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PubMed1982

Evidence for a brain site of melatonin action in the white-footed mouse, Peromyscus leucopus.

A brain site of melatonin action has been determined for the white-footed mouse (Peromyscus leucopus). Melatonin-beeswax implants releasing small quantities of melatonin (less than 100 ng/day) caused a 50% reduction in reproductive tract weight relative to controls (p less than 0.025) with 83% of these animals having an imperforate vagina, when implanted in the anterior hypothalamic nuclei (AH) and suprachiasmatic nuclei (SCN). Subcutaneous implants had little effect. Implants in the AH and SCN also had a pronounced effect on both lipid-free interscapular brown fat and nesting behavior. Mice implanted in these regions exhibited a 59% increase in interscapular brown fat and 65% more nesting than controls (both p less than 0.01). These results suggest that melatonin acts at a region in the anterior hypothalamus which controls photoperiodic adjustments.

Adipose Tissue, Brown↗
PubMed1982

Diurnal rhythm of response to chronic intrahypothalamic melatonin injections in the white-footed mouse, peromyscus leucopus.

A pronounced diurnal change in responsiveness to intrahypothalamic melatonin injections was observed in the white-footed mouse, Peromyscus leucopus. 7 weeks of chronic daily afternoon (12 h after lights-on) injections of 500 ng melatonin into the vicinity of the suprachiasmatic nuclei (SCN) caused a 66% reduction in female reproductive tract weight relative to saline-injected controls (p less than 0.01), with 83% of these animals having an imperforate vagina, and no animals having mature follicles. Subcutaneous injections of 500 ng melatonin had little effect. Chronic morning (2 h after lights-on) injections of melatonin into the vicinity of the SCN had little effect on the maintenance of normal reproductive tract weight, with 18% of these animals having an imperforate vagina, and 71% having mature follicles. These results indicate that the daily rhythm of melatonin antigonadal action is due to change in responsiveness to melatonin of target neurons in the region of the SCN.

Animals↗
PubMed1986

Gonadotropin-releasing hormone neuronal system of the white-footed mouse, Peromyscus leucopus.

The cytoarchitecture of the gonadotropin-releasing hormone (GnRH) neuronal system of the female white-footed mouse (Peromyscus leucopus) was characterized using immunocytochemical procedures on thick vibratome sections. Most of the labelled cell bodies are organized loosely into three groups associated with the periventricular region of the medial preoptic area, the diagonal band of Broca, and the olfactory peduncle. A small number of cells are scattered throughout the medial septum, retrochiasmatic area, and in the posterior hypothalamus, lateral from the median eminence (ME). Labelled fibers are distributed widely throughout the brain, with heavy concentrations within the ME and the organum vasculosum of the lamina terminalis (OVLT). A subchiasmatic pathway for GnRH fibers, which courses from the OVLT to the ME, was identified. Fiber plexuses are present in the olfactory bulbs, accessory olfactory bulbs, triangular nucleus of the septum, medial habenular nucleus, and the amygdala. The ependymal layer of the third ventricle that is associated with the ME and OVLT contains large numbers of GnRH fibers, some of which appear to extend into the ventricular lumen. The wide dispersion of the GnRH neuronal system throughout the brain of P. leucopus is evidence that, in addition to its role as a gonadotropin-releasing hormone, GnRH may have a neurophysiologic function in the central nervous system of this species.

Animals↗
PubMed1977

Chromosomes of Peromyscus (rodentia, cricetidae). VI. The genomic size.

In the genus Peromyscus cells of all species contain 48 chromosomes; however, the fundamental number varies from 56 (P. Crinitus, P. boylei) to 96 (P. eremicus). In some cases biarmed chromosomes are the result of pericentric inversions, while in others they are the result of addition of large amounts of constitutive heterochromatin. Flow microfluorometric DNA-per-cell determinations demonstrated that in some species (P. eremicus) the genome is increased by 36% over the amount of DNA found in most mammalian species. Studies of unique karyotypes with increased amounts of DNA added as constitutive heterochromatin may ultimately help in the elucidation of the mechanisms involved in karyotype evolution and speciation.

Animals↗
PubMed1981

An assessment of the nature of chromosomal rearrangements in 18 species of Peromyscus (Rodentia: Cricetidae).

