Synergistic effects of predation and parasites on the overwinter survival of root voles.

Predators and parasites have been important extrinsic factors influencing the fluctuation of small mammal populations. They can have non-additive effects on a shared group of preys or hosts, which can have important consequences for population dynamics. However, experimental studies incorporating the interactions between predation and parasites are scarce in small mammal populations. Here we systematically examined the synergistic effects of predators and coccidian parasites interaction on overwinter survival and likely mechanisms underlying the synergistic effects in the root vole (Microtus oeconomus). Our aim was to test the general hypothesis that predators and coccidia interact synergistically to decrease overwinter survival of root voles through mediating vole's physiological traits and body conditions. We carried out a factorial experimental design, by which we manipulated the predator exclusion in combination with the parasitic removal in enclosures, and then measured fecal corticosterone metabolite (FCM) levels, immunocompetence, and body conditions in captured animals via repeated live trapping. We found a strong negative synergistic effect of predators and coccidia on survival. Importantly, we found that predators increased both the prevalence and intensity of coccidian infection in voles through immune suppression induced by predation stress, while increased coccidian infection reduced plasma protein and hematocrit level of voles, which may impair anti-predator ability of voles and lead to an increase in predation. Our finding showed when voles are exposed to both predation risk and infection, their synergistic effects greatly reduce overwinter survival and population density. This may be an important mechanism influencing population dynamics in small mammals.

Five new species of Eimeria Schneider, 1875 from the endangered Tibetan antelope Pantholops hodgsonii (Abel) (Artiodactyla: Bovidae: Caprinae) in the Hoh Xil Nature Reserve Area of Qinghai Province, China.

We examined faeces of 76 endangered Tibetan antelopes Pantholops hodgsonii (Abel) in May 2017, from the Hoh Xil Nature Reserve, Qinghai Province, China, and found 62/76 (82%) discharging oöcysts representing five new species of Eimeria Schneider, 1875. Oöcysts of Eimeria pantholopensis n. sp., found in 54/76 (71%) chiru, are subspheroidal/ellipsoidal, 15-22 × 12-19 (18.6 × 16.1) µm, with a length/width (L/W) ratio of 1.0-1.3 (1.2); micropyle cap and 1-3 polar granules are present, but oöcyst residuum is absent. Sporocysts are ovoidal, 7-11 × 4-6 (9.2 × 5.3) µm, with a L/W ratio of 1.6-2.0 (1.7); Stieda body and sporocyst residuum of small, scattered granules are present; each sporozoite contains 2 refractile bodies. Oöcysts of Eimeria wudaoliangensis n. sp. found in 52/76 (68%) chiru, are pyriform, 21-29 × 17-21 (24.9 × 19.0) µm, with a L/W ratio of 1.1-1.5 (1.3); micropyle, micropyle cap and 1-4 polar granules are present, but oöcyst residuum is absent. Sporocysts are ovoidal, 9-13 × 5-8 (11.7 × 6.7) µm, with a L/W ratio of 1.4-2.7 (1.7); Stieda body and sporocyst residuum of disbursed granules are present; sporozoites have a single large refractile body. Oöcysts of Eimeria hodgsonii n. sp. found in 20/76 (26%) chiru, are elongate-ellipsoidal, 25-32 × 18-21 (28.9 × 19.8) µm, with a L/W ratio of 1.2-1.7 (1.5); micropyle, micropyle cap and 1-3 polar granules are present, but oöcyst residuum is absent. Sporocysts are ovoidal, 11-14 × 6-7 (12.3 × 6.8) µm, with a L/W ratio of 1.7-2.1 (1.8); Stieda body and sporocyst residuum as group of large granules lying along the interface between intertwined sporozoites are present; sporozoites have 2 refractile bodies. Oöcysts of Eimeria schalleri n. sp. found in 49/76 (64.5%) chiru, are ellipsoidal, 26-36 × 19-25 (30.4 × 23.2) µm, with a L/W ratio of 1.2-1.5 (1.3); micropyle with micropyle cap and polar granules appearing as many diffuse tiny bodies are present, but oöcyst residuum is absent. Sporocysts are ovoidal, 12-16 × 7-9 (14.2 × 7.8) µm, with a L/W ratio of 1.6-2.1 (1.8); Stieda body and sporocyst residuum are present, the latter as a group of small dispersed granules between intertwined sporozoites; sporozoites with 2 refractile bodies. Oöcysts of Eimeria sui n. sp. found in 4/76 (5%) chiru, are ovoidal, 32-38 × 26-30 (36.6 × 28.6) µm, with a L/W ratio of 1.0-1.4 (1.3); micropyle and micropyle cap and 1-3 polar granules are present, but oöcyst residuum is absent. Sporocysts are ovoidal, 15-18 × 8-10 (16.7 × 8.9) µm, with a L/W ratio of 1.7-2.1 (1.9); Stieda body and sporocyst residuum are present, the latter as a group of dispersed small granules; sporozoites with 2 refractile bodies. Five of 62 faecal samples in which oöcysts were detected (8%) had a single species infection, 13 of 62 (21%) had two species, 28 of 62 (45%) had three species and 16 of 62 (26%) had four species.

