This blog post explores the principles, functions, and ecological significance of pheromones, which play a crucial role in the survival and social organization of living organisms.
Survival of the fittest is the survival method acknowledged by all living organisms in nature. To survive the competition for survival, each organism has developed various strategies. Among these, one of the most important strategies is communication. From viruses to whales, regardless of size, organisms have evolved diverse communication methods—such as vocalizations, body language, and chemical substances—which are vital for adapting to and surviving in their environments. These communication methods are themselves products of biological evolution, enabling organisms to interact and form complex ecosystems.
Communication methods constitute the most fundamental yet crucial aspect of an organism’s survival strategy. For example, interactions occur where predators locate prey, and prey detect the predator’s approach and flee. This communication plays a vital role, enabling organisms to go beyond mere survival to reproduce, form social structures, and maintain groups.
Among these, communication via chemical substances is thought to best demonstrate biological evolution, as it occurs innately without needing to be learned. Chemicals serve as essential tools for organisms to adapt to complex environments, regulating not only inter-individual communication but also physiological processes within individuals. Pheromones are a prime example of such chemicals, exerting powerful influence in many contexts.
Pheromones are substances used as a means of communication between individuals, influencing group activities such as sexual behavior, aggregation, and warning signals within a specific species. They differ from hormones, which govern life activities within an individual, in that they are biological substances affecting collective activities among individuals of the same species. The first form of pheromones is the ‘releaser,’ which acts through olfactory receptors to immediately trigger behavior, while the second form is the ‘primer,’ which is activated orally and induces longer-term physiological changes. These diverse functions of pheromones play a significant role in the physiological and behavioral adaptations of organisms.
The primer effect refers to the case where an individual receiving a pheromone undergoes a series of physiological changes. These changes begin as the pheromone is absorbed into the body through the taste organs. In social insects like bees and ants, these pheromones induce complex physiological changes such as caste differentiation and suppression of reproductive capacity. These changes not only alter the physiological state of the individual but are also essential for maintaining the structure of the entire colony. Therefore, primer effect pheromones transcend the role of simple signaling molecules, playing a crucial role in the social organization of organisms and within ecosystems.
Take ants as an example. Queen ants and worker ants are born from biologically identical eggs but undergo different differentiation processes during growth. Worker ants, who spend their entire lives gathering food for the queen and performing labor before dying, are effectively females whose reproductive structures remain undeveloped. As this example illustrates, physiological change pheromones induce specific physiological alterations, enabling the maintenance of caste hierarchy within ant colonies. This is a crucial example demonstrating how a group’s social structure can be formed and sustained through chemical signals, even without physical differences between individuals.
In contrast, the emission effect refers to cases where the pheromone immediately alters the behavior of the receiving individual. Such pheromones are also called behavioral pheromones, serving as a guidebook for the actions individuals should perform next. That is, they induce various behaviors such as mating stimulation, inhibition, and sexual attraction, as well as pathfinding, enabling immediate survival responses in specific environments.
For example, upon suddenly encountering a predator, they disperse alarm pheromones to trigger vigilance in nearby conspecifics, or use aggregation and dispersion pheromones to signal the location of prey. These behavioral pheromones induce rapid collective responses in specific situations, enabling the survival and prosperity of the species. The ichneumon fly is a prime example. This insect must lay its eggs on the larvae of other insects, a task that carries the risk of threatening its own survival. However, the ichneumon fly employs a strategy to survive within ant nests using pheromones. It cleverly uses attractant pheromones and aggression-inducing pheromones to provoke civil war among the ants.
Beyond this, the roles of pheromones are extremely diverse. Living organisms use these chemicals to preserve their species and maintain ecosystems. Humans, too, have grasped the principles of these pheromones and applied them in various fields such as agriculture, pest control, and animal breeding management. It is hoped that research on pheromones will become more active in the future, enabling a deeper understanding of nature’s secrets and their practical application.
Pheromones do not merely regulate physiological responses in animals; they play a crucial role in maintaining the balance of entire ecosystems. Therefore, understanding pheromones remains one of the key challenges in life sciences, offering humanity the opportunity to explore the complexity and mysteries of nature more profoundly.