G- and C-banded karyotypes from 9 previously unstudied species of Peromyscus are described and compared to the 9 species described in the literature. Additional new data are presented for P. eremicus. A hypothetical evolutionary tree for the 18 species was constructed based on the assumption that, where possible, shared chromosomal rearrangements became established in a common ancestor. A minimum of 60 chromosomal rearrangements (34 heterochromatic additions and 26 pericentric inversions) were needed to construct the most parsimonious tree. Seven of the 18 species have heterochromatin in noncentromeric areas. Three times as many inversions have been identified in the 11 largest pairs as have been observed in the 12 smallest pairs. Peromyscine rodents are characterized by a pattern of chromosomal variation quite distinct from that described for other rodent genera, such as Sigmodon and Mus. Karyotypic orthoselection in rodents appears to be relatively common in closely related species.

Animals↗
PubMed1984

Evidence for heterosynaptic pairing of the inverted segment in pericentric inversion heterozygotes of the deer mouse (Peromyscus maniculatus).

Silver-stained pachytene cells of male deer mice, Peromyscus maniculatus, which were heterozygous for a naturally occurring pericentric inversion of chromosome 6, were analyzed by light microscopy. The presence of the terminally positioned inversion, involving approximately 30% of the length of chromosome 6, was detected by G-banding. Within the inversion, C-band-positive heterochromatin was restricted to the centromeric region. Silver-staining of spermatocytes revealed the synaptonemal complexes (SCs) of the autosomal bivalents and the X-Y chromosome association. Pachytene cells were scored for the presence of inversion loops corresponding to the pericentric inversion of chromosome 6. Possible loop 6 configurations were detected in less than 1% of the cells examined, the vast majority of cells having regularly formed autosomal SCs similar to those reported for homomorphic chromosome pairs in other rodent species. It appears, therefore, that in these mice the inverted region of chromosome 6 was heterosynaptic throughout pachytene. Heterosynapsis is hypothesized as a mechanism which might obviate the production of duplication and deletion chromatids expected from crossing-over in pericentric inversion loops. The observation of heterosynaptic pairing in the inverted segment and the hypothesis of inversion heterosynapsis as a mechanism averting gametic loss are consistent with the widespread occurrence of pericentric inversion polymorphisms in P maniculatus and the apparent failure of pericentric inversions to genetically isolate populations of this species.

Animals↗
PubMed1995

Assignment of Tp53 and Tk1 to chromosome 13 in Peromyscus by fluorescence in situ hybridization.

Mus domesticus DNA probes for the tumor suppressor protein-53 (Tp53) and thymidine kinase-1 (Tk1) genetic loci were used to identify clones representing these loci in a Peromyscus leucopus (white-footed mouse) cosmid library. The cosmid-derived homologous probes were biotinylated and hybridized to P. maniculatus (deer mouse) chromosomes. Probes for both genes hybridized to the chromosome 13 pair identified by prior G-banding. Deer mouse chromosome 13 shares a region of homology with mouse chromosome 11, rat chromosome 10 and human chromosome 17.

Animals↗
PubMed1984

Pathogenesis of Trypanosoma brucei infection in deer mice (Peromyscus maniculatus). Ultrastructural pathology of the spleen, liver, heart, and kidney.

Trypanosoma brucei EATRO 110 infection of the deer mice (Peromyscus maniculatus) produced moderate to marked lesions in the spleen, liver, heart, and kidney seven to ten weeks after infection. Splenic lesions consisted of marked splenomegaly, with infected spleens weighing 25.9 times control spleens. Transmission electron microscopy of the sinuses and Billroth's cords of the splenic red pulp demonstrated an increased cellularity with greater contact between cells due partly to proliferation of macrophages, transformed lymphocytes and plasma cells and partly to accelerated erythropoiesis with increases in the numbers of rubricytes and reticulocytes. Erythrocytes also were present in large numbers, and erythroclasis was accelerated. Hepatic lesions consisted of necrosis of few hepatocytes, proliferation and hypertrophy of Kupffer's cells which exhibited increased phagocytosis--particularly of erythrocytes, as well as perivascular cuffs consisting of lymphocytes, plasma cells and macrophages. Myocarditis was marked and was characterized by degeneration of myocardial fibers with decreases in mitochondrial size and myofibril contents and fragmentation of some degenerating fibers, and was accompanied by accumulation of inflammatory cells including lymphocytes, transformed lymphocytes, plasma cells, and macrophages between the myocardial fibers. Renal lesions consisted of severe glomerulonephritis characterized by deposition of electron dense material along the basement membrane and in the mesangium of the glomerular tufts, and less frequently beneath the basement membrane and visceral epithelium of the Bowman's capsule and within the peritubular vessels. Neutrophils with fewer macrophages and lymphocytes invaded the glomeruli.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

Pathogenesis of Trypanosoma brucei infection in deer mice (Peromyscus maniculatus). Light and electron microscopic study of testicular lesions.

