In vitro fertilization of two species of deer mouse eggs by homologous or heterologous sperm and penetration of laboratory mouse eggs by deer mouse sperm

Newly ovulated eggs from immature deer mice (Peromyscus maniculatus and P. polionotus) and mature laboratory mice (Mus musculus) treated with PMSG and HCG were inseminated in vitro with spermatozoa recovered from the cauda epididymidis of mature males. The time required for capacitation of deer mouse sperm in culture was estimated to be about two to five hours based on the dispersal of sperm agglutination and increase of sperm motility. The rate of sperm penetration through the zona pellucida of deer mouse eggs by homologous or heterologous sperm was relatively high (72-91%) but that of laboratory mouse eggs by deer mouse sperm was low (20-21%). After penetration through the zona pellucida, a high proportion of deer mouse eggs (79-93%) were fertilized by homologous or heterologous deer mouse sperm but no laboratory mouse eggs were fertilized by sperm of two species of deer mice. The zona pellucida was dissolved in a higher proportion of laboratory mouse eggs cultured with P. maniculatus (45%) than with P. polionotus sperm (3.4%), but this did not happen by incubation of deer mouse eggs with homologous or heterologous sperm. It seems that there is little difference in sperm penetration and fertilization between these two closely related species of deer mice but the reactions between the mouse eggs and deer mouse sperm are quite different.     

Phenotypic differences in the GnRH neuronal system of deer mice Peromyscus maniculatus under a natural short photoperiod

The neural mechanisms by which short photoperiod induces gonadal regression among seasonally breeding mammals are not well understood. One hypothesis suggests that the proximate cause of seasonal gonadal regression is a photoperiod-induced modification in GnRH secretion. This hypothesis is indirectly supported by our recent findings using immunocytochemistry which identified specific photoperiod-induced adjustments in the number and morphology of GnRH containing neurones between reproductively competent and reproductively regressed laboratory housed male deer mice. Herein, we report that the GnRH neuronal system is similarly affected in reproductively responsive and nonresponsive wild male deer mice Peromyscus maniculatus exposed to a natural short photoperiod. The distribution of immunoreactive (IR)-GnRH neurones was nearly identical in field caught animals and those housed under artificial photoperiod in the laboratory. Compared with reproductively nonresponsive males, reproductively responsive mice from the field population possessed a greater total number of IR-GnRH neurones, a greater number of IR-GnRH neurones within the lateral hypothalamus, and a greater proportion of bipolar IR-GnRH neurones. Each of these distributional and morphological characters was consistent with our findings in laboratory housed male deer mice exposed to an artificial short photoperiod. Taken together, these data underscore the validity of using an artificial photoperiod to evaluate seasonal adjustments in reproductive function in the laboratory.     

Intra- and interspecies comparison of sperm migration through polyacrylamide gel as an index of spermatozoal viability

Sperm migration distance through a polyacrylamide gel mimicking cervical mucus was compared among seven species: dog, cat, goat, ram, clouded leopard, dorcas gazelle, and Eld's deer. Freshly collected spermatozoa were evaluated microscopically and then assayed for migration distance in gel-filled capillary tubes in raw or diluted concentrations or after longevity declines in sperm motility and progressive status. Sperm count per milliliter of ejaculate and sperm percent motility ratings varied (P < 0.05) among selected species. Undiluted ejaculated spermatozoa from all species, except the clouded leopard, penetrated the polyacrylamide gel. Migration distance (mm) was different (P < 0.05) among species and not clearly correlated to concentration or motility factors. Although sperm concentrations in the dog and Eld's deer were similar, average migration distance of deer sperm was more than fourfold greater (P < 0.01) than that of dog sperm. The sperm motility rating for the gazelle was greater (P < 0.05) than that for the cat; however, penetration distance in the cat was more than twice as great (P < 0.05) as that in the gazelle. Species also varied in migration response after altering sperm concentration: Halving the sperm count of the dog, gazelle, and Eld's deer had no effect, but the same procedure decreased (P < 0.05) penetration distance in the goat and ram. No migration was observed in any species at a sperm concentration of 25 × 10⁶ cells or less. Within species a decline in sperm percent motility-progressive status ratings was correlated (P < 0.05) to a subsequent decrease in penetration distance. These results provide a comparative assessment of sperm cell migration through a synthetic cervical mucus and suggest that this test may be a useful adjunct in evaluating reproductive potential. However, the assay is specific in interpretive merit, as sperm penetration distance within a single batch of gel is markedly variant among species and in some species dependent on sperm concentration. This interspecies specificity in sperm migration through a homogeneous gel suggests intrinsic species variance in sperm cell-cervical mucus interaction, suggesting that this assay could be valuable in future studies of the mechanism of sperm transport.     

