Department of Biology, The University of Texas Rio Grande Valley, Edinburg, TX, 78539, USA.
School of Earth, Environmental and Marine Sciences, The University of Texas Rio Grande Valley, Edinburg, TX, 78539, USA.
Planta. 2021 Mar 4;253(4):77. doi: 10.1007/s00425-021-03592-6.
The study provides us with the evidence that caterpillars tend to feed on the abaxial leaf surface despite the damage caused to them because of higher trichome density. To defend against herbivory, plants have evolved physical and chemical defense mechanisms, including trichomes (hair like appendages on leaves and stem) being one of them. Caterpillars, a major group of insect herbivores are generally found to occupy the abaxial (underside) leaf surface, considered as an avoidance mechanism from biotic and abiotic stresses. Since trichomes are a first line of defense, we examined the correlation between abaxial vs adaxial (above side) trichomes and caterpillar feeding, behavior, and growth. A combination of field, lab and microscopy experiments were performed using tobacco hornworm, Manduca sexta (Lepidoptera: Sphingidae), a Solanaceae specialist caterpillar, and multiple host species. We found that M. sexta caterpillars overwhelmingly preferred to stay and feed on the abaxial leaf surface, but the abaxial leaf surface also had significantly more trichomes, and consequently, caterpillars took significantly longer to commence feeding. In addition, lab-based diet experiment containing shaved trichomes showed that feeding on the abaxial leaf surface with more trichomes also affected caterpillar growth. Taken together, our study shows that although caterpillars prefer to feed on the abaxial leaf surface, they accrue feeding delays and developmental constraints, indicating tradeoffs affecting performance, and exposure to predation and abiotic stressors.
该研究为我们提供了证据，证明毛毛虫尽管因毛状体密度较高而受到伤害，但仍倾向于取食叶片的下表面。为了防御草食性昆虫的侵害，植物进化出了物理和化学防御机制，其中包括毛状体（叶片和茎上的毛发状附属物）。毛毛虫是昆虫草食性动物的主要群体，通常被发现在叶片的下表面（背面）取食，这被认为是一种避免生物和非生物胁迫的机制。由于毛状体是第一道防线，我们研究了背面与正面（上面）毛状体和毛毛虫取食、行为和生长之间的相关性。使用烟草天蛾（Manduca sexta）（鳞翅目：夜蛾科），一种茄科专食性毛毛虫，以及多种宿主物种，进行了野外、实验室和显微镜实验的组合。我们发现，M. sexta 毛毛虫非常倾向于留在叶片的下表面取食，但下表面的毛状体也明显更多，因此毛毛虫开始取食的时间明显更长。此外，含有刮除毛状体的实验室饮食实验表明，在毛状体较多的下表面取食也会影响毛毛虫的生长。总之，我们的研究表明，尽管毛毛虫更喜欢取食叶片的下表面，但它们会延迟取食并受到发育限制，这表明会对表现产生权衡，增加被捕食和遭受非生物胁迫的风险。
