Wada-Katsumata Ayako, Schal Coby
Department of Entomology and Plant Pathology and W.M. Keck Center for Behavioral Biology, North Carolina State University, Raleigh, NC 27695, USA.
Insects. 2021 Mar 21;12(3):263. doi: 10.3390/insects12030263.
Saliva has diverse functions in feeding behavior of animals. However, the impact of salivary digestion of food on insect gustatory information processing is poorly documented. Glucose-aversion (GA) in the German cockroach, , is a highly adaptive heritable behavioral resistance trait that protects the cockroach from ingesting glucose-containing-insecticide-baits. In this study, we confirmed that GA cockroaches rejected glucose, but they accepted oligosaccharides. However, whereas wild-type cockroaches that accepted glucose also satiated on oligosaccharides, GA cockroaches ceased ingesting the oligosaccharides within seconds, resulting in significantly lower consumption. We hypothesized that saliva might hydrolyze oligosaccharides, releasing glucose and terminating feeding. By mixing artificially collected cockroach saliva with various oligosaccharides, we demonstrated oligosaccharide-aversion in GA cockroaches. Acarbose, an alpha-glucosidase inhibitor, prevented the accumulation of glucose and rescued the phagostimulatory response and ingestion of oligosaccharides. Our results indicate that pre-oral and oral hydrolysis of oligosaccharides by salivary alpha-glucosidases released glucose, which was then processed by the gustatory system of GA cockroaches as a deterrent and caused the rejection of food. We suggest that the genetic mechanism of glucose-aversion support an extended aversion phenotype that includes glucose-containing oligosaccharides. Salivary digestion protects the cockroach from ingesting toxic chemicals and thus could support the rapid evolution of behavioral and physiological resistance in cockroach populations.
唾液在动物的摄食行为中具有多种功能。然而，唾液对食物的消化作用对昆虫味觉信息处理的影响却鲜有文献记载。德国小蠊的葡萄糖厌恶（GA）是一种高度适应性的可遗传行为抗性特征，可保护蟑螂不摄入含葡萄糖的杀虫剂诱饵。在本研究中，我们证实GA蟑螂会拒绝葡萄糖，但会接受寡糖。然而，虽然接受葡萄糖的野生型蟑螂也会因寡糖而饱腹，但GA蟑螂在几秒钟内就会停止摄取寡糖，导致摄入量显著降低。我们推测唾液可能会水解寡糖，释放出葡萄糖并终止进食。通过将人工收集的蟑螂唾液与各种寡糖混合，我们证明了GA蟑螂对寡糖的厌恶。阿卡波糖，一种α-葡萄糖苷酶抑制剂，可防止葡萄糖的积累，并挽救了对寡糖的摄食刺激反应和摄取。我们的结果表明，唾液中的α-葡萄糖苷酶对寡糖进行口前和口腔水解会释放葡萄糖，然后GA蟑螂的味觉系统将其作为一种威慑物进行处理，并导致对食物的拒绝。我们认为，葡萄糖厌恶的遗传机制支持了一种扩展的厌恶表型，其中包括含葡萄糖的寡糖。唾液消化可保护蟑螂不摄入有毒化学物质，因此可能支持蟑螂种群行为和生理抗性的快速进化。
