Implications of climate change for potamodromous fishes

There is little understanding of how climate change will impact potamodromous freshwater fishes. Since the mid 1970s, a decline in annual rainfall in south‐western Australia (a globally recognized biodiversity hotspot) has resulted in the rivers of the region undergoing severe reductions in surface flows (ca. 50%). There is universal agreement amongst Global Climate Models that rainfall will continue to decline in this region. Limited data are available on the movement patterns of the endemic freshwater fishes of south‐western Australia or on the relationship between their life histories and hydrology. We used this region as a model to determine how dramatic hydrological change may impact potamodromous freshwater fishes. Migration patterns of fishes in the largest river in south‐western Australia were quantified over a 4 year period and were related to a number of key environmental variables including discharge, temperature, pH, conductivity and dissolved oxygen. Most of the endemic freshwater fishes were potamodromous, displaying lateral seasonal spawning migrations from the main channel into tributaries, and there were significant temporal differences in movement patterns between species. Using a model averaging approach, amount of discharge was clearly the best predictor of upstream and downstream movement for most species. Given past and projected reductions in surface flow and groundwater, the findings have major implications for future recruitment rates and population viabilities of potamodromous fishes. Freshwater ecosystems in drying climatic regions can only be managed effectively if such hydro‐ecological relationships are considered. Proactive management and addressing existing anthropogenic stressors on aquatic ecosystems associated with the development of surface and groundwater resources and land use is required to increase the resistance and resilience of potamodromous fishes to ongoing flow reductions.     

Mutation frequency decline following chemical mutagenesis of Salmonella typhimurium

The occurrence is reported of a mutation frequency decline process (MFD) following treatment of Salmonella typhimurium strain trpC₃ with two chemical mutagens which give rise predominantly to suppressor revertants. With the carcinogen 4-nitroquinoline-N-oxide (4NQO) the results are analogous to those obtained for UV-mutagenesis. In the case of methoxynamine, the process is due to specific excision of premutational lesions, since lethality is low and lethal lesions are non-excisable. Mutants are described which cannot perform MFD of lesions induced by one or both of the chemical mutagens, indicating that the loss of revertants is in each case due to a bacteial repair system rather than to spontaneous degradation of the induced lesion. The mutants, however, were isolated because of an altered response to UV mutagenesis, viz., their ability to express UV-induced mutants in the absence of amino acids to stimulate active post-irradiation protein synthesis. In all other respects tested, their response to UV is identical with that of the parent strain. The hypothesis is discussed that the total absence of UV-induced revertants of the strain S. typhimurium trpC₃ when active protein synthesis is inhibited is due to two processes, first, rapid MFD due to the specific excision of pyrimidine dimers (the predominant UV-lesion) and secondly, the slow excision of other premutational damage which may be other photoproducts or secondary distortions caused by close juxtaposition of several pyrimidine dimers.     

Climate sensitivity of conifer growth doesn’t reveal distinct low–high dipole along the elevation gradient in the Wolong National Natural Reserve,SW China

Recent climate warming is usually hypothesized to cause tree growth decline in the semi-arid regions where forests are particularly vulnerable to warming induced increases of water deficit. But there is still a large knowledge gap of climate warming effects on tree growth of cold temperate forest in the sub-humid region. Here we assess how climate warming has affected tree growth in the Wolong National Natural Reserve, Southwestern China, where recent warming might not cause tree growth decline because of the cold-humid climatic conditions. Tree-ring data from four co-dominant coniferous species (Larix potaninii var. macrocarpa, Tsuga chinensis, Abies faxoniana and Juniperus saltuaria) along an elevation gradient (from 2700 m to 3700 m) all imprinted temperature signals, and were both positively and significantly correlated with instrumental record of temperature data during the analyzed period of 1954–2010. Furthermore, the rising temperature since 1980 induced pervasive tree growth increases and stronger temperature signals for the coniferous species along the elevation gradient. The tree-ring chronology recorded a strong coherence with instrumental temperature since 1980 and was successful to keep up with the pace of climate warming rate. If climate warming continues, further increases in forest growth could be expected, and the terrestrial carbon sink will be strengthened for the local forest ecosystem in the future.     