Development of in vitro embryo production systems for red deer (Cervus elaphus). Part 1. Effect of epithelial oviductal monolayers and heparin on in vitro sperm motility and penetration of in vitro matured oocytes

In vitro fertilisation (IVF) protocols for red deer have yielded low fertilisation rates, with no embryo development beyond the eight-cell stage when heparin was used as the in vitro capacitation agent. As this low fertilisation rate may result from reduced motility, the present study investigated the use of red deer oviduct epithelial cell monolayers (COEM) and conditioned medium (Cm) from the monolayers to maintain red deer sperm motility in vitro. A second experiment compared the fertilisability of red deer sperm pre-incubated for 4-12h on COEM or for 4h in TALP medium supplemented with 20 microg of heparin.COEM was superior in maintaining red deer sperm motility compared with either Sp-TALP alone or Cm (P<0.05). COEM sustained sperm motility at levels comparable to the initial motility over the 24h period. The motility of sperm incubated in Sp-TALP and Cm was similar and had declined to less than 10% by 4h and no motile sperm were observed by 8h. Overall, the penetration rates of in vitro red deer oocytes were low (5-28%) regardless of sperm treatment. Sperm pre-incubated on COEM penetrated more oocytes than sperm incubated with heparin (P<0.001). Penetration rates were similar for 4-12h pre-incubation of sperm on COEM (P>0.50). Penetration rates were greater across all treatments when both sperm and oocytes were co-incubated for 24h compared to 12h (P<0.001). There were no differences in penetration rates among the four donor stags used in the study.It was concluded that COEM sustains red deer sperm motility in vitro during the 24h observation period. Pre-incubating sperm on COEM does increase sperm penetration rates compared with heparin alone, but at a rate too low and variable to be used on a routine basis. Overall, the penetration rates were comparable to those previously reported for red deer even though differences in heparin concentration, fertilisation systems and stags were used.     

Experiences in deer sperm cryopreservation under practical conditions--a pilot study

The genetic potential of the red and fallow deer populations in Hungary is well known. Conserving the variability in this excellent genetic material for game preservation is one of our most important task. The aim of the present pilot study was to test the logistical steps of a sperm processing and storing system in which deer sperm can be stored at a level that meets quality standards accepted for domestic animals. Moreover, two different semen extenders, commercially used for freezing bull semen, were compared from the viewpoint of applicability to freeze fallow deer sperm. Sperm was collected from epididymes of eight red stags (Cervus elaphus hippelaphus) and six fallow bucks (Dama dama) during the rutting season. Red deer samples were washed in Triladyl extender, while fallow deer samples were split and processed in Triladyl or Bioxcell extender. In the samples, which had a shorter time interval between the death of the animal and the sperm collection, the percentage of viable spermatozoa with intact acrosome was typically higher.     