The results of light and electron microscopic studies demonstrated that Trypanosoma brucei infection produced marked testicular degeneration in deer mice (Peromyscus maniculatus) with highly significant (p less than 0.001) decreases in testicular weight, seminiferous tubular diameter, and epithelial thickness. Lesions in seminiferous tubules consisted of necrosis of spermatids, spermatocytes, and sometimes the spermatogonia. Sertoli's cells had marked vacuolation and accumulation of phagocytic material. Orchitis was present in most infected mice, particularly those with severe seminiferous tubular degeneration. There was marked folding of the basal laminae of the seminiferous tubule and myoid layer, and a consistent increase in the layers of the basal laminae of the seminiferous tubule. Trypanosomes were present in the intertubular tissues of seminiferous tubules, and they occasionally crossed the myoid layer but never the basal lamina of seminiferous tubules. Inflammatory and other cells in the interstitium consisted of lymphocytes (35.2%), Leydig's cells (25.1%), macrophages (18.1%), plasma cells (12.3%), neutrophils (5.6%), eosinophils (3.2%), and mast cells (0.5%). Inflammatory cells including lymphocytes (51.6%), macrophages (43.9%), plasma cells (3.0%), and eosinophils (1.5%) occasionally breached the myoid layer and occupied the space between it and the basal lamina of the seminiferous tubule. Leydig's cells usually existed in clusters, had decreased mitochondrial size and secretory granules, and folding of the nuclear membrane.

Animals↗
PubMed2000

Tau differences between short-day responsive and short-day nonresponsive white-footed mice (Peromyscus leucopus) do not affect reproductive photoresponsiveness.

In laboratory-bred rodent populations, intraspecific variation in circadian system organization is a known cause of individual variation in reproductive photoresponsiveness. The authors sought to determine whether circadian system variation accounted for individual variation in reproductive photoresponsiveness in a single, highly genetically variable population of Peromyscus leucopus recently derived from the wild. Running-wheel activity patterns of male and female mice, aged 70 to 90 days, from artificially selected lines of reproductively photoresponsive (R) and nonresponsive (NR) lines were monitored under short-day photoperiod (8 h light, 16 h dark), long-day photoperiod (16 h light, 8 h dark), and constant darkness (DD). NR mice displayed a significantly longer mean free-running period (24.08 h) in DD compared with R mice (23.75 h), due in large part to a difference between NR and R females (24.25 h vs. 23.74 h, respectively). All other entrainment characteristics (alpha, phase angle of activity) under short days, long days, and DD were similar between R and NR mice. Variation in free-running period and entrainment characteristics has been shown to affect photoresponsiveness in other rodent species by altering the manner in which the circadian system interprets short days. To determine whether variation in photoresponsiveness in P. leucopus is due to differences in free-running period instead of variation downstream from the central circadian clock in the pathway controlling photoresponsiveness, the authors exposed young R and NR mice to DD and measured the effect on reproductive organ development. If variation in free-running period affected how the circadian system of mice interpreted short days, then both R and NR mice exposed to DD should have exhibited a delay in gonadal development. Only R mice exhibited pubertal delay in DD. NR mice exhibited large paired testes, paired seminal vesicles, paired ovaries, and uterine weight typical of mice nonresponsive to short days, whereas R mice exhibited reproductive organ weight typical of mice responsive to short days. These data suggest that despite significant differences in free-running period between R and NR mice, individual variation in photoresponsiveness is not due to differences in how the circadian systems of R and NR mice interpret the LD cycle.

Animals↗
PubMed1993

Winter adaptations of male deer mice (Peromyscus maniculatus) and prairie voles (Microtus ochrogaster) that vary in reproductive responsiveness to photoperiod.