The synergistic effect of density stress during the maternal period and adulthood on immune traits of root vole (Microtus oeconomus) individuals-a field experiment.

The literature reveals that stress in early life or adulthood can influence immune function. As most studies on this are from the laboratory, there is a need for replicated studies in wild animals. This study aims to examine the effects of density stress during the maternal period and adulthood on immune traits of root vole (Microtus oeconomus) individuals. Four replicated high- and low-density parental populations were established, from which we obtained offspring and assigned each into four enclosures, two for each of the two density treatments used in establishing parental populations. The F1 offspring fecal corticosterone metabolite response to acute immobilization stress, anti-keyhole limpet hemocyanin immunoglobulin G (anti-KLH IgG) level, phytohemagglutinin (PHA)-delayed hypersensitivity and hematology at the end of the first breeding season, and prevalence and intensity of coccidial infection throughout the two breeding seasons, were tested. Density-induced maternally stressed offspring had delayed responses to acute immobilization stress. Density-stressed offspring as adults had reduced anti-KLH IgG levels and PHA responses, and the effects further deteriorated in maternally stressed offspring, leading to higher coccidial infection in the first breeding season than in the second. No correlations were found between immune traits or coccidial infection and survival over winter. These findings indicated that the combined density stresses during the maternal period and adulthood exhibited negative synergistic effects on immune traits. The synergistic effects lead to higher coccidial infection; however, this consequently reduced the risk of subsequent infection. The increased coccidial infection mediated by the synergistic effects may have an adaptive value in the context of the environment.

Maternal effects and population regulation: maternal density-induced reproduction suppression impairs offspring capacity in response to immediate environment in root voles Microtus oeconomus.

The hypothesis that maternal effects act as an adaptive bridge in translating maternal environments into offspring phenotypes, and thereby affecting population dynamics has not been studied in the well-controlled fields. In this study, the effects of maternal population density on offspring stress axis, reproduction and population dynamics were studied in root voles (Microtus oeconomus). Parental enclosures for breeding offspring were established by introducing six adults per sex into each of 4 (low density) and 30 adults per sex into each of another 4 (high density) enclosures. Live-trapping started 2 weeks after. Offspring captured at age of 20-30 days were removed to the laboratory, housed under laboratory conditions until puberty, and subsequently used to establish offspring populations in these same enclosures, after parental populations had been removed. [Correction added on 8 January 2015 after first online publication: '10-20 days' has been changed to '20-30 days.'] Offspring from each of the two parental sources were assigned into four enclosures with two for each of the two density treatments used in establishing parental populations (referred to as LL and LH for maternally unstressed offspring, assigned in low and high density, and HL and HH for maternally stressed offspring, assigned in low and high density). Faecal corticosterone metabolites (FCM) levels, offspring reproduction traits and population dynamics were tested following repeated live-trapping over two seasons. Differential fluctuations in population size were observed between maternally density-stressed and density-unstressed offspring. Populations in LL and LH groups changed significantly in responding to initial density and reached the similar levels at beginning of the second trapping season. Populations in HL and HH groups, however, were remained relatively steady, and in HL group, the low population size was sustained until end of experiment. Maternal density stress was associated with FCM elevations, reproduction suppression and body mass decrease at sexual maturity in offspring. The FCM elevations and reproduction suppression were independent of offspring population density and correlated with decreased offspring quality. These findings indicate that intrinsic state alterations induced by maternal stress impair offspring capacity in response to immediate environment, and these alterations are likely mediated by maternal stress system. The maladaptive reproduction suppression seen in HL group suggests intrinsic population density as one of ecological factors generating delayed density-dependent effects.

