Cordeschi Giulia, Mastrantonio Valentina, Bisconti Roberta, Giardiello Nicole, Canestrelli Daniele, Porretta Daniele
Department of Environmental Biology, Sapienza University of Rome, Rome, Italy.
Department of Ecology and Biology, Tuscia University, Viterbo, Italy.
Parasit Vectors. 2025 Jun 17;18(1):224. doi: 10.1186/s13071-025-06875-z.
The pupal stage in holometabolous insects is a critical transition between larval and adult forms, during which feeding ceases and survival depends on stored energy reserves. Mosquito pupae exhibit active diving behaviour in response to threats, which is energetically costly due to their positive buoyancy. Whether pupae are able to adjust diving behaviour according to environmental conditions, balancing predator avoidance and energy expenditure, remains poorly understood. Here, we investigated how water salinity affects the diving behaviour of Aedes mariae pupae, a species inhabiting Mediterranean rock pools characterised by highly variable salinity conditions.
Pupae were maintained and tested in two salinity conditions: low (50%) and high (150%). Diving behaviour was recorded following an automated mechanical stimulus, and we measured: (i) time spent underwater, (ii) pupal activity (i.e. the number of abdominal movements during the immersion and the ratio of movements to time spent underwater) and (iii) the proportion of time spent by a pupa at different depths along the height of the water column (space use).
We found that pupae in high-salinity conditions spent 20.6% less time underwater than those in low salinity. They also performed fewer abdominal movements during dives but showed no significant differences in movements per unit time. Analysis of space use showed that pupae in high salinity spent more time in the upper part of the water column and less time in the middle and lower parts.
Ae. mariae pupae modify their diving behaviour in response to different salinity conditions, adopting energy-efficient responses to external stimuli that promote survival in variable habitats. These findings highlight the importance of pupal behavioural flexibility for overall fitness and underscore the need to investigate pupal behavioural plasticity, which remains largely unexplored.
全变态昆虫的蛹期是幼虫和成虫形态之间的关键过渡阶段，在此期间停止进食，生存依赖于储存的能量储备。蚊蛹在受到威胁时会表现出活跃的潜水行为，由于其正浮力，这种行为在能量上代价高昂。蛹是否能够根据环境条件调整潜水行为，平衡躲避捕食者和能量消耗，目前仍知之甚少。在这里，我们研究了水的盐度如何影响玛丽伊蚊蛹的潜水行为，玛丽伊蚊栖息在地中海岩池中，那里的盐度条件变化很大。
将蛹置于两种盐度条件下进行饲养和测试：低盐度（50%）和高盐度（150%）。在自动机械刺激后记录潜水行为，我们测量了：（i）在水下的时间；（ii）蛹的活动（即浸没期间腹部运动的次数以及运动次数与在水下时间的比率）；（iii）蛹在水柱高度不同深度所花费时间的比例（空间利用情况）。
我们发现，处于高盐度条件下的蛹在水下的时间比低盐度条件下的蛹少20.6%。它们在潜水时腹部运动也较少，但单位时间内的运动没有显著差异。空间利用情况分析表明，高盐度条件下的蛹在水柱上部花费的时间更多，在中部和下部花费的时间更少。
玛丽伊蚊蛹会根据不同的盐度条件改变其潜水行为，对外部刺激采取节能反应，以促进在多变栖息地中的生存。这些发现突出了蛹行为灵活性对整体适应性的重要性，并强调了研究蛹行为可塑性的必要性，而这在很大程度上仍未得到探索。
