Posgrado en Ciencias Biológicas, Universidad Nacional Autónoma de México, Coyoacán, Mexico City, CDMX, Mexico.
Escuela Nacional de Estudios Superiores, Unidad Morelia, UNAM., Morelia, Michoacán, Mexico.
PLoS One. 2024 Mar 13;19(3):e0298400. doi: 10.1371/journal.pone.0298400. eCollection 2024.
Facultative parasites can alternate between a free-living and a parasitic existence to complete their life cycle. Yet, it remains uncertain which lifestyle they prefer. The optimal foraging theory suggests that food preferences align with fitness benefits. To test this hypothesis, we investigated the facultative parasite nematode Rhabditis regina, assessing its host preference and the associated benefits. Two experiments were conducted using wild nematode populations collected from Phyllophaga polyphylla, their natural host. In the first experiment, we used a behavioral arena to assess host preference between the natural host and two experimental hosts: Spodoptera frugiperda which is an alternative host and dead Tenebrio molitor, which simulates a saprophytic environment. In the second experiment, we subjected wild nematodes to "experimental evolution" lasting 50 generations in S. frugiperda and 53 generations in T. molitor carcass. We then compared life history traits (the size, survival, number of larvae, and glycogen and triglycerides as energy reserves) of dauer larvae with those nematodes from P. polyphylla (control group). We found a significant preference for P. polyphylla, which correlated with higher values in the nematode's life history traits. In contrast, the preference for S. frugiperda and the saprophytic environment was lower, resulting in less efficient life history traits. These findings align with the optimal foraging theory, as the nematode's parasitic preferences are in line with maximizing fitness. This also indicates that R. regina exhibits specificity to P. polyphylla and is better adapted to a parasitic lifestyle than a free-living one, suggesting an evolutionary pathway towards parasitism.
兼性寄生虫可以在自由生活和寄生生活之间交替，以完成其生命周期。然而，它们更喜欢哪种生活方式仍不确定。最佳觅食理论表明，食物偏好与适应度利益相一致。为了检验这一假设，我们研究了兼性寄生虫线虫 Rhabditis regina，评估了它的宿主偏好及其相关益处。使用从 Phyllophaga polyphylla 收集的野生线虫种群进行了两项实验，这是它们的天然宿主。在第一个实验中，我们使用行为竞技场来评估天然宿主与两个实验宿主之间的宿主偏好：替代宿主 Spodoptera frugiperda 和模拟腐生环境的死 Tenebrio molitor。在第二个实验中，我们将野生线虫置于“实验进化”中，在 S. frugiperda 中持续 50 代，在 T. molitor 尸体中持续 53 代。然后，我们比较了 dauer 幼虫的生活史特征（大小、存活率、幼虫数量以及糖原和甘油三酯作为能量储备）与来自 P. polyphylla 的线虫（对照组）。我们发现对 P. polyphylla 的明显偏好，这与线虫生活史特征的更高值相关。相比之下，对 S. frugiperda 和腐生环境的偏好较低，导致生活史特征效率较低。这些发现与最佳觅食理论一致，因为线虫的寄生偏好与最大限度地提高适应性相一致。这也表明 R. regina 对线虫 P. polyphylla 表现出特异性，并且比自由生活更适应寄生生活方式，表明向寄生进化的途径。
