Stange G, Monro J, Stowe S, Osmond C B
Research School of Biological Sciences, Australian National University, GPO Box 475, 2601, Canberra, ACT, Australia.
Department of Animal Science, The University of New England, 2351, Armidale, NSW, Australia.
Oecologia. 1995 Jun;102(3):341-352. doi: 10.1007/BF00329801.
The interaction between the moth, Cactoblastis cactorum, and the cactus, Opuntia stricta, is used as a model to examine the question of whether the CO sense of a herbivorous insect can detect the CO gradients associated with a plant's metabolic activity. Both the anatomical and the electrophysiological characteristics of CO-sensitive receptor neurons in C. cactorum indicate an adaptation to the detection of small fluctuations around the atmospheric background. Evidence is provided that further rises in background will impair the function of the sensory organ. In the habitat of the plant, during the diurnal window of the moth's activity, two types of CO gradients occur that are detectable by the moth's sensors. The first gradient, associated with soil respiration, is vertical and extends from the soil surface to an altitude of approximately 1 m. Its magnitude is well above the detectability limit of the sensors. The notion that this gradient provides, to a flying insect, a cue for the maintenance of a flight altitude favourable for host detection is supported by field observations of behaviour. The second gradient, associated with CO fixation by the plant, extends from the surfaces of photosynthetic organs (cladodes) over a boundary layer distance of approximately 5 mm. Again, its magnitude is well above the detectability limit. The notion that this gradient provides, to a walking insect, a cue to the physiological condition of the plant is supported by the observation that females of C. cactorum, prior to oviposition, actively probe the plant surface with their CO sensors. In a simulation of probing, pronounced responses of the sensors to the CO-fixing capacity of O. stricta are observed. We propose that by probing the boundary layer, females of C. cactorum can detect the healthiest, most active O. stricta cladodes, accounting for earlier observations that the most vigorous plants attract the greatest density of egg sticks.
蛾类昆虫仙人掌螟（Cactoblastis cactorum）与仙人掌（Opuntia stricta）之间的相互作用被用作一个模型，以研究植食性昆虫的一氧化碳（CO）感官是否能够检测与植物代谢活动相关的CO梯度这一问题。仙人掌螟中对CO敏感的受体神经元的解剖学和电生理特征均表明，其已适应于检测大气背景周围的微小波动。有证据表明，背景CO浓度的进一步升高将损害感觉器官的功能。在仙人掌的栖息地，在蛾类活动的白天时段，会出现两种可被蛾类传感器检测到的CO梯度。第一种梯度与土壤呼吸有关，是垂直的，从土壤表面延伸至约1米的高度。其强度远高于传感器的可检测极限。行为的野外观察结果支持了这样一种观点，即这种梯度为飞行中的昆虫提供了一个线索，有助于维持有利于宿主检测的飞行高度。第二种梯度与植物的CO固定有关，从光合器官（茎节）表面延伸约5毫米的边界层距离。同样，其强度也远高于可检测极限。仙人掌螟的雌性在产卵前会用其CO传感器主动探测植物表面，这一观察结果支持了这样一种观点，即这种梯度为行走中的昆虫提供了植物生理状况的线索。在一次模拟探测中，观察到传感器对仙人掌的CO固定能力有明显反应。我们提出，通过探测边界层，仙人掌螟的雌性能够检测到最健康、最活跃的仙人掌茎节，这与早期的观察结果相符，即最有活力的植物吸引的卵块密度最大。