传粉昆虫下降背景下的授粉生态弹性: 内涵、机制和展望

全球传粉昆虫多样性正在下降, 如何保障农林生态系统传粉功能是当前研究的热点。理论上说, 传粉功能不仅与生态系统的传粉昆虫多样性相关, 还与生态系统的调节能力有关。近年来, 学者们逐渐认识到授粉生态弹性对传粉功能的影响。本文在回顾已有研究的基础之上, 总结传粉昆虫授粉生态弹性的内涵, 厘清授粉生态弹性与工程弹性、稳定性和抗性的异同。目前, 学者对授粉生态弹性形成机制开展广泛探讨, 提出功能冗余假说、密度补偿假说、响应多样性假说、连接周转假说和跨尺度弹性假说, 但这5个假说间的关系仍不清楚, 存在一词多义、词意混淆等现象。我们依次阐述功能冗余假说、密度补偿假说、响应多样性假说、连接周转假说和跨尺度弹性假说, 介绍不同假说中授粉生态弹性形成过程、研究热点和发展动态。通过解析授粉生态弹性的形成机制可知, 5个假说在内涵上存在紧密联系, 它们从不同空间尺度和研究对象下解释传粉昆虫授粉生态弹性的形成机制。未来授粉生态弹性研究将整合传粉昆虫群落动态和传粉功能动态的量化方法, 通过实验验证5个假说的合理性, 并揭示不同假说间的联系, 由此阐明授粉生态弹性的发生条件、形成阈值和动态规律。随着研究的深入, 授粉生态弹性理论有望用于指导农林生态系统传粉功能的经营管理。     

Macrophage inhibitory cytokine‐1 is associated with cognitive impairment and predicts cognitive decline – the Sydney Memory and Aging Study

Higher levels of macrophage inhibitory cytokine‐1, also known as growth differentiation factor 15 (MIC‐1/GDF15), are associated with adverse health outcomes and all‐cause mortality. The aim of this study was to examine the relationships between MIC‐1/GDF15 serum levels and global cognition, five cognitive domains, and mild cognitive impairment (MCI), at baseline (Wave 1) and prospectively at 2 years (Wave 2), in nondemented participants aged 70–90 years. Analyses were controlled for age, sex, education, Framingham risk score, history of cerebrovascular accident, acute myocardial infarction, angina, cancer, depression, C‐reactive protein, tumor necrosis factor‐α, interleukins 6 and 12, and apolipoprotein ε4 genotype. Higher MIC‐1/GDF15 levels were significantly associated with lower global cognition at both waves. Cross‐sectional associations were found between MIC‐1/GDF15 and all cognitive domains in Wave 1 (all P < 0.001) and between processing speed, memory, and executive function in Wave 2 (all P < 0.001). Only a trend was found for the prospective analyses, individuals with high MIC‐1/GDF15 at baseline declined in global cognition, executive function, memory, and processing speed. However, when categorizing MIC‐1/GDF15 by tertiles, prospective analyses revealed statistically significant lower memory and executive function in Wave 2 in those in the upper tertile compared with the lower tertile. Receiver operating characteristics (ROC) analysis was used to determine MIC‐1/GDF15 cutoff values associated with cognitive decline and showed that a MIC‐1/GDF15 level exceeding 2764 pg/ml was associated with a 20% chance of decline from normal to MCI or dementia. In summary, MIC‐1/GDF15 levels are associated with cognitive performance and cognitive decline. Further research is required to determine the pathophysiology of this relationship.     

