Leafhopper. Image credit: Larah McElroy (CC BY-NC 2.0)
Animals have evolved various strategies to hide from or escape predators, one of which is camouflage. This adaptation helps animals blend into their surroundings using specific colors or patterns. However, many predators possess multispectral vision, enabling them to detect different wavelengths of light, which can make camouflage based on visible light ineffective.
Insects face substantial predation pressure from visual predators such as birds, reptiles and other arthropods. Many insects dwell in environments with low light reflectivity, such as leaves, tree bark, or soil, and any light reflection from their bodies could increase their visibility.
In response to these selective pressures, many insects have evolved specialized antireflective structures in their cuticle, wings and eyes. For example, leafhoppers have a unique coating on their cuticle known as the brochosome. Brochosomes are hollow, honeycomb-like spheres with a diameter ranging from 0.2 to 0.6 micrometers. They are produced in the excretory system called the Malpighian tubules and are secreted through the hindgut, where they are applied as a coating to the new cuticle after molting.
Brochosomes consist of lipids and proteins, but their exact composition and role remain unclear. Some researchers believe that brochosomes may serve as a protective barrier or antireflective layer. To investigate the camouflage role of brochosomes, Wu et al. used a combination of imaging and gene and protein analyses to study the brochosome coverage and UV reflectance in 5 to 25-day-old male and female leafhoppers of the Cicadellidae family.
The results indicated that older individuals had fewer brochosomes than younger ones. The experiments also revealed that brochosomes significantly reduced the reflection of ultraviolet light from the surface of leafhoppers by around 30% and diminished the reflectance of visible and infrared light.
Next, Wu et al. conducted predation experiments using jumping spiders known to prey on leafhoppers by analyzing the time of the first attack and the feeding behavior of the spider. The findings showed that jumping spiders preferred to attack older individuals with less brochosome coverage. This suggests that brochosomes are particularly beneficial for younger leafhoppers.
Gene and protein analyses identified four structural brochosome proteins. Experimentally blocking these proteins induced changes to the morphology of the brochosomes and modified the characteristics of the leafhoppers’ cuticle, including an increased diameter and structural deformation of the honeycomb architecture, alongside elevated UV reflectance. Phylogenetic analysis of the corresponding genes revealed that these proteins likely evolved through gene duplication events followed by a gradual accumulation of genetic modifications.
The study of Wu et al. demonstrates that brochosomes serve as an antireflective camouflage coating in leafhoppers to evade visual predators. The unique structure and composition of the lipids and proteins making up the brochosomes appear to be responsible for the antireflective properties of this coating. Further studies will advance our understanding of insect antipredator adaptations and evolutionary mechanisms underlying ecological niche specialization. Furthermore, they may provide biomimetic insights relevant for developing advanced camouflage technologies by emulating biological nanostructures such as brochosomes.
