Researchers have discovered that antlions have adapted to their ecological niche, leading to changes in their venom composition. They conducted a comparison between the venom systems of antlion larvae and those of closely related green lacewing larvae. Antlions produce a significantly more intricate venom from three distinct venom glands compared to lacewing larvae. Notably, all identified venom proteins originate from the insects themselves, rather than from any symbiotic bacteria. Some of these toxins are novel and seem to be exclusive to antlions. By waiting in sand traps for prey, antlions can effectively use their venom to paralyze larger insects, emphasizing the venom’s crucial ecological function in their desolate habitat.
A recent study published in Communications Biology by researchers from the Max Planck Institute for Chemical Ecology and the University of Giessen highlights how antlions have adapted to their ecological niche, impacting their venom. They compared the venom systems of antlion and related green lacewing larvae, finding that antlions create a more complex venom using three different venom glands. All venom proteins identified are produced by the insects rather than by symbiotic bacteria. Some toxins appear to be new and unique to antlions, which wait in sand “pitfall traps” for their prey, using their venom to immobilize larger victims. As a result, the venom plays a significant role in their adaptation to a harsh environment.
Larvae from net-winged insects, such as those in the green lacewing and antlion families, are predators that utilize venom to capture and digest other arthropods. Green lacewing larvae, known as “aphid lions,” are often employed as beneficial insects in greenhouses because they consume aphids. In contrast, antlions inhabit arid, sandy areas where they construct funnel traps to catch their insect prey. Due to the scarcity of insects in these environments, antlions cannot afford to be choosy. They must overpower and quickly kill even large and resilient prey to survive, requiring potent venom to effectively paralyze their targets and prevent escape.
Complex venom resulting from a system of three distinct glands
The research team, led by Heiko Vogel from the Max Planck Institute for Chemical Ecology and Andreas Vilcinskas from the University of Giessen, aimed to explore the details of antlion venom. They sought to determine the origins of the venom, whether it involves symbiotic bacteria, the organs responsible for its production, its composition, and how the antlion’s venom system and toxicity compare to that of related green lacewing larvae.
“We identified a total of 256 venom proteins in the antlion. The complexity of the venom system is remarkable, with three distinct glands delivering different venoms and digestive enzymes into the prey through the pincers. Antlion venom is considerably more sophisticated and powerful than that of the aphid lion, from which we identified only 137 venom proteins. Our genetic analyses also revealed toxins apparently unique to antlions,” first author Maike Fischer notes.
The team employed various molecular biological, histological, and three-dimensional reconstruction methods to investigate gene expression, protein diversity, and the structure of the venom glands. They also applied HCR-RNA-FISH, a technique combining fluorescence in situ hybridization (FISH) and hybridization chain reaction (HCR), to visualize and measure the distribution and quantity of RNA molecules within individual cells. They demonstrated that three tiny venom glands in the antlion contribute to venom secretion and produce different venom proteins.
Antlions operate independently of bacteria
Fluorescence in situ hybridization analysis to visualize bacteria within the tissue indicated that antlions do not possess symbiotic bacterial partners, a finding that surprised the researchers. “It’s surprising that antlions lack bacteria in their bodies. This is unusual, as most animals host numerous microorganisms, especially in the gut, many of which are vital for survival. We also expected bacteria to be involved in the venom system, as previous assumptions suggested that certain venom proteins were bacteria-derived,” says Martin Kaltenpoth, head of the Department of Insect Symbiosis at the Max Planck Institute for Chemical Ecology.
The unique venom system is a response to the antlion’s ecological niche
Net-winged insects are significant for biological control, especially in greenhouses. However, the evolution and role of venom composition across different net-winged insect species have been largely overlooked. “Our findings reveal that different environments and types of prey significantly influence the venom composition and effectiveness of net-winged insects, potentially impacting predator-prey relationships over time. Antlions create a complex venom mixture that allows them to overpower even large, defensive insects in a low-prey environment. Additionally, they have evolved distinct anatomical structures enabling them to inject either venom or digestive enzymes separately using their mouthparts,” explains Heiko Vogel, head of the “Adaptation and Immunity” project group in the Department of Insect Symbiosis.
Andreas Vilcinskas from the University of Giessen, who leads the “Bioresources” department at the Fraunhofer Institute for Molecular Biology and Applied Ecology (IME), continues to investigate the efficiency and complexity of antlion venom: “Our research confirms that antlion venom is highly effective when delivered into insects. However, we are still uncertain which specific substances contribute to this toxicity. It would be fascinating to determine the roles of various components within this complex venom and how it compares to other insect venoms. The unique toxins found only in antlions are particularly noteworthy,” he says while looking ahead to future studies.