Heavy metal pollution negatively correlates with anuran species richness and distribution in south‐eastern Australia

Heavy metal pollution has likely played an important role in global biodiversity decline, but there remains a paucity of information concerning the effects of metals on amphibian diversity. This study assessed anuran species richness and distribution in relation to sediment metal content and water chemistry in wetlands located along the Merri Creek corridor in Victoria, south‐eastern Australia. Anurans were present in 60% (21/35) of study sites, with a total of six species detected: the eastern common froglet (Crinia signifera), the eastern sign‐bearing froglet (Crinia parinsignifera), the southern brown tree frog (Litoria ewingii), the growling grass frog (Litoria raniformis), the eastern banjo frog (Limnodynastes dumerilii) and the spotted marsh frog (Limnodynastes tasmaniensis). Mean species richness was 1.77 ± 0.32 per site, and species richness ranged from zero to six species per site. Across sites, species richness correlated negatively with sediment concentrations of six heavy metals: copper, nickel, lead, zinc, cadmium and mercury. Species richness also correlated negatively with wetland water electrical conductivity (a proxy for salinity) and concentrations of orthophosphate. Distributions of the three most commonly observed frog species (C. signifera, L. tasmaniensis and L. ewingii) were significantly negatively associated with the total level of metal contamination at individual sites. The study is the first to provide evidence for an association between metal contamination and anuran species richness and distribution in the southern hemisphere, adding to a small but growing body of evidence that heavy metal pollution has contributed to global amphibian decline.     

Neuroprotective activities of bacopa,lycopene, astaxanthin, and vitamin B12 combination on oxidative stress-dependent neuronal death

Oxidative stress is considered the common effector of the cascade of degenerative events in many neurological conditions. Thus, in this paper we tested different nutraceuticals in H₂O₂ in vitro model to understand if could represent an adjuvant treatment for neurological diseases. In this study, nutraceuticals bacopa, lycopene, astaxanthin, and vitamin B12 were used alone or in combination in human neuronal differentiated SH-SY5Y cells upon hydrogen peroxide-induced injury and neuroprotective, neuronal death pathways were analyzed. The nutraceuticals analyzed were able to protect H₂O₂ cytotoxic effects, through increasing cell viability and proteins involved in neuroprotection pathways and restoring proteins involved in cell death pathways. On this basis, it is possible to propose the use of these compounds as dietary supplement for the prevention or as adjuvant to the only symptomatic treatments so far available for neurodegenerative diseases.     

Host thermoregulatory constraints predict growth of an amphibian chytrid pathogen (Batrachochytrium dendrobatidis)

1. The course and outcome of many wildlife diseases are context-dependent, and therefore change depending on the behaviour of hosts and environmental response of the pathogen.2. Contemporary declines in amphibian populations are widely attributed to chytridiomycosis, caused by the pathogenic fungus Batrachochytrium dendrobatidis. Despite the thermal sensitivity of the pathogen and its amphibian hosts, we do not understand how host thermal regimes experienced by frogs in the wild directly influence pathogen growth.3. We tested how thermal regimes experienced by the rainforest frog Litoria rheocola in the wild influence pathogen growth in the laboratory, and whether these responses differ from pathogen growth under available environmental thermal regimes.4. Frog thermal regimes mimicked in the laboratory accelerated pathogen growth during conditions representative of winter at high elevations more so than if temperatures matched air or stream water temperatures. By contrast, winter frog thermal regimes at low elevations slowed pathogen growth relative to air temperatures, but not water temperatures.5. The growth pattern of the fungus under frog thermal regimes matches field prevalence and intensity of infections for this species (high elevation winter > high elevation summer > low elevation winter > low elevation summer), whereas pathogen growth trajectories under environmental temperatures did not match these patterns.6. If these laboratory results translate into field responses, tropical frogs may be able to reduce disease impacts by regulating their body temperatures to limit pathogen growth (e.g., by using microhabitats that facilitate basking to reach high temperatures); in other cases, the environment may limit the ability of frogs to thermoregulate such that individuals are more vulnerable to this pathogen (e.g., in dense forests at high elevations).7. Species-specific thermoregulatory behaviour, and interactions with and constraints imposed by the environment, are therefore essential to understanding and predicting the spatial and temporal impacts of this global disease.