Environmental influences on fish cardiovascular function and control

鱼类具有真正的全球分布，生活在温度从-1.8摄氏度到42摄氏度的水域，这些水域可能只含有很少的氧气(即低氧)，并且盐分含量可能有很大差异(例如，河口)。此外，人类活动(包括加速的气候变化)给这些鱼类带来了额外的压力，在一些地区，这已导致物种流离失所或灭绝。如果鱼类要在这些环境变量的短期和长期变化中存活下来，促进向组织输送更多氧气的生理调节(例如，心脏泵送的更多血液、血液血红蛋白水平的增加、通风的调整、血流的重新分配)是至关重要的。事实上，有人提出，随着温度的升高，心脏功能的局限性是鱼类耐热性的主要决定因素。拟议的研究将为以下方面提供重要的见解：1)哪些因素(机制)在高温下限制鱼类的心脏功能；2)鱼类的免疫系统、应激生理和心血管功能之间的相互作用；3)为什么心脏功能在长期低氧适应后受损；以及4)有多少血液流入卵巢(卵)，是否可以控制，以及温度、水氧水平和盐度的变化如何影响心脏功能。后一项研究很重要，因为在不同的环境条件下维持对卵的氧气和营养输送可能对确保产生大量可存活的后代至关重要，从而确保鱼类种群的健康。

Fish have a truly global distribution and live in waters where temperatures range from -1.8 to 42oC, that can contain little to no oxygen (i.e., are hypoxic), and may vary dramatically in salt content (e.g., estuaries). Further, human activities (including accelerated climate change) are placing added pressures on these fish, and in some areas this has lead to the displacement or extinction of species. Physiological adjustments that promote an increase in oxygen delivery to the tissues (e.g. more blood pumped by the heart, an increase in blood haemoglobin levels, adjustments in ventilation, the redistribution of blood flow) are critical if fish are to survive short- and long-term variations in these environmental variables. Indeed, it has been suggested that limitations in cardiac function as temperatures increase are a primary determinant of a fish's thermal tolerance. The proposed research will provide important insights into: 1) what factors (mechanisms) limit heart function in fishes at high temperatures; 2) interactions between the fish's immune system, stress physiology and cardiovascular function; 3) why heart function is compromised following acclimation to prolonged hypoxia; and 4) how much blood flows to the ovaries (eggs), whether it can be controlled, and how it is impacted by changes in temperature, water oxygen levels and salinity. The latter studies are important because the maintenance of oxygen and nutrient delivery to the eggs under varied environmental conditions is likely vital to ensuring that a large number of viable offspring are produced, and thus, the health of fish populations.