Kinetics of immune responses in deer mice experimentally infected with sin nombre virus

Deer mice are the principal reservoir hosts of Sin Nombre virus, the etiologic agent of most hantavirus cardiopulmonary syndrome cases in North America. Infection of deer mice results in persistence without conspicuous pathology, and most, if not all, infected mice remain infected for life, with periods of viral shedding. The kinetics of viral load, histopathology, virus distribution, and immune gene expression in deer mice were examined. Viral antigen was detected as early as 5 days postinfection and peaked on day 15 in the lungs, hearts, kidneys, and livers. Viral RNA levels varied substantially but peaked on day 15 in the lungs and heart, and antinucleocapsid IgG antibodies appeared in some animals on day 10, but a strong neutralizing antibody response failed to develop during the 20-day experiment. No clinical signs of disease were observed in any of the infected deer mice. Most genes were repressed on day 2, suggesting a typical early downregulation of gene expression often observed in viral infections. Several chemokine and cytokine genes were elevated, and markers of a T cell response occurred but then declined days later. Splenic transforming growth factor beta (TGF-β) expression was elevated early in infection, declined, and then was elevated again late in infection. Together, these data suggest that a subtle immune response that fails to clear the virus occurs in deer mice.     

Decay of sperm obtained from epididymes of wild ruminants depending on postmortem time

We have carried out a study on the effect of postmortem time (PT) in some characteristics of epididymal sperm salvaged from hunted Iberian red deer and roe deer. Testis were collected, identified, refrigerated down to 5 degrees C, and sent to our laboratory by the wardens of the hunting reserves. This way, samples were delivered at different times postmortem. Sperm were extracted from the cauda epididymis by means of cuts. Analyzed parameters were: osmolality, pH, motility-both subjectively and with CASA, HOS test reactivity, acrosomal status and viability (assessed with propidium iodide). Osmolality and pH rose with prolonged postmortem time, possibly due to tissue decomposition. Most sperm quality parameters negatively correlated with PT. Besides, when comparing PT classes (groups of 24 h for red deer and 30 h for roe deer), we could appreciate that motility was more affected by PT than other quality variables. Progressive motility was especially impaired. We also classified the samples in high, medium and low quality for each PT group (considering progressive motility, intact acrosomes and reactivity to the HOS test), and it was clear that after 2 days the number of high quality samples was testimonial, and after several days, we almost found only low quality samples. In conclusion, epididymal sperm from Iberian red deer and roe deer undergo a decrease of quality with PT, but it could stay acceptable within many hours postmortem. There are implications for wildlife conservation programs, as epididymal sperm is a good source of germplasm. If valuable animals die and it is not possible to process their sperm immediately, it may still be possible to obtain viable spermatozoa many hours later.     

Coexistence of white-footed mice and deer mice may be mediated by fluctuating environmental conditions

White-footed mice, Peromyscus leucopus noveboracensis, and deer mice, P. maniculatus nubiterrae, occur sympatically throughout much of the Appalachian Mountains of the eastern United States. Previous studies have shown that these two species are behaviorally and ecologically similar and do not partition food or microhabitat. In this paper I use a 14-year data set to demonstrate that the two species have differential population growth and survival rates in response to food abundance and season, which may mediate their coexistence. The ratio of white-footed mice to deer mice ranged from 0.5:1 to 6:1. During summer and times of tood abundance, white-footed mice gained a numerical advantage over deer mice in 10 of 14 years, whereas following winter and poor food production, deer mice had higher survival in 9 of 13 years. The major decline in white-foote mice, but not deer mice, was associated with poor mast (acorn) production in autumn. Differential survival of deer mice may be due to their physiological adaptations to cold temperature and efficient use of torpor during food shortage. Inter-year variance in food production and climatic conditions appear to change the competitive advantage of each species often enough to permit coexistence. Coexistence of these two ecologically similar species may be maintained by different physiological limitations in a fluctuating environment.     

