deer mice (Peromyscus) are long-living rodents that have emerged as an informative model to study aging, adaptation to extreme environments, and monogamous behavior. In the present study, we have undertaken an exhaustive, genome-wide analysis of DNA methylation in Peromyscus, spanning different species, stocks, sexes, tissues, and age cohorts. We describe DNA methylation-based estimators of age for different species of deer mice based on novel DNA methylation data generated on highly conserved mammalian CpGs measured with a custom array. The multi-tissue epigenetic clock for deer mice was trained on 3 tissues (tail, liver, and brain). Two human-Peromyscus clocks accurately measure age and relative age, respectively. We present CpGs and enriched pathways that relate to different conditions such as chronological age, high altitude, and monogamous behavior. Overall, this study provides a first step towards studying the epigenetic correlates of monogamous behavior and adaptation to high altitude in Peromyscus. The human-Peromyscus epigenetic clocks are expected to provide a significant boost to the attractiveness of Peromyscus as a biological model.