Centre of Applied Entomology and Parasitology, School of Life Sciences, Keele University, Newcastle-Under-Lyme, Staffordshire, UK.
Swiss Tropical and Public Health Institute, Kreuzgasse 2, 4123, Allschwil, Switzerland.
Parasit Vectors. 2024 Nov 20;17(1):478. doi: 10.1186/s13071-024-06533-w.
Eggs of anopheline mosquitoes hatch within a few days of laying and require high levels of humidity to survive. Assessing natural variation in egg hatching and its environmental and genetic determinants in sibling species of the malaria vector Anopheles gambiae s.l. is important for understanding their adaptation to variable aquatic habitats. Crucially, it can also inform insectary rearing practices toward the optimization of mosquito production for genetic vector control strategies.
Hatching rates and timing of egg hatching in long-established and recently colonized strains of An. gambiae s.s, Anopheles arabiensis, and Anopheles coluzzii, were compared under still water conditions (26 ℃) and with cold (4 ℃) and (15 ℃) water agitation regimes. Next, early and late hatching strains of the recently colonized An. coluzzii VK colony were generated through bidirectional selection for 18-23 generations to detect a genetic component for this trait.
Hatching rates differed significantly between species and treatments. The older An. arabiensis Senn and An. gambiae s.s. Kisumu strains had the highest proportion of hatching and preferred the nonagitation treatment at 26 °C. In contrast, the more recently colonized An. coluzzii VK and An. arabiensis Rufisque strains had lower overall hatching success but responded strongly to agitation at 4 °C, while the An. coluzzii Mopti strain did not significantly respond to water agitation. In all strains, eggs hatching started at day 2 and continued till day 5 in the older strains, whilst it was more staggered and extended up to day 6 in the younger strains. Bidirectional selection for early and late hatching over many generations resulted in early hatching selected strains with eggs hatching 2-3 days earlier than in late hatching ones indicating a significant heritable component for these traits.
Water agitation and temperature and age of colonization are likely important determinants of egg hatching in natural An. gambiae s.l.
Current rearing protocols systematically select for fast hatching and result in the progressive loss of staggered egg hatching in older laboratory strains. The selection of novel slow-hatching strains may prove instrumental to enable the mass production, shipping, and release of Anopheles mosquitoes across Africa as part of genetic vector control programs.
按蚊的卵在产下几天后孵化，需要高湿度才能存活。评估疟疾病媒按蚊属的姐妹种在自然环境中的卵孵化及其环境和遗传决定因素，对于了解它们对可变水生栖息地的适应能力非常重要。至关重要的是，这也可以为昆虫饲养实践提供信息，以优化蚊子的生产，从而实现遗传媒介控制策略。
在静水条件（26°C）和冷水（4°C）和（15°C）水搅拌条件下，比较了按蚊属 s.s、阿拉伯按蚊、和库蚊的长期建立和最近殖民的品系的孵化率和孵化时间。接下来，通过对最近殖民的 An. coluzzii VK 品系的早孵和晚孵品系进行 18-23 代的双向选择，以检测该性状的遗传成分。
不同物种和处理之间的孵化率有显著差异。较老的 An. arabiensis Senn 和 An. gambiae s.s. Kisumu 品系的孵化比例最高，在 26°C 时更喜欢非搅拌处理。相比之下，最近殖民的 An. coluzzii VK 和 An. arabiensis Rufisque 品系的整体孵化成功率较低，但对 4°C 的搅拌反应强烈，而 An. coluzzii Mopti 品系对水搅拌没有显著反应。在所有品系中，卵孵化从第 2 天开始，在较老的品系中持续到第 5 天，而在较年轻的品系中则更为分散，持续到第 6 天。经过多代的早孵和晚孵双向选择，早孵选系的卵孵化时间比晚孵选系早 2-3 天，表明这些性状具有显著的遗传成分。
水搅拌、温度和殖民化的年龄可能是自然存在的按蚊属 s.l. 卵孵化的重要决定因素。
目前的饲养方案系统地选择快速孵化，并导致较老实验室品系中孵化时间的逐渐延长。选择新型的慢孵化品系可能有助于在非洲大规模生产、运输和释放按蚊作为遗传媒介控制计划的一部分。