Short-day enhancement of immune function is independent of steroid hormones in deer mice (Peromyscus maniculatus)

The effects of photoperiod and steroid hormones on immune function were assessed in male and female deer mice (Peromyscus maniculatus). In experiment 1, male deer mice were castrated, castrated and given testosterone replacement, or sham-operated. Half of each experimental group were subsequently housed in either long (LD 16:8) or short days (LD 8:16) for 10 weeks. Short-day deer mice underwent reproductive regression and displayed elevated lymphocyte proliferation in response to the T-cell mitogen concanavalin A, as compared to long-day mice. In experiment 2, female deer mice were ovariectomized, ovariectomized and given estrogen replacement, or sham-operated. Animals from each of these experimental groups were subsequently housed in either LD 16:8 or LD 8:16 for 10 weeks. Short-day deer mice underwent reproductive regression and displayed reduced serum estradiol concentrations and elevated lymphocyte proliferation in response to concanavalin A, as compared to long-day mice. Surgical manipulation had no effect on lymphocyte proliferation in either male or female deer mice. Neither photoperiod nor surgical manipulation affected serum corticosterone concentrations. These results confirm that both male and female deer mice housed in short days enhance immune function relative to long-day animals. Additionally, short-day elevation in splenocyte proliferation appears to be independent of the influence of steroid hormones in this species. Accepted: 17 April 1998     

Does small-perimeter fencing inhibit mule deer or pronghorn use of water developments?

Wildlife water development can be an important habitat management strategy in western North America for many species, including both pronghorn (Antilocapra americana) and mule deer (Odocoileus hemionus). In many areas, water developments are fenced (often with small-perimeter fencing) to exclude domestic livestock and feral horses. Small-perimeter exclosures could limit wild ungulate use of fenced water sources, as exclosures present a barrier pronghorn and mule deer must negotiate to gain access to fenced drinking water. To evaluate the hypothesis that exclosures limit wild ungulate access to water sources, we compared use (photo counts) of fenced versus unfenced water sources for both pronghorn and mule deer between June and October 2002–2008 in western Utah. We used model selection to identify an adequate distribution and best approximating model. We selected a zero-inflated negative binomial distribution for both pronghorn and mule deer photo counts. Both pronghorn and mule deer photo counts were positively associated with sampling time and average daily maximum temperature in top models. A fence effect was present in top models for both pronghorn and mule deer, but mule deer response to small-perimeter fencing was much more pronounced than pronghorn response. For mule deer, we estimated that presence of a fence around water developments reduced photo counts by a factor of 0.25. We suggest eliminating fencing of water developments whenever possible or fencing a big enough area around water sources to avoid inhibiting mule deer. More generally, our results provide additional evidence that water development design and placement influence wildlife use. Failure to account for species-specific preferences will limit effectiveness of management actions and could compromise research results. © 2011 The Wildlife Society.     

Season effect on genitalia and epididymal sperm from Iberian red deer, roe deer and Cantabrian chamois

Seasonality deeply affects the physiology and behavior of many species, and must be taken into account when biological resource banks (BRBs) are established. We have studied the effect of seasonality on many reproductive parameters of free-ranging Iberian red deer, roe deer and Cantabrian chamois, living in Spain. Testicles from hunted animals were collected and sent to our laboratory at different times during the year. We recorded the weight and volume of testis, the weight of the epididymis and its separate parts (caput, corpus, and cauda), the weight of the sperm sample collected from the cauda epididymis, and several sperm parameters (sperm concentration, spermatozoa recovered, motility, HOS test reactivity, acrosomal status, and viability). We studied the data according to several periods, defined accordingly to each species. For red deer, we defined rut (mid-September to mid-October), post-rut (mid-October to mid-December), and non-breeding season (February). For roe deer, they were pre-rut (June), rut (July), post-rut (first fortnight of August), and non-breeding season (September). For chamois: non-breeding season (June to mid-September) and breeding season (October-November). The rut/breeding season yielded significantly higher numbers for almost all parameters. However, in the case of red deer, sperm quality was higher in the post-rut. For roe deer, testicular weight was similar in the pre-rut and in the rut, and sperm quality did not differ significantly between these two periods, although we noticed higher values in the rut. In the case of chamois, sperm quality did not differ significantly from the breeding season, but data distribution suggested that in the non-breeding season there are less males with sperm of good quality. On the whole, we find these results of interest for BRB planning. The best season to collect sperm in this species would be the breeding season. However, post-rut in red deer, pre-rut in roe deer, and non-breeding season in chamois could be used too, because of the acceptable sperm quality, despite the lower quantity salvaged. More in-depth research needs to be carried out on the quality of sperm salvaged at different times of the year in order to confirm these findings.     