Individuals of many nontropical rodent species restrict breeding to the spring and summer. Seasonal reproductive quiescence putatively reflects the energetic incompatibility of breeding and thermoregulatory activities. However, so-called "out-of-season" breeding occurs in virtually all rodent populations examined, suggesting that the incompatibility can be resolved. Both reproductive inhibition and development of energy-saving adaptations are mediated by environmental photoperiod, but some individuals do not inhibit reproduction in short days. In order to assess the costs and benefits of winter breeding, the present study examined the extent to which male prairie voles (Microtus ochrogaster) and deer mice (Peromyscus maniculatus) that maintained summer reproductive function in winter-simulated daylengths also maintained summer thermoregulatory adaptations. Circadian locomotor activity patterns, basal metabolic rate, capacity for nonshivering thermogenesis, nest building, body mass, and daily food consumption were compared among short-day (LD 8:16) regressed males, short-day (LD 8:16) nonregressed males, and long-day (LD 16:8) males. Short-day nonregressed deer mice resembled long-day conspecifics in terms of body mass and nest-building activities; however, the locomotor activity pattern of short-day nonregressed deer mice was similar to that of their short-day regressed conspecifics. Short-day nonregressed prairie voles had body masses similar to those of long-day conspecifics. Regardless of their reproductive response to photoperiod, short-day prairie voles reduced their daily food consumption and wheel-running activity, compared to long-day voles. These results suggest that winter breeding has energetic costs, most likely resulting from maintaining a "summer-like" body mass relative to that of reproductively regressed animals. These costs may be ameliorated to some extent by the reduction in locomotor activity and nest-building behavior emitted by short-day animals, regardless of reproductive response to short days. Thus, the occurrence of winter breeding may be the result of sufficient numbers of reproductively photoperiod-nonresponsive morphs in the population and sufficiently mild ambient conditions to permit survival of these larger animals.

Adaptation, Physiological↗
PubMed1996

Photoperiod and temperature interact to affect immune parameters in adult male deer mice (Peromyscus maniculatus).

Nontropical rodents often experience large seasonal fluctuations in both food availability and energy demands. The energy required for thermoregulation is highest during the winter when food availability may be at an annual minimum. Failure to cope with winter probably accounts, in part, for the increased prevalence of disease and death relative to that in summer. Winter conditions may elevate circulating glucocorticosteroid levels, which can compromise immune function. To increase the odds of surviving the energetic demands of winter, individuals of some rodent species appear to enhance immune function before conditions deteriorate. Previous laboratory studies suggest that immune enhancement can be induced by short days. These findings contrast with the results of several field studies reporting suppressed immune function during the winter. To resolve this conflict, the authors hypothesized that winter stressors present in field studies counteracted the short-day enhancement of immune function reported in laboratory studies. If true, then immune function of captive mice in short days should be compromised by low temperature or reduced food availability. Both ambient temperature and photoperiod were manipulated in the present study to assess their effects on immune parameters in male deer mice (Peromyscus maniculatus). Animals in short days regressed their reproductive systems and also displayed significantly higher immunoglobulin G (IgG) levels than did those in long days. Deer mice maintained in low temperatures had significantly reduced splenic masses and basal IgG levels independent of day length. Animals maintained in both short days and low temperatures displayed IgG levels comparable to those of mice in long-day/mild-temperature conditions. Animals maintained in long days and low temperatures had significantly higher serum corticosterone levels than did animals maintained in long days at mild temperatures. These data are consistent with the hypothesis that immune parameters are enhanced in short days to counteract stress-mediated immune suppression occurring during the winter.

Adipose Tissue↗
PubMed1998

Exogenous melatonin enhances cell-mediated, but not humoral, immune function in adult male deer mice (Peromyscus maniculatus).

