Population size regulation is density-dependent in Rhodnius prolixus (Hemiptera: Reduviidae) through an irritability mechanism

BACKGROUND Physical factors can determine the level of triatomine abundance, but do not regulate their population densities, and neither do natural enemies. OBJECTIVES To identify the processes associated with density-dependent triatomine population regulation. METHODS We set-up a laboratory experiment with four interconnected boxes; the central box harbored Rhodnius prolixus bugs and one hamster. Stage 5 and adult densities of 10, 20, 30, 40, and 60 bugs per hamster, were replicated four times (except the density of 60 bugs). Hamster’s irritability and several triatomine responses were measured: feeding, development time and longevity, mortality, fecundity, dispersal, and the net reproductive value (R o ). FINDINGS Density had a statistically significant effect on irritability, but not on the percent of bugs feeding. Density was significant on blood meal size ingested in bugs that did not move between boxes, but not significant when the bugs moved. Density and irritability affected the proportion of stage 5 nymphs molting, and the proportion of adult bugs dying per day and over a three-week period. There was a highly significant effect of density and irritability on R o . MAIN CONCLUSIONS We showed that a density-dependent mechanism, acting through the irritability of the host, seems the most plausible process regulating populations in triatomines.

背景 物理因素可决定锥蝽(triatomine)的种群丰度水平，但无法调控其种群密度，天敌亦然。
研究目标 明确与密度依赖型锥蝽种群调控相关的过程。
研究方法 本研究设置了包含4个连通箱体的实验室实验：中央箱体饲养罗氏锥蝽(Rhodnius prolixus)与1只仓鼠。设置每只仓鼠对应10、20、30、40及60只第5龄若虫与成虫的密度梯度，每组重复4次（密度为60只的组除外）。记录仓鼠的激怒程度以及锥蝽的多项响应指标：取食情况、发育时长与寿命、死亡率、繁殖力、扩散行为，以及净生殖值(R₀)。
研究结果 种群密度对仓鼠的激怒程度具有统计学意义上的显著影响，但对锥蝽的取食率无显著影响。对于未在箱体间扩散的锥蝽，种群密度对其摄入的血餐体积存在显著影响，但对于发生扩散的锥蝽则无此效应。种群密度与仓鼠激怒程度均可影响第5龄若虫的蜕皮比例，以及每日及三周周期内的成虫死亡率。种群密度与仓鼠激怒程度对净生殖值(R₀)存在极显著影响。
主要结论 本研究证实，通过宿主激怒程度发挥作用的密度依赖机制，是调控锥蝽种群的最合理过程。