The influence of artificial photoperiod on the growth,appetite and reproductive status of male red deer and sheep

Young male red deer and Suffolk X (Finn X Dorset) sheep were kept on an artificial photoperiod such that two cycles of daylength occurred during one calendar year. They were penned separately, fed to appetite, weighed weekly and measured tri-weekly.Both species showed two cycles of intake, growth and gonadal activity in response to the daylength when only one would have been shown on natural photoperiod, although in the sheep these cycles were of lower amplitude than in the deer. The deer grew two sets of antlers during the study. A lag of some 3–4 months occurred between an event such as peak food intake and the time it would have been expected to occur relative to the daylength cycle. It is considered that although daylength controls these cycles, there is an endogenous rhythm which photoperiod cannot completely suppress.     

Differential resource allocation in deer mice exposed to sin nombre virus

The resource allocation hypothesis predicts that reproductive activity suppresses immunocompetence; however, this has never been tested in an endemic disease system with free-ranging mammals. We tested the resource allocation hypothesis in wild deer mice (Peromyscus maniculatus) with natural exposure to Sin Nombre Virus (SNV). Immunocompetence was estimated from the extent of swelling elicited after deer mice were injected with phytohemagglutinin (PHA); swelling is positively correlated with immunocompetence. After livetrapping deer mice, we determined their reproductive state and SNV infection status. Males were more likely to be seropositive for SNV than females (37% vs. 25%) and exhibited 10% less swelling after PHA injection. The swelling response of females differed with both infection status and reproductive condition. There was also a significant infection status by reproductive condition interaction: non-reproductive, seropositive females experienced the least amount of swelling, whereas females in all other categories experienced significantly greater swelling. The swelling response of males differed with both SNV infection status and reproductive condition, but there was no significant infection status by reproductive condition interaction. Seronegative males elicited greater swelling than seropositive males regardless of reproductive status. In contrast to the resource allocation hypothesis, these results do not indicate that reproductive activity suppresses immunocompetence of deer mice but rather suggest that chronic SNV infection reduces immunocompetence. Sex-based differences in swelling indicate that SNV modulates the immune system of female deer mice differently than it does that of males, particularly during reproduction. We propose that differences in resource allocation between males and females could result from inherent sex-based differences in parental investment.     

Responses to lactation and cold exposure by deer mice (Peromyscus maniculatus)

Recently, much interest has been expressed in understanding how animals use phenotypic plasticity of tissue size and function to meet increased metabolic demands. We set out to learn (i) whether female deer mice (Peromyscus maniculatus) given lactation (two to seven pups per litter), cold (5 degrees C), or cold plus lactation as energy demands display phenotypic plasticity in organ size and function; (ii) whether that plasticity is similar to laboratory mice given the same demands; and (iii) whether lactational performance in deer mice is derived from limits on central or peripheral organs. We found that deer mice responded to lactation by increasing digestible food intake and increasing the masses of the stomach, small intestine, cecum and liver, and the length of the small intestine. Heart mass was lower in lactating than in nonlactating mice. Cold exposure also caused increases in digestible food intake and increases in the masses of the small intestine, kidney, and heart. We conclude that deer mice display organ tissue plasticity in response to both lactation and cold exposure in a similar manner to laboratory mice. We also conclude that deer mice are not limited by central processing organs because they are able to increase digestive organ size continuously with increased energetic demands.     

