International Centre of Insect Physiology and Ecology (icipe), P.O Box 30772-00100, Nairobi, Kenya.
Kilimanjaro Christian Medical University College (KCMUCo), P.O Box 2240, Moshi, Tanzania.
Sci Rep. 2021 Jul 20;11(1):14785. doi: 10.1038/s41598-021-94043-5.
Gravid female Anopheles gambiae mosquitoes identify suitable oviposition sites through a repertoire of cues, but the influence of allelochemicals, especially root phytochemicals in modulating this behavior and impacting subsequent progeny bionomics remains unexplored. We addressed these questions in the malaria vector Anopheles gambiae and its invasive host plant Parthenium hysterophorus. Using chemical analysis combined with laboratory behavioral assays, we demonstrate that a blend of terpenes, namely α-pinene, α-phellandrene, β-phellandrene, 3-carene and (E)-caryophyllene emitted from P. hysterophorus root exudate treated-water attracted gravid females. However, fewer eggs (55%) hatched in this treatment than in control water (66%). The sesquiterpene lactone parthenin, identified in both the natural aquatic habitat harboring P. hysterophorus and root exudate-treated water was found to be responsible for the ovicidal effect. Moreover, larvae exposed to parthenin developed 2 to 3 days earlier but survived 4 to 5 days longer as adults (median larval survival time = 9 days (all replicates);11 to 12 days as adults) than the non-exposed control (median larval survival time = 11 days (reps 1 & 2), 12 days (rep 3); 6 to 7 days as adults). These results improve our understanding of the risk and benefits of oviposition site selection by gravid An. gambiae females and the role root exudate allelochemicals could play on anopheline bionomics, with potential implications in malaria transmission.
有生育能力的雌性冈比亚按蚊通过一系列线索来识别合适的产卵地点，但有关化学信号，尤其是根化感物质在调节这种行为以及影响后续后代生物学特性方面的影响仍未得到探索。我们在疟疾媒介冈比亚按蚊及其入侵性宿主植物假臭草中解决了这些问题。通过化学分析结合实验室行为测定，我们证明了假臭草根渗出物处理水中混合的萜烯，即α-蒎烯、α-水芹烯、β-水芹烯、蒈烯和(E)-石竹烯，吸引了有生育能力的雌性蚊子。然而，在这种处理中，只有 55%的卵孵化（66%）。在含有假臭草的天然水生栖息地和根渗出物处理水中均发现的倍半萜内酯除虫菊素是导致卵致死的原因。此外，接触除虫菊素的幼虫比未接触的对照组（幼虫的中位存活时间=9 天（所有重复）；成虫的中位存活时间=11 至 12 天）更早发育 2 至 3 天，但成虫的存活时间更长 4 至 5 天（幼虫的中位存活时间=11 天（重复 1 和 2），12 天（重复 3）；成虫的中位存活时间=6 至 7 天）。这些结果提高了我们对有生育能力的雌性冈比亚按蚊选择产卵地点的风险和益处的理解，以及根渗出物化感物质在按蚊生物学特性方面可能发挥的作用，这可能对疟疾传播产生影响。
