Differential recovery ability from infections by two blood parasite genera in males of a Mediterranean lacertid lizard after an experimental translocation

Different blood parasites can co-infect natural populations of lizards. However, our knowledge on the host’s ability to recover from them (i.e., significantly reduce parasitaemia levels) is scarce. This has interest from an ecological immunology perspective. Herein, we investigate the host recovery ability in males of Psammodromus algirus infected by parasite genera Schellackia and Karyolysus. The role of lizard hosts is dissimilar in the life cycle of these two parasites, and thus different immune control of reproduction cycles by the vertebrate hosts is expected. As Schellackia performs both sexual and asexual reproduction cycles in lizards, we expect a better immune control by its vertebrate hosts. On the contrary, Karyolysus performs sexual reproductive cycles in vectors, hence we expect lower immune control by the lizards. We carried out a reciprocal translocation experiment during the lizards’ mating season to evaluate both parasitaemia and leukocyte profiles in male lizards, being one of the sampling plots close to a road with moderate traffic. These circumstances provide a combination of extrinsic (environmental stress) and intrinsic factors (reproductive versus immune trade-offs) that may influence host’s recovery ability. We recaptured 33% of the lizards, with a similar proportion in control and translocated groups. Karyolysus infected 92.3% and Schellackia 38.5% of these lizards. Hosts demonstrated ability to significantly reduce parasitaemia of Schellackia but not of Karyolysus. This suggests, in line with our predictions, a differential immune relationship of lizards with these parasites, at time that supports that parasites with different phylogenetic origins should be analysed separately in investigations of their effects on hosts. Furthermore, lizards close to the road underwent a stronger upregulation of lymphocytes and monocytes when translocated far from the road, suggesting a putative greater exposure to pathogens in the latter area.多种血液寄生虫可共同感染蜥蜴的自然种群。然而，目前学界对于宿主摆脱此类寄生虫（即显著降低寄生虫血症水平）的能力的认知仍较为匮乏，这一研究空白从生态免疫学视角来看具有重要研究价值。在此，我们针对被谢拉虫属（Schellackia）与核体属（Karyolysus）寄生虫感染的阿尔及利亚直棱蜥（Psammodromus algirus）雄性个体的宿主恢复能力展开研究。这两类寄生虫在蜥蜴宿主的生活史中扮演的角色存在差异，因此脊椎动物宿主对二者繁殖周期的免疫调控机制也理应有所不同：由于谢拉虫属（Schellackia）在蜥蜴体内同时进行有性与无性繁殖周期，我们推测其脊椎动物宿主对该寄生虫的免疫调控能力更强；与之相反，核体属（Karyolysus）仅在媒介生物体内进行有性繁殖周期，因此我们推测蜥蜴宿主对其的免疫调控能力较弱。我们在蜥蜴的交配季开展了双向易地实验，以评估雄性蜥蜴的寄生虫血症水平与白细胞谱特征，其中一个样地毗邻交通量中等的道路。该实验设计结合了外源（环境压力）与内源（繁殖与免疫权衡）两类可能影响宿主恢复能力的因素。我们成功重捕了33%的受试蜥蜴，对照组与易地移植组的重捕比例相近。在重捕个体中，92.3%的个体感染了核体属（Karyolysus）寄生虫，38.5%的个体感染了谢拉虫属（Schellackia）寄生虫。宿主能够显著降低谢拉虫属（Schellackia）的寄生虫血症水平，但对核体属（Karyolysus）则无此能力。这一结果与我们的预测相符，表明蜥蜴与这两类寄生虫之间存在差异化的免疫互作关系；同时也印证了：在探究寄生虫对宿主的影响时，应针对不同系统发育起源的寄生虫分别开展分析。此外，原本栖息于道路附近的蜥蜴在被易地移植至远离道路的区域后，其淋巴细胞与单核细胞的上调幅度更为显著，这表明远离道路的区域可能存在更高的病原体暴露风险。