Seasonal acclimation of prairie deer mice

Prairie deer mice responded to long nights by reducing their metabolic rates, core temperatures, thermal conductances and incremental metabolic responses to cold stimulus, while increasing their capacities for nonshivering thermogenesis. Some winter animals spontaneously entered daily torpor in the mornings and thereby further reduced their metabolic rates and core temperatures. Provision of exogenous melatonin (by subdermal implants) mimiced short photoperiod effects on metabolic rates and core temperatures of wild-caught, laboratory maintained animals. Provision of supplemental dietary tryptophan to laboratory animals conditioned to natural light cycles mimiced metabolic effects of long nights in summer animals, and further reduced metabolic rates of winter mice, but did not affect their core temperature levels. Newly caught, laboratory maintained deer mice responded to natural seasonal clues of shortphotoperiod and increased dietary tryptophan by reducing their resting energy requirements through both lower metabolic and lower core temperature levels. Short photoperiod and seasonal change also promoted gonadal involution, and resulted in more socially tolerant huddling by mice with reduced core temperature. Reduced 24-hour LH excretion rates were also observed in winter animals which were exposed to seasonal light cycles at warm (25°C) room temperatures. We propose that seasonal acclimatization involves pineal effects on sex hormone-influenced social behaviors and on resting metabolism. These effects serve to conserve resting energy expenditure and promote hypothermic insulation by wild prairie deer mice.     

Differential reproductive response to short photoperiod in deer mice: role of melatonin

Summary Inhibitory photoperiod differentially effects reproduction in deer mice (Peromyscus maniculatus nebrascensis). Pituitary-testicular function is arrested in about one-third of short-day exposed males (reproductively responsive mice), while an equal number remain fertile (reproductively nonresponsive mice). Both phenotypes are found in natural populations and their disparate reproductive responses have a genetic basis. To assess whether this difference is attributable to a prepineal/pineal or post-pineal mechanism, we compared spermatogenic responses of known and unknown phenotype to exogenous melatonin. Melatonin significantly reduced mean sperm number in long-day housed mice of unknown phenotype. But, individual responses ranged from azoospermia to normal spermatogenesis, and this range was not significantly different from that previously recorded for short-day exposed mice. Reproductively nonresponsive males were unaffected by melatonin administration when housed under long or short daylength. In contrast, melatonin significantly suppressed sperm production in reproductively responsive males housed under long photoperiod, but had no additional suppressive effect in short-day housed mice with regressed testes. These data demonstrate that melatonin is only effective in eliciting testicular regression in reproductively responsive males. Taken together, these results suggest that differential testicular response to photoperiod are caused by a post-pineal mechanism.Abbreviations LD long day - SD short day - 16L:8D 16 h light, 8 h dark - 8L:16D 8 h light, 16 h dark     

Penetration of the zona-free or intact eggs by foreign spermatozoa and the fertilization of deer mouse eggs in vitro

Zona-free eggs were introduced to fresh or preincubated sperm suspensions and the penetration of eggs by foreign spermatozoa was examined, as evidenced by enlargement of the sperm head and formation of the male pronucleus. It was found that zona-free hamster eggs can be penetrated by guinea-pig, deer mouse and rabbit spermatozoa but zona-free rat, mouse and rabbit eggs cannot be penetrated by guinea-pig spermatozoa. Furthermore, zona-free rat and mouse eggs cannot be penetrated by spermatozoa from two species of deer mice and the Mongolian gerbil. The zona pellucida of a few intact rat eggs can be penetrated by mouse (6%) and by P. leucopus spermatozoa (14%) but enlargement of the sperm head and formation of pronuclei were observed in the former but not in the latter. It seems that (1) sperm capacitation is required for the penetration of zona-free eggs, (2) the attachment of foreign spermatozoa to eggs may indicate their potential ability of penetration in some cases, (3) there is a certain affinity between the vitellus of one species and spermatozoa from another species, (4) the block to the entry of foreign spermatozoa is not only in the zona pellucida but also in the vitelline membrane, (5) zona-free hamster eggs can be penetrated by spermatozoa of six species, (6) mouse spermatozoa can penetrate zona-free eggs of three species, and (7) fertilization of intact P. maniculatus eggs can be achieved in vitro.     

