The effect of extreme environmental temperature spikes on mosquito longevity, fertility and ability to transmit viruses

背景和新颖性寿命、生殖力和媒介能力是影响蚊子地理分布范围及其所传播病毒流行病学的核心因素。通常，这些特征要么在高度控制的实验室条件下进行研究，要么在没有实验的情况下在实地环境中进行较为松散的观察。在果蝇中，雄性往往在比致死极限低几度的温度下绝育，导致环境导致它们的地理范围受到限制。相反，在库蠓中，热浪增加了病毒的能力。如果存在于蚊子中，它们将对媒介和病毒的范围产生不同的影响。在本项目中，学生将结合实地收集和实验室实验，了解自然热浪对英国本土的两种物种：库蚊和碎纹黄纹库蚊的影响。1)在实验室中，学生将对殖民地库蚊进行具有英国热浪代表性的热冲击，并评估对死亡率和繁殖力的影响，以估计热耐受性。2)根据这些结果，将对种群蚊子施加亚致死（热浪代表性）温度。然后用Usutu病毒挑战蚊子，以调查环境诱导的媒介能力。3)酷暑过后，野外采集野生库蚊、幼纹库蚊。将对结果成人的生育能力、死亡率和Usutu病毒感染情况进行评估。4)在实验暂停期间，学生将接受气候建模方面的培训，并使用他们的实验结果来模拟这两种物种在英国现在和未来气候情景下的热范围、地理限制和病毒传播。作为气候变化的直接后果，蚊子的可居住范围目前正在迅速变化。蚊子正在从一些气温上升、降雨减少的热带地区消失。相反，温带蚊子正在向两极传播，带来了重要的动物和人类病毒。它们所面临的不同环境条件将决定它们新的地理范围。由于气候变化，全球气温、热浪、湿度和降水模式发生了广泛而不均匀的变化，导致蚊子及其病毒从一些温度过高、降雨量过低的热带地区向两极地区普遍移动，转向更温和的气候。例如，近年来，乌苏图病毒（USUV）等人畜共患病毒在整个欧洲大陆传播，并于2020年在英国被发现。先前对不同昆虫的研究显示了热浪的不同影响，例如，与雄性果蝇相比，叮咬蠓的病毒传播量增加，而雄性果蝇的不育程度低于致死极限几度。对蚊子的类似影响可能对媒介、病毒的地理范围以及谁和哪里有风险产生影响。本研究的目的是确定哪些相关的温度依赖性状，如寿命、生育力和媒介能力，受到环境温度峰值（热浪）的影响。我将在殖民地和野生捕获的个体中使用英国本土的媒介物种库蚊和碎纹革蠓。通过对库蚊种群进行具有英国热浪代表性的热冲击，确定温度对死亡率和生育力的影响，以估计热耐受性并了解自然热浪的影响。在确定可存活的亚致死温度后，将对蚊子进行USUV挑战，以评估环境诱导的媒介能力可能性。这些发现将与现场收集的库蚊和

Background and noveltyLongevity, fertility and vector competence are central factors in the geographic range of mosquitoes and the epidemiology of the viruses they transmit. Typically, these traits are studied either in highly controlled laboratory conditions, or observed more loosely in field settings without experimentation. In Drosophila, males are often sterilised by temperatures several degrees lower than their lethal limit, resulting in environment-induced restriction of their geographic range. Conversely, in Culicoides biting midges, heatwaves increase competence for viruses. If present in mosquitoes, these would have contrasting effects on the ranges of vector and virus.ObjectivesIn this project, the student will combine field collection and laboratory experimentation to understand the effect of natural heat waves on two native UK species: Culex pipiens pipiens, and Ochlerotatus detritus.1) In the lab, the student will administer UK-heatwave representative thermal-shocks to colony Culex mosquitoes and assess the effects on mortality and fertility, to enable estimation of thermal tolerance.2) Using these results, sub-lethal (heatwave representative) temperatures will be administered to colony mosquitoes. Mosquitoes will then be challenged with Usutu virus, to investigate environmentally induced vector competence.3) Wild Culex pipiens pipiens, and Ochlerotatus detritus immatures will be collected from field sites after heatwaves. Resultant adults will be assessed for fertility, mortality and challenged with Usutu virus.4) During experimental downtime, the student will be trained in climate modelling and use their experimental results to model the thermal range, geographic limitations, and virus transmission of these two species in the UK, both now and under future climate scenarios.TimelinessAs a direct consequence of climate change, the habitable range for mosquitoes is currently changing rapidly. Mosquitoes are disappearing from some tropical regions where temperatures are increasing and rainfall reducing. Conversely, temperature mosquitoes are spreading polewards, bringing with them important animal and human viruses. The different environmental conditions they face will determine their new geographic ranges.As a result of climate change, there has been extensive and uneven changes in global temperature, heatwave, humidity, and precipitation patterns leading to the general movement of mosquitoes and their viruses, poleward, away from some tropical regions where temperature is too high and rainfall too low toward more temperate climates. For example, in recent years, there has been a spread of zoonotic viruses such as Usutu virus (USUV) throughout mainland Europe, with its detection in the UK occurring in 2020. Previous studies in different insects have shown contrasting effects of heatwaves, e.g., biting midges showing increased transmission of viruses in comparison to male fruit flies that become sterile several degrees below their lethal limit. Similar effects in mosquitoes could have implications on the geographic ranges of vectors, viruses, and who and where is at risk. The aim of this study is to determine which relevant temperature-dependent traits, such as longevity, fertility, and vector competence, are affected by spikes in environmental temperature (heatwaves). I will use the native UK vector species Culex pipiens and Ochlerotatus detritus, both in colony and wild-caught individuals. By administering UK-heatwave representative thermal shocks to colony Culex mosquitoes, temperature effects on mortality and fertility will be determined to estimate thermal tolerance and understand the effect of natural heatwaves. Following the identification of survivable sub-lethal temperatures, mosquitoes will then be challenged with USUV to assess vector competence possibilities induced by the environment. These findings will then be combined with field collected Culex and