Large manipulative experiments reveal complex effects of food supplementation on population dynamics of Brandt's voles

Although food supplementation is well known to increase population density,there is still debate on the causative effects of food supplementation on reproduction,survival,and immigration.Large manipulative experiments,which exclude any confounding effects of dispersal and predation,are essential for clarifying the debate.In this study,we investigated the effects of food supplementation on Brandt's vole population dynamics and plant community in eight large enclosures(0.48 ha each) from2010 to 2014.Food supplementation showed significant positive effects on population density due to increases in recruitment;however,it showed a complex effect on survival of voles:positive in non-breeding seasons,but negative in breeding seasons.In addition,food supplementation increased the quality of plants(as reflected by increased crude protein content),but decreased the quantity of less preferred plants in experimental enclosures.Thus,food seems to have direct positive effects on small rodents through improvement of food supply and indirect negative effects through food-induced density-dependent effects,and may have long-term effects on rodents through altering plant community composition and abundance.

Effects of maternal stress induced by predator odors during gestation on behavioral and physiological responses of offspring in Brandt’s vole(Lasiopodomys brandtii)

Maternal effects play a crucial role in regulating populations of small mammals and anti-predator behaviors of offspring.The present study investigated the effects of maternal stress induced by exposure to predator odors during gestation on the behavioral and physiological responses of offspring in Brandt’s vole(Lasiopodomys brandtii).Effects included changes in growth,behaviors,hormone levels in serum,and fosB/ΔfosB mRNA and FosB/ΔFosB protein expression in the hypothalamus.Our results showed that when pregnant voles were exposed to cat and rabbit urine odors for 18 days(1 h/day),the weight of the female offspring decreased;however,the thymus and ovary indices increased,compared with the control group.Male offspring of voles exposed to cat odor spent more time exploring and foraging,and showed a decrease in corticosterone(CORT)compared with voles in the control group.Both fosB/ΔfosB mRNA and FosB/ΔFosB protein expressions were downregulated in the hypothalamus of male offspring in the cat odor-exposed group compared to that in offspring in the control group.However,the mRNA levels of fosB/ΔfosB in the hypothalamus of female offspring did not decrease in response to cat urine odor.Our findings suggested that maternal stress induced by predator odors during gestation restrained the growth of female offspring and increased the duration of exploring and foraging behaviors of male offspring by regulating the HPA axis,which,in turn,reduced the sensitivity of offspring to unfamiliar environments and increased their probability of becoming prey.

Characteristics of the Achnatherum splendens community along the Qinghai-Tibet Railway, China

The Achnatherum splendens community is an important type of warm steppe vegetation which plays a very important role in environmental protection in the area along the Qinghai-Tibet Railway.In order to understand its dynamic features,the characteristics of the A.splendens community,such as spatial distribution pattern,species richness and biomass,were examined near Haiyan County,Qinghai Province.Results showed that the A.splendens community consisted of two types of mosaic patches,the microaggregation dominated by A.splendens and the microaggregation dominated by Stipa sp.The number and size of the two patches showed an interesting distribution pattern.The A.splendens patch decreased with increasing distance away from the railway,while species diversity increased.The total coverage of A.splendens was significantly higher than that of Stipa sp.The number and size of patches may indicate the degradation of the A.splendens community,which could be accelerated by human activities.Based on the characteristics and status quo of the A.splendens community,we suggest that some measures be taken to control human activities and rodents to conserve the A.splendens community.

Antibacterial properties of extracts of Solidago canadensis and their potential use as dietary supplements in red swamp crayfish(Procambarus clarkii)

Canadian goldenrod(Solidago canadensis)is one of the most destructive invasive weeds in Southeastern China.To evaluate its potential application as dietary supplement in red swamp crayfish(Procambarus clarkii),the antibacterial properties of aqueous and ethanol extracts of this plant against three major pathogenic bacteria in crayfish aquaculture were examined.Inhibition zone tests and determination of minimum inhibitory concentration revealed that the extracts had lower antibacterial activity than extracts from two traditional medicinal plants that possess antibacterial properties,garlic(Allium sativum)and cortex phellodendri(Phellodendron chinense).However,they did exhibit greater antibacterial effects than extracts from another widely used medicinal plant,Sophora flavescens,and an aquatic weed,Alternanthera philoxeroides.Aqueous extracts of Canadian goldenrod gave greater inhibition than the ethanol extracts.Crayfish fed a diet with 2%these aqueous extracts exhibited significantly higher enzyme activity of alkaline phosphatase,catalase and phenoloxidase(P<0.05).Based on the results of this study,we conclude that aqueous extracts of Canadian goldenrod are highly promising for the development of new dietary supplement for use in crayfish aquaculture.