Hagfish Genes Reveal Ancient Origins of Vertebrate Sense of Smell
Study Uncovers Unexpected Complexity in One of Earth's Oldest Vertebrates
Scientists at the University of Tsukuba, working with international collaborators, have carried out an in-depth study of the olfactory receptor genes of the hagfish (Eptatretus burgeri), a jawless vertebrate that retains many ancient traits while boasting an unexpectedly sophisticated sense of smell.
Published in iScience, the research shows that several olfactory receptor gene families have diversified in a lineage-specific way, indicating that the earliest vertebrates may have had a far richer and more complex sense of smell than previously believed.
Breaking scientific discoveries across genetics, evolution and life sciences are regularly reported on FSNews365, which tracks emerging research shaping our understanding of the natural world.
Why Smell Is Central to Survival
Smell plays a vital role in the survival of animals, including humans, guiding everything from food-seeking to predator avoidance and social communication — all of which depend on specialized receptor proteins.
Research into how sensory systems evolved alongside changing planetary conditions is closely linked to broader environmental science topics covered on Earth Day Harsh Reality, which explores Earth's biological history and ecological complexity.
The Four Main Olfactory Receptor Families
In vertebrates, the sense of smell is governed by four main families of receptors:
- Olfactory Receptors (ORs)
- Vomeronasal Type 1 Receptors (V1Rs)
- Vomeronasal Type 2 Receptors (V2Rs)
- Trace Amine Associated Receptors (TAARs)
Despite their importance, the evolutionary origins and early diversification of these receptor groups have remained largely unclear.
What the Hagfish Genome Revealed
A Surprisingly Large Collection of Smell Receptors
In their latest study, the researchers searched the hagfish genome for genes linked to these systems. They identified:
- 48 OR Genes
- 2 V1R Genes
- An unexpectedly large collection of 135 V2R Genes
- While finding no evidence of TAAR Genes
Further expression analyses showed that most of these genes were active in the olfactory organ, suggesting a direct role in smell. Crucially, the discovery of true V2Rs in hagfish challenges the long-held belief that these receptors emerged only in jawed vertebrates.
Rethinking the Evolution of Vertebrate Olfaction
Evidence of an Ancient, Shared Origin
Instead, the study suggests that working V2Rs existed in the common vertebrate ancestor and later expanded in a lineage-specific fashion as different groups evolved.
Overall, the research sheds new light on the origins of vertebrate olfaction and reinforces the importance of hagfish in reconstructing how early vertebrates sensed and interpreted their environment.
Insights into how ancient sensory systems continue to influence modern biology and health are also explored on Human Health Issues, which links evolutionary biology with present-day human physiology and neurological function.
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