Many nontropical rodent species display seasonal changes in reproductive physiology and metabolism, as well as in immune function. Field studies of seasonal changes in immune function typically report decreased immune function in the short days of winter compared to summer; presumably, reduced immunity in winter reflects increased glucocorticoid secretion in response to environmental stressors. In contrast, laboratory studies of photoperiodic changes in immunity invariably demonstrate increased immune function in short compared to long days. Although the precise mechanisms regulating short-day enhancement of immune function are not known, it is hypothesized that increased immunity is due to the increased duration of melatonin secretion in short compared to long days. However, melatonin can act both directly (i.e, via melatonin receptors located on lymphatic tissue) and indirectly (i.e., via alterations in gonadal steroids) to affect immune function. The present study examined the effects of exogenous melatonin administration on both cell-mediated and humoral immune function in adult male deer mice (Peromyscus maniculatus), as well as the role of gonadal steroid hormones in mediating these effects. Mice either were castrated to remove circulating androgens or received sham operations and were implanted with empty capsules or capsules containing melatonin. Individual mice implanted with melatonin underwent reproductive regression and displayed enhanced splenocyte proliferation to the T-cell mitogen concanavalin A; antigen-specific serum immunoglobulin M production was unaffected by melatonin treatment. Castration had no effect on either cell-mediated or humoral immune function. Taken together, these results suggest that exogenous melatonin enhances cell-mediated, but not humoral, immune function in adult male deer mice and that this effect is independent of gonadal steroid hormones. These results are consistent with a direct effect of melatonin on immunity.

Analysis of Variance↗
PubMed1998

Photoperiod, ambient temperature, and food availability interact to affect reproductive and immune function in adult male deer mice (Peromyscus maniculatus).

Winter is often stressful. Increased energetic demands in winter and concurrent reductions in energy availability can lead to an energetic imbalance and compromise survival. To increase the odds of surviving winter, individuals of some nontropical rodent species have evolved mechanisms to enhance immune function in advance of harsh winter conditions. Short day lengths provide a proximate cue for enhancement of immune function, an adaptive functional response to counter environmental stress-induced reduction in immune function. In the present study, photoperiod, ambient temperature, and food availability were manipulated and reproductive function and cell-mediated immunity were assessed in adult male deer mice (Peromyscus maniculatus). Mice maintained in short days regressed their reproductive systems and displayed enhanced immune function compared to long-day animals. Reduced food availability elevated corticosterone concentrations and suppressed reproductive and immune function, whereas ambient temperature alone had no effect on cell-mediated immunity. The suppressive effect of food restriction on reproductive and immune function was overcome by maintaining animals in short days. However, short-day, food-restricted mice maintained at low ambient temperatures displayed reduced reproductive and immune function compared to animals maintained at mild temperatures. Taken together, these results suggest that short-day enhancement of immune function can counteract some, but not all, of the immunosuppressive effects of winter stressors. These data are consistent with the hypothesis that immune function is enhanced in short days to counteract stress-mediated immune suppression occurring during winter.

Adipose Tissue↗
PubMed2004

Cloning and characterization of deer mouse (Peromyscus maniculatus) cytokine and chemokine cDNAs.

BACKGROUND: Sin Nombre virus (SNV) establishes a persistent infection in the deer mouse, Peromyscus maniculatus. A strong antibody response occurs in response to SNV infection, but the role of the innate immune response is unclear. To address this issue, we have initiated an effort to identify and characterize deer mouse cytokine and chemokine genes. Such cytokines and chemokines are involved in various aspects of immunity, including the transition from innate to adaptive responses, type I and type II responses, recruitment of leukocytes to sites of infection, and production of mature cells from bone marrow progenitors. RESULTS: We established a colony of SNV antibody-negative deer mice and cloned 11 cytokine and chemokine partial cDNA sequences using directed PCR. Most of the deer mouse sequences were highly conserved with orthologous sequences from other rodent species and functional domains were identified in each putative polypeptide. CONCLUSIONS: The availability of these sequences will allow the examination of the role of these cytokines in deer mouse responses to infection with Sin Nombre virus.

Amino Acid Sequence↗
PubMed2004

Generation of competent bone marrow-derived antigen presenting cells from the deer mouse (Peromyscus maniculatus).

BACKGROUND: Human infections with Sin Nombre virus (SNV) and related New World hantaviruses often lead to hantavirus cardiopulmonary syndrome (HCPS), a sometimes fatal illness. Lungs of patients who die from HCPS exhibit cytokine-producing mononuclear infiltrates and pronounced pulmonary inflammation. Deer mice (Peromyscus maniculatus) are the principal natural hosts of SNV, in which the virus establishes life-long persistence without conspicuous pathology. Little is known about the mechanisms SNV employs to evade the immune response of deer mice, and experimental examination of this question has been difficult because of a lack of methodologies for examining such responses during infection. One such deficiency is our inability to characterize T cell responses because susceptible syngeneic deer mice are not available. RESULTS: To solve this problem, we have developed an in vitro method of expanding and generating competent antigen presenting cells (APC) from deer mouse bone marrow using commercially-available house mouse (Mus musculus) granulocyte-macrophage colony stimulating factor. These cells are capable of processing and presenting soluble protein to antigen-specific autologous helper T cells in vitro. Inclusion of antigen-specific deer mouse antibody augments T cell stimulation, presumably through Fc receptor-mediated endocytosis. CONCLUSIONS: The use of these APC has allowed us to dramatically expand deer mouse helper T cells in culture and should permit extensive characterization of T cell epitopes. Considering the evolutionary divergence between deer mice and house mice, it is probable that this method will be useful to other investigators using unconventional models of rodent-borne diseases.

