Male reproductive success in free-ranging feral horses

In the social organization of feral horses, adult males compete to monopolize groups or bands of females, sometimes called harems. Alternative male strategies are to remain alone or with other bachelors or, less commonly, to accept subordinate status within a harem. The hypothesis that dominant harem stallion status confers a reproductive advantage was tested in free-ranging feral horses. The presence of foals in harems headed by vasectomized (VSX) versus intact stallions was used to assess the ability of these stallions to control reproduction in their harems. Of harems headed by VSX stallions, 17 and 33% contained foals during years 2 and 3 post-treatment, respectively. In contrast, 86 and 80% of harems headed by non-VSX stallions contained foals in those years. Acquisition of pregnant mares appeared more likely than sneak copulations by bachelor stallions to account for foals in harems with a single stallion. However, most foals were born into harems that included a subordinate stallion, an occurrence that was undoubtedly exacerbated by the extended breeding season resulting from the sterility of the harem stallion. Thus, in comparing alternative reproductive tactics, bachelors appeared less successful than subordinate stallions within a harem. However, the highest reproductive success was achieved by the harem stallion, further demonstrating that alternative tactics are not equally profitable. Received: 13 July 1999 / Received in revised form: 24 July 1999 / Accepted: 24 July 1999     

DDT polluted meltwater affects reproduction in the mussel Dreissena polymorpha

The zebra mussel Dreissena polymorpha was used to follow the recently reported DDT pollution of Lake Iseo (N. Italy). Histopathological analyses were performed on mussels sampled from March 2005 to April 2006, when high DDT levels were found, and results were compared to those from mussels sampled in 2001/2002, before the pollution event. During the 2005/2006 reproductive season, the first male gamete release happened one month later than the onset of spawning in females who showed a high number of specimens with degenerating oocytes, despite a regular pattern of gametogenesis. These results indicated a disrupting action of DDT on the mechanisms involved in sperm release, and a disturbance in the gametogenic phases of the ovary. Pathological pictures in the digestive gland of many mussels from both 2001/2002 and 2005/2006 have also been observed, but DDT pollution is unable to explain the presence of pathological fields in mussels during 2001/2002, for which a previously reported contamination seems to be the main cause. A possible role of DDT in skewing the sex ratio towards a predominance of females was also discussed, considering the high number of females sampled in 2005/2006.     

Reproductive toxicity assessment of surface water of the Tai section of the Yangtze River, China by in vitro bioassays coupled with chemical analysis

Reproductive toxicity of organic extracts of the surface water from the Tai section of the Yangtze River was assessed by in vitro cytotoxity assays and selected persistent organic pollutants including PCBs, OCPs and PAHs were quantified by instrumental analysis. Eleven of the US EPA priority PAHs were detected. Individual PAHs were found to range from 0.7 to 20 ng/L. Concentrations of BaP did not exceed the national drinking water source quality standard of China. However, a 286-fold concentrated organic extract induced significant reproductive toxicity in adult male rats. The morphology of cells, MTT assay and LDH release assay were all affected by exposure to the organic extracts of water. The results of the reproductive toxicity indicated that PAHs posed the greatest risk of the chemicals studied. The compounds present in the water could be bioconcentrated and result in adverse effects.     

Integration of Land-Sharing and Land-Sparing Conservation Strategies Through Regional Networking: The Mesoamerican Biological Corridor as a Lifeline for Carnivores in El Salvador

Nations with little remaining natural habitat and small extent are challenged when trying to achieve biodiversity targets. We show that the Central American nation of El Salvador cannot viably sustain populations of 87 % of its extant carnivores, especially in the case of large-bodied species with low population densities. Current land-sparing strategies will not suffice; therefore we propose that land-sharing strategies be implemented in tandem with protected areas to expand current conservation efforts via new regional networks. In Central America such a network can be established by linking international protected area systems in a way that implements the existing vision for the Mesoamerican Biological Corridor. Specifically, we propose a re-envisioning of the Mesoamerican Biological Corridor in which land-sharing practices are adopted throughout the agricultural matrix while ensuring formal protection of the remaining natural habitat. Such an integration of land-sparing and land-sharing could result in the creation of an effective network of protected areas, thereby increasing the probability of safeguarding species with populations that overlap national borders.     

