Results of the lethal concentration 50 at 96 hours from Behavioural ecology meets oncology: quantifying the recovery of animal behaviour to a transient exposure to a cancer risk factor

Wildlife is increasingly exposed to sublethal transient cancer risk factors, including mutagenic substances, which activates their anti-cancer defences, promotes tumourigenesis, and may negatively impact populations. Little is known about how exposure to cancer risk factors impacts the behaviour of wildlife. Here, we investigated the effects of a sublethal, short-term exposure to a carcinogen at environmentally relevant concentrations on the activity patterns of wild <i>Girardia tigrina</i> planaria during a two-phase experiment, consisting of a 7-day exposure to cadmium period followed by a 7-day recovery period. To comprehensively explore the effects of the exposure on activity patterns, we employed the double hierarchical generalized linear model framework which explicitly models residual intraindividual variability in addition to the mean and variance of the population. We found that exposed planaria were less active compared to unexposed individuals and were able to recover to pre-exposure activity levels albeit with a reduced variance in activity at the start of the recovery phase. Planaria showing high activity levels were less predictable with larger daily activity variations and higher residual variance. Thus, the shift in behavioural variability induced by an exposure to a cancer risk factor can be quantified using advanced tools from the field of behavioural ecology. This is required to understand how tumourous processes affect the ecology of species.

野生动物正日益暴露于亚致死性短暂癌症风险因子之中，其中包括致突变物质（mutagenic substances）。这类因子可激活野生动物的抗癌防御机制、促进肿瘤发生，并可能对种群产生负面影响。目前学界对癌症风险因子暴露如何影响野生动物行为的认知仍较为匮乏。本研究通过两阶段实验——先为期7天的镉暴露阶段，再为期7天的恢复阶段——探究了环境相关浓度下亚致死短期致癌物暴露对野生<i>Girardia tigrina</i>涡虫活动模式的影响。为全面探究暴露对活动模式的影响，本研究采用了双分层广义线性模型（double hierarchical generalized linear model）框架，该框架不仅可对种群均值与方差进行建模，还能显式刻画个体内残差变异性。研究结果显示，与未暴露个体相比，暴露组涡虫的活动活跃度更低，但能够恢复至暴露前的活动水平，不过在恢复阶段初期其活动方差有所降低。活动水平较高的涡虫，其行为可预测性更低，且每日活动变异度更大、残差方差更高。因此，借助行为生态学领域的先进工具，可对癌症风险因子暴露所诱导的行为变异性变化进行量化。这一研究对于理解肿瘤发生过程如何影响物种生态学具有重要意义。