Animals↗
PubMed1999

Short photoperiods evoke testicular apoptosis in white-footed mice (Peromyscus leucopus).

Many small, nontropical mammals stop breeding during winter. Chronic exposure of males to short days (<12.5 h light/day) causes the testes to atrophy and both steroidogenesis and gametogenesis to decrease. Male white-footed mice (Peromyscus leucopus) exposed to inhibitory short day lengths provide a natural animal model to study the cellular mechanisms regulating testicular regression. In the present study, the possible role of apoptosis was assessed during naturally occurring, short day-induced gonadal regression in white-footed mice by in situ terminal transferase-mediated end labeling (TUNEL), quantitative DNA 3'-end-labeling autoradiography (laddering) of DNA fragments, and quantification of Fas protein expression, an early initiator of apoptosis. Sexually mature male mice were exposed to short (8 h of light, 16 h of darkness) or long (16 h of light, 8 h of darkness) day lengths for 2, 4, 6, 8, or 10 weeks; gonads were then removed and processed for detection of apoptotic activity. In common with previous studies, the first significant reduction in relative testis mass was observed at week 10 of short day exposure. A 2- to 3-fold increase in apoptotic (TUNEL-positive) germ cells per seminiferous tubule was observed in the testes of mice exposed to short days for 4, 6, 8, or 10 weeks compared with the testes of long day animals. The extent of 3'-end labeling of low mol wt DNA increased with 4-8 weeks of short day exposure. Western blot analysis revealed an up-regulation of the Fas protein in the testes of short day males at 4, 8, and 10 weeks. Fas staining was primarily localized to spermatocytes and spermatids. Plasma testosterone concentrations decreased in short compared with long day animals after 6, 8, or 10 weeks. The increase in TUNEL positive-labeled germ cells, testicular DNA fragmentation, and up-regulation of the Fas protein before short day reductions of testis mass and function suggest that apoptosis is important for the mediation of photoperiod-induced testicular regression in white-footed mice.

Animals↗
PubMed2004

Cold-acclimation in Peromyscus: temporal effects and individual variation in maximum metabolism and ventilatory traits.

Thermal acclimation in small endotherms provides an excellent model for the study of physiological plasticity, as energy requirements can be easily manipulated and the results are relevant for natural conditions. Nevertheless, how physiology changes throughout acclimation, and how individuals vary in their response to acclimation, remain poorly understood. Here we describe a high temporal-resolution study of cold acclimation in the deer mouse Peromyscus maniculatus. The experimental design was based on repeated measures at short intervals throughout cold acclimation, with controls (maintained at constant temperature) for measurement artifacts. We monitored body mass, maximum metabolic rate in cold exposure and ventilatory traits (respiratory frequency, tidal and minute volume and oxygen extraction) for 3 weeks at 23 degrees C. Then, half of the individuals were held for 7 weeks at 5 degrees C. Body mass was differently affected by cold acclimation depending on sex. Maximal metabolism ((O(2)max)) increased significantly during the first week of cold acclimation, "overshot" after 5 weeks and dropped to a plateau about 34% above control values at week 7. Similarly, ventilatory traits increased during cold acclimation, though responses were different in their kinetics and magnitude. Body mass, maximum metabolism, and most ventilatory traits were repeatable after 7 weeks in control and cold-acclimated animals. However, repeatability tended to be lower in the cold-acclimated group, especially while animals were still acclimating. Our results show that acclimation effects may be under- and/or overestimated, depending on when trials are performed, and that different traits respond differently, and at different rates, to acclimation. Hence, future studies should be designed to ensure that animals have attained steady-state values in acclimation experiments.

Acclimatization↗