The use of incubation behavior to adjust avian reproductive costs after egg laying

Reproduction in birds requires the input of time and energy during discrete breeding phases leading to investment trade-offs between laying date, clutch size, body mass, and incubation constancy. We investigated costs during incubation by experimentally enlarging 25 clutches of white-tailed ptarmigan Lagopus leucurus. The experiment was conducted in 2 years, one with harsh weather that forced a natural delay in reproduction. When forced to delay egg-laying, females began incubation with poorer body condition and foraged more during incubation. Rates of mass loss during incubation were not affected by clutch enlargement, and did not differ between harsh and benign years; however, females that were heavier at the start of incubation lost more mass than lighter females. Clutch-enlarged females had reduced nest attendance compared to control birds in both years and incubation periods increased by up to 2 days relative to controls. In the harsh year, there was a trend for clutch-enlarged females to have lower nest success, but there was no effect on overwinter survival. Different behavioral responses by females in the 2 years showed that incubation costs may depend on other factors such as female quality, food supply, or weather conditions. Incubation is a dynamic period during which birds may adjust energy balances by varying body condition and food intake. Received: 28 March 2000 / Received in revised form: 18 August 2000 / Accepted: 2 July 2000     

Effects of estrogen exposure in mussels, Mytilus edulis, at different stages of gametogenesis

Mytilus edulis were exposed to 17β-estradiol (E2) and the synthetic estrogens ethinyl estradiol (EE2) and estradiol benzoate (EB) for 10 days. Two exposures were performed to determine their effect on vitellogenin (VTG) and estrogen receptor 2 (ER2) mRNA expression at different stages of the reproductive cycle. Significant natural variation was not observed in VTG mRNA expression, though ER2 mRNA expression displayed significantly lower values during January, February and July compared with other times of the year. A significant increase in VTG and ER2 mRNA expression was observed in mussels exposed to estrogens at the early stage of gametogenesis. In contrast, mature mussels displayed no statistically significant change in the VTG or ER2 mRNA expression. The data presented suggests that the reproductive physiology of molluscs, in terms of VTG and ER2 mRNA expression, may be susceptible to damage by environmental estrogens at certain points in their gametogenesis process.     

科学谋划“十四五”国家生态环境监测网络建设

党的十八大以来,党中央、国务院高度重视环境监测工作,将生态环境监测纳入生态文明改革的大局统筹推进,取得了前所未有的显著成效。然而与建设美丽中国的新要求及国际先进水平相比, 中国的生态环境监测网络仍存在差距。笔者深入研究了当前和今后一个时期国家生态环境监测网络发展方向 ,并提出相应建议。针对空气、地表水、土壤、生态、声等要素的国家生态环境监测网络,分别提出网络布局及点位优化的原则,强调应通过理顺国家生态环境监测网运行机制、建立部门协作机制、健全生态环境监测法规标准体系、加强监测新技术研究及成果转化、强化监测装备自主研发等方式加强生态环境监测网络相关保障。     

医用电气设备的环境试验

国家标准GB9706.1-2007《医用电气设备第1部分：安全通用要求》中10.1和10.2明确规定了医用电气设备的运输和储存、运行等环境条件,具体试验方法则依据国家标准GB/T14710-93《医用电气设备环境要求及试验方法》。     

关于生态文明建设的三个难点问题简述

学界对生态文明与其他文明的关系、生态文明是否是独立的文明形态,看法不大统一。生态文明在理论上处于确立时期,在实践上处于起步阶段,关于生态文明的概念定义远未达成一致而体现出多样性。生态文明建设应以落实科学发展观为前提,着重从人们思想观念、生产发展方式、政府的政策、法律制度等方面着手,重点抓好“三个体系”建设。     

Male competition in Cardiocondyla ants

The two types of males in the ant genus Cardiocondyla differ remarkably in morphology and behavior. Ergatoid males are wingless fighters whose spermatogenesis continues throughout their entire adult lives and which therefore have an “unlimited” sperm supply. They attempt to kill all eclosing ergatoid rivals and thus to increase their share in copulations with the virgin queens reared in their nests. Winged males, on the other hand, are docile and emigrate from the nests a few days after eclosion, probably to mate with queens from other colonies. By this time, their testes have fully degenerated and all sperm is stored in the seminal vesicles. Before emigration, winged males may mate with virgin queens in their maternal nests, but they are nevertheless rarely attacked by ergatoid males. In the laboratory, the life expectancy of ergatoid males is only slightly higher than that of winged males, but because of the emigration of the latter the difference is likely to be more pronounced in the field. Both male morphs are capable of inseminating more than 35 virgin queens. However, winged males older than 14 days mate less often than ergatoid males of similar age, probably due to sperm depletion in later life. The spermathecae of queens inseminated by ergatoid males contained significantly more sperm than those of queens which mated with winged males. We discuss the evolution of intranidal mating and male polymorphism in ants. Received: 8 August 1997 / Accepted after revision: 6 October 1997