School of Biology and Environmental Science, Queensland University of Technology (QUT), Brisbane, QLD 4000, Australia.
J Insect Physiol. 2020 Apr;122:104024. doi: 10.1016/j.jinsphys.2020.104024. Epub 2020 Feb 12.
Olfaction is an essential sensory modality of insects which is known to vary with age. In short-lived insects odour response generally declines rapidly with increasing age, but how increasing age affects the olfactory response of long-lived insects is less known and there may be different life-time patterns of olfactory response. Here, we examine the effect of age on olfactory response and exploratory activity of a long-lived tephritid fruit fly, Bactrocera tryoni from sexual maturity (3 weeks) to advanced age (15 weeks). Males were tested against a male-specific attractant, cue-lure, which is associated with courtship and sexual selection in this species; while females were tested against guava-juice, a highly attractive oviposition host fruit odour. Trials were done in the laboratory using a Y-tube olfactometer at three weekly intervals. The probability of olfactory response of both males and females to tested odours declined with age. Males retained a constant attraction to cue-lure until 12 weeks of age, but then showed a significant drop in olfactory response at 15 weeks. However, females showed the highest attraction to guava-juice odour until six weeks of age and declined gradually thereafter. The change on odour response over time can be associated with an age-related change in initial locomotor activity for females as there was no change, over the life of the experiment, in selective female orientation to the odour source once flies started exploring within the olfactometer. However, for 15 week-old males, there was a simultaneous drop in both locomotor activity and selective olfactory orientation. The consistent attraction of male to cue-lure might be related to life-long reproductive activities of males, as males are thought to mate continuously during life. On the other hand, females' highest attraction to guava-juice odour in early life followed by a gradual decline might be linked with their oviposition rate which peaks in early life.
嗅觉是昆虫的一种重要感觉模式，其随年龄的变化而变化。在寿命较短的昆虫中，气味反应通常会随着年龄的增长而迅速下降，但随着年龄的增长如何影响寿命较长的昆虫的嗅觉反应知之甚少，并且嗅觉反应可能存在不同的终生模式。在这里，我们研究了年龄对长寿命桔小实蝇（Bactrocera tryoni）嗅觉反应和探索活动的影响，该桔小实蝇从性成熟（3 周）到老年（15 周）。雄性对雄性特异性引诱剂 cue-lure 进行了测试，cue-lure 与该物种的求偶和性选择有关；而雌性则对番石榴汁进行了测试，番石榴汁是一种极具吸引力的产卵宿主水果气味。在实验室中，使用 Y 型嗅觉仪，每三周进行一次试验。雌雄对测试气味的嗅觉反应概率随年龄的增长而降低。雄性对 cue-lure 的吸引力一直保持到 12 周龄，但在 15 周龄时嗅觉反应显著下降。然而，雌性对番石榴汁气味的吸引力最高，直到 6 周龄，然后逐渐下降。随着时间的推移，气味反应的变化可能与雌性初始运动活性的年龄相关变化有关，因为在实验过程中，一旦苍蝇在嗅觉仪内开始探索，对气味源的选择性雌性定向就没有变化。然而，对于 15 周龄的雄性，运动活性和选择性嗅觉定向同时下降。雄性对 cue-lure 的持续吸引力可能与雄性终生的生殖活动有关，因为雄性被认为在其一生中会不断交配。另一方面，雌性在早期对番石榴汁气味的最大吸引力随后逐渐下降，这可能与它们的产卵率有关，产卵率在早期达到峰值。
