Satiety and hunger are governed by a network of signals that trace back to ancient biological pathways shared across distant species. Recent work from research groups associated with Tohoku University highlights how hormonal and neuropeptide systems shape feeding behavior in both simple and complex life forms, pointing to deep evolutionary roots for the regulation of intake and energy balance.
The drive to eat, and the sensation of fullness that dampens that drive, emerge from chemical messengers that circulate through the body. Neuropeptides and related hormones act as key switches, influencing appetite in a broad range of organisms, including humans, mice, and fruit flies. The central question is when these signaling systems first appeared during evolution and how they have diversified to support different life strategies. In this context, comparative biology offers a powerful lens for tracing the origins of appetite regulation and how specific signals gained or lost roles over hundreds of millions of years.
To explore these themes, researchers led by Hiromu Tanimoto conducted a comparative study focusing on fruit flies and the jellyfish group, including shell jellyfish. Fruit flies belong to the arthropods, while jellyfish are cnidarians, two lineages that split very early in animal history. The most recent common ancestor of such groups likely lived more than six hundred million years ago, offering a long timeline to study how appetite-control mechanisms evolved. In cnidarians, satiety cues are integrated by cellular regulators such as cladonems, molecules that track food intake and adjust feeding accordingly to prevent overeating in simple, sessile or slow-moving life forms. This line of inquiry helps illuminate how ancient regulatory circuits may be repurposed or conserved across diverse clades.
To map the regulatory landscape, the team compared gene-expression profiles in starved versus fed jellyfish. The state of satiety influenced the activity of a broad set of genes, including those encoding neuropeptides. By synthesizing the candidate neuropeptides and testing their effects, the researchers identified five peptides that consistently reduced food intake in hungry jellyfish, demonstrating that certain hunger-satiety signals can actively limit feeding across a basic nervous system.
Among these signals, GLWamide emerged as a particularly informative molecule. Behavioral analyses showed that GLWamide modulates feeding by halting certain motor programs while enabling the animal to transfer captured prey toward the mouth. In jellyfish, GLWamide’s presence is linked to the base of the tentacles, and its concentration rises as food consumption increases, suggesting a feedback mechanism that helps regulate intake in the short term and coordinate prey processing. This finding provides a tangible link between molecular peptides and the behavioral steps that follow food capture, offering a window into how simple animals optimize energy intake in fluctuating environments.
The study then translated these insights to the fruit fly. In Drosophila, a myoinhibitory peptide (MIP) plays a role analogous to GLWamide, shaping the fly’s eating behavior. Building on the idea of cross-species interchangeability, researchers engineered fruit flies to express GLWamide and jellyfish to express MIP and observed that the introduction of the foreign peptide consistently reduced food intake in both systems. Although the results did not imply a complete interchangeability of signals, they support a shared ancestral lineage for these alimentary regulators and suggest that similar molecular strategies have evolved in parallel to address universal needs for energy management in animals with very different ecologies. The cross-species experiments emphasize how the same core strategy—neurochemical control of appetite—can operate in distinct body plans, reinforcing the view that appetite-regulating circuits have deep, conserved roots in the animal kingdom.
In another note, ancient biologists described how certain moth features act as decoys for predators such as bats, illustrating how evolution can repurpose biological traits to influence ecological interactions. These observations, while not directly tied to current appetite research, highlight the broader theme of how signaling systems and structural adaptations shape survival strategies across species and time.
Taken together, the findings illuminate a continuum of appetite regulation that extends from primitive jellyfish to modern insects and beyond. The identification of GLWamide-like signals in cnidarians and MIP-like signals in insects underscores a shared logic in energy management: signaling molecules respond to nutritional state, adjust feeding actions, and help organisms conserve energy while pursuing nourishment. This line of inquiry not only deepens our understanding of basic biology but also informs broader questions about how feeding regulation evolved to fit the ecological needs of diverse organisms. In the broader scientific context, these results contribute to a growing appreciation for the evolutionary conservation of neuropeptide signaling in controlling appetite and feeding, inviting further investigation into how these ancient pathways continue to shape behavior in contemporary species (citation: Tanimoto et al., evolutionary neurobiology study series).