Department of Biology, University of North Carolina at Greensboro, 235 Eberhart Bldg., Greensboro, North Carolina, United States of America.
Department of Entomology and Plant Pathology, North Carolina State University, Raleigh, North Carolina, United States of America.
PLoS Negl Trop Dis. 2019 Mar 5;13(3):e0007165. doi: 10.1371/journal.pntd.0007165. eCollection 2019 Mar.
Phlebotomine sand flies are vectors of human leishmaniases, important neglected tropical diseases. In this study, we investigated diel patterns of oviposition behavior, effects of visual cues on oviposition-site selection, and whether these affect the attraction of gravid Phlebotomus papatasi (Scopoli), the vector of old-world cutaneous leishmaniasis, to olfactory cues from oviposition sites.
METHODOLOGY/PRINCIPAL FINDINGS: To evaluate these questions, we conducted a series of experiments using attraction and oviposition assays within free-flight test chambers containing gravid females entrained under a 14:10 hrs light:dark photoperiod. By replacing sticky-screens or moist filter papers every three hours, we showed that oviposition site search occurs mainly in the latest part of the night whereas peak oviposition occurs during the early part of the night. Behavioral responses to olfactory oviposition cues are regulated by time-of-day and can be disrupted by transient exposure to a constant darkness photoperiod. Gravid females, but not any other stage, age, or sex, were attracted to dark, round oviposition jars, possibly resembling rodent burrow openings. This visual attraction disappeared in the absence of an illumination source. Egg deposition rate was not affected by jar color. Olfactory cues had the strongest effect when the visual cues were minimal.
Our study showed, for the first time, that visual cues in the form of oviposition-site color, lighting level, and photoperiod are important in guiding the oviposition behavior of phlebotomine sand flies. Furthermore, such visual cues could modify the flies' sensitivity to olfactory oviposition cues. Our results suggest that chemosensory and visual cues are complementary, with visual cues used to orient gravid females towards oviposition sites, possibly at long- to medium-ranges during crepuscular periods, while olfactory cues are used to approach the burrow in darkness and assess its suitability at close-range. Implications to sand fly control are discussed.
白蛉是人类利什曼病的传播媒介，是重要的被忽视热带病。在这项研究中，我们调查了产卵行为的昼夜节律模式、视觉线索对产卵场所选择的影响，以及这些因素是否会影响到传播旧世界皮肤利什曼病的埃及伊蚊对产卵场所嗅觉线索的吸引力。
方法/主要发现：为了评估这些问题，我们在包含被 14:10 小时光照：黑暗光周期驯化的孕蚊的自由飞行测试室中进行了一系列使用吸引和产卵测定的实验。通过每三小时更换粘性屏幕或湿润滤纸，我们表明产卵场所搜索主要发生在夜间的最后部分，而产卵高峰发生在夜间的早期。对嗅觉产卵线索的行为反应受时间的调节，并可能因短暂暴露于持续黑暗的光周期而中断。只有孕蚊，而不是其他任何阶段、年龄或性别，会被黑暗的圆形产卵罐吸引，这可能类似于啮齿动物洞穴的开口。这种视觉吸引力在没有照明源的情况下消失了。卵的沉积率不受罐颜色的影响。当视觉线索最小时，嗅觉线索的影响最大。
我们的研究首次表明，以产卵场所颜色、光照水平和光周期形式出现的视觉线索在指导白蛉的产卵行为方面非常重要。此外，这种视觉线索可以改变苍蝇对嗅觉产卵线索的敏感性。我们的研究结果表明，化学感觉和视觉线索是互补的，视觉线索用于引导孕蚊朝向产卵场所，可能在黄昏期间的长距离到中距离，而嗅觉线索用于在黑暗中接近洞穴，并在近距离评估其适宜性。讨论了对白蛉控制的影响。