Phenotypic variation in seasonal adjustments of testis size, body weight, and food intake in deer mice: role of pineal function and ambient temperature

We investigated pineal function as well as reproductive and energetic characteristics in male deer mice (Peromyscus maniculatus) that differentially respond to short photoperiod with full, partial or no gonadal regression. In mice at both high (23 °C) and low temperature (1 °C), these phenotypic differences in reproductive responses to short days were not reflected by differences in urinary excretion of 6-sulphatoxy-melatonin, the main metabolite of pineal melatonin. Neither duration nor amplitude or phase-angle of nocturnal peaks in 6-sulphatoxymelatonin significantly differed between reproductive phenotypes at either temperature. Differences in testis size were, however, associated with different energy requirements. In gonadally regressed males only, food intake and body weight were significantly (P < 0.01) reduced by up to 29% and 13% respectively. Chronic cold exposure (5 °C) had no effect on the proportion of males undergoing testicular regression under short days, but caused a general elevation in body weights among all mice (P < 0.05). Phenotypic differences in body weight and food intake were maintained in the cold. Together, these results suggest that within-population variation of reproductive responses in male deer mice is based on post-pineal differences in the regulation of gonadal function, and that phenotypic characteristics in reproductive and energetic responses to short days are largely unaffected by ambient temperature. Accepted: 2 October 1995     

Effects of morphine on electrically evoked contractions of the vas deferens in two congeneric rodent species differing in sperm competition intensity.

An early prediction of sperm competition theory was that males should adjust the number of sperm they deliver according to the risk of double mating and this has received empirical support in recent years. It has been suggested that adaptive regulation of sperm delivery in mammals may depend on changes in vas deferens contractility. In laboratory mice, the vas deferens is sensitive to opioid agonists and the secretion of endogenous opioid peptides can be affected by social interactions that may be predictive of sperm competition risk. The present experiment was conducted to determine whether morphine, an opioid agonist (at the mu-receptor), has different effects on electrically evoked contractions of the isolated vas deferens in two congeneric rodent species differing in sperm competition intensity. Morphine inhibited contractions of the vas deferens in the non-monogamous deer mouse (Peromyscus maniculatus) but not the monogamous California mouse (Peromyscus californicus). This implies that the vas deferens of P. maniculatus possesses functional mu-receptors and, thus, should be able to respond to changes in the circulating levels of endogenous agonists whose secretion can be affected by social interactions predictive of sperm competition risk.     

Screening Evaluation of the Ecological Risks to Terrestrial Wildlife Associated with a Coal Ash Disposal Site

Between 1955 and 1989, coal ash was deposited within an impounded watershed on the U.S. Department of Energy's Oak Ridge Reservation in Tennessee, creating the 3.6?ha Filled Coal Ash Pond (FCAP). The site has subsequently become vegetated wildlife habitat. To evaluate risks that metals in ash may pose to wildlife; ash, surface water, small mammal, and vegetation samples were collected and metal residues were determined. Metal concentrations, As and Se in particular, were elevated in ash, surface water, plant foliage, and small mammals relative to reference materials. Estimates of metal exposures were calculated for short-tailed shrews, white-footed mice, white-tailed deer, red fox, and red-tailed hawks. While shrews and mice were assumed to reside exclusively at and receive 100% exposure from the site, exposure experienced by deer, fox, and hawks was assumed to be proportional to the size of the site relative to their home range. Because deer had been observed to consume ash, presumably for its high sodium content, exposure experienced by deer consuming ash to meet sodium requirements was also estimated. Exposure estimates were compared to body-size adjusted toxicity data for each metal. These comparisons suggest that metals at the site may be detrimental to reproduction and survivorship of mice, shrews, and deer consuming ash for sodium; fox and hawks do not appear to be at risk