Four new coccidia (Apicomplexa: Eimeriidae) from the Plateau zokor, Myospalax baileyi Thomas (Rodentia: Myospalacinae), a subterranean rodent from Haibei area, Qinghai Province, China.

Thirty-eight faecal samples from the Plateau zokor, Myospalax baileyi Thomas, collected in the Haibei Area, Qinghai Province, China, were examined for the presence of coccidia (Apicomplexa: Eimeriidae). Seventeen of 38 faecal samples (44.7%) were found to contain coccidian oöcysts representing four new species of Eimeria Schneider, 1875, and four of 17 (23.5%) infected zokors were concurrently infected with two or three of these eimerian species. The sporulated oöcysts of Eimeria myospalacensis n. sp. are ovoidal, 9.5-17.0 × 8.0-13.0 (mean 13.0 × 10.4) µm; a polar granule is present, oöcyst residuum is absent; sporocysts are ovoidal, 4.5-7.5 × 3.0-5.0 (mean 6.3 × 4.2) µm and have both a Stieda body and residuum. Oöcysts of Eimeria fani n. sp. are ellipsoidal to cylindroidal, 12.5-16.0 × 8.0-11.0 (mean 14.6 × 9.9) µm; a polar granule is present, but micropyle and residuum are lacking; sporocysts are ovoidal, 4.5-7.5 × 3.0-5.3 (mean 6.7 × 4.4) µm; a residuum and a Steida body are present. Oöcysts of Eimeria baileyii n. sp. are ellipsoidal, 15.0-23.0 × 12.0-18.0 (mean 18.2 × 13.7) µm; a polar granule is present but oöcyst residuum is absent; sporocysts are ovoidal, 8.0-11.0 × 5.0-7.0 (mean 9.5 × 5.9) µm and have both a Stieda body and residuum. Oöcysts of Eimeria menyuanensis n. sp. are ovoidal, 12.5-21.0 × 11.0-18.0 (mean 17.1 × 14.6) µm, with a distinct micropyle c.2.5 µm wide; a polar granule is present but a residuum is absent; sporocysts are ovoidal, 8.0-12.0 × 5.0-7.0 (mean 10.2 × 6.4) µm, and have both a Stieda body and residuum.

Eimeria spp. (Apicomplexa: Eimeriidae) from the Plateau pika, Ochotona curzoniae, from Haibei Area, Qinghai Province, China, with the description of two new species.

Fifty-two fecal samples from the Plateau pika, Ochotona curzoniae, collected in the Haibei Area, Qinghai Province, China, were examined for the presence of coccidia (Apicomplexa: Eimeriidae). Five distinct morphotypes, all Eimeria species, were distinguished based on the structure of their sporulated oocysts. Three of these included Eimeria banffensis, Eimeria calentinei, and Eimeria cryptobarretti, all of which have been described previously from other Ochotona species. We also studied 2 morphotypes that we feel have sufficient qualitative and quantitative characters to distinguish them from all previously described species; herein, we identify them as putative new species. Eimeria qinghaiensis n.sp. was found in 18/52 (35%) O. curzoniae. It has ovoidal oocysts with a 3-layered wall, with a rough outermost layer and a micropyle, approximately 9 microm wide. Sporulated oocysts are 37.2 x 27.2 (34-41 x 24-32) microm; 1 polar granule is present, but an oocyst residuum is absent. Sporocysts are ovoidal, 16.6 x 9.8 (14-19 x 9-11) microm with a Stieda body; sporocyst residuum and sporozoites have 2 refractile bodies. Eimeria haibeiensis n. sp. was found in 21/52 (40%) pikas. It has ellipsoidal to ovoidal oocysts, with a 2-layered smooth wall and a micropyle, 3.9 microm wide. Oocysts are 22.2 x 16.2 (20-24 x 15-18) microm; polar granule and oocyst residuum are both absent. Sporocysts are ovoidal, 11.6 x 6.6 (10-13 x 5-7) microm, with a Stieda body; sporocyst residuum and sporozoites each have 2 refractile bodies, 1 at each end. The 5 eimerian species we discovered in O. curzoniae in China all represent new host and locality records.