Dataset Sabbagh 2023

Studies of host physiology in response to parasite infection tend to focus on impacts at the whole-organism level such as aerobic metabolic rates, body condition, behavior, etc. Very few of these studies investigate cellular mechanisms that may very well explain alterations to metabolic rates and body condition often observed in infected organisms, and even fewer compare these cellular mechanisms across populations. Mitochondria are the organelles responsible for energy production and are linked to whole-animal metabolic rates as well as body condition. Mitochondria are also implicated in the production and regulation of reactive oxygen species, molecules that play an important role in cellular immune responses. In this manuscript, we studied the activity of some key metabolic and antioxidant enzymes in three populations of wild pumpkinseed sunfish (<i>Lepomis gibbosus</i><i> </i>(Linnaeus, 1758)) naturally infected by the bass tapeworm (<i>Proteocephallus ambloplitis</i> (Leidy, 1887)). Enzymatic activity was measured in the liver tissue, the most infected organ by the cestodes, and linked to infection intensity and fish body condition. We found that cestode infection was associated with reduced lipid metabolism and increased lactic fermentation, suggesting that infection may alter oxygen availability in host tissues. Additionally, population body condition varied differently with cestode density; positive as well as negative correlations where found, depending the population. Some enzymatic activity also varied among populations, such as the activity of the electron transport system and the antioxidant glutathione peroxidase, suggesting the adoption of different immunological responses. The differences could be attributed to ecological and demographic differences, factors that may influence the physiological effects and resistance of populations to parasite infections. These results highlight the importance of accounting for infection when studying animal physiology and we hope that the publication of this work will help guide future research on this topic.

针对宿主生理响应寄生虫感染的研究，往往聚焦于宿主整体层面的影响，例如有氧代谢速率、身体状况、行为模式等。此类研究中极少有探讨细胞机制的——而这类机制恰好可以解释感染宿主中常见的代谢速率与身体状况变化；更鲜有研究跨种群对比这些细胞机制。线粒体（mitochondria）是负责能量产生的细胞器，与动物整体代谢速率及身体状况密切相关。此外，线粒体还参与活性氧（reactive oxygen species）的产生与调控，这类分子在细胞免疫应答中发挥重要作用。本研究中，我们对3个野生南瓜籽太阳鱼（*Lepomis gibbosus*（Linnaeus, 1758））种群的关键代谢酶与抗氧化酶活性进行了测定，这些鱼自然感染了鲈鱼绦虫（*Proteocephallus ambloplitis*（Leidy, 1887））。我们在肝脏组织——绦虫感染程度最高的宿主器官——中测定了酶活性，并将其与感染强度及鱼体身体状况进行关联分析。研究结果显示，绦虫感染与脂质代谢水平降低、乳酸发酵增强相关，这表明感染可能会改变宿主组织内的氧气可用性。此外，不同种群的身体状况随绦虫感染密度的变化趋势存在差异：根据种群的不同，可观察到正相关与负相关两种关联模式。部分酶活性在种群间也存在差异，例如电子传递系统（electron transport system）活性与抗氧化酶谷胱甘肽过氧化物酶（glutathione peroxidase）活性，这表明不同种群采取了不同的免疫应答策略。这些差异可归因于种群间的生态学与种群统计学差异，这类因素会影响种群对寄生虫感染的生理效应与抗性水平。本研究结果凸显了在开展动物生理学研究时考虑感染因素的重要性，我们期望本研究成果能够为该领域的后续研究提供指引。