Ever Wonder Why Some Fish Have Huge Lips? Here’s the Answer – The Daily Galaxy
2025-04-30T19:30:00Z
Scientists have uncovered the surprising genetic secret behind the massive lips of African cichlids. What they found could revolutionize our understanding of evolution—and even human health.
One feature that has long captured the attention of biologists and aquarists alike is the unusually large lips of some cichlid species.
These thick, plump lips have puzzled researchers for years, leaving them to wonder what drives this curious evolutionary trait.
Recent research, led by Dr. Nagatoshi Machii at the Tokyo Institute of Technology, has now uncovered the genetic and molecular mechanisms behind the cichlid’s oversized lips.
The Mystery of Parallel Evolution
The oversized lips of cichlids are not a random occurrence but rather the result of parallel evolution.
This process refers to the repeated emergence of similar traits in species that are not closely related but share similar environmental pressures.
In the case of cichlids, the isolated ecosystems of lakes Victoria, Malawi, and Tanganyika act as natural laboratories for parallel evolution.
Each lake has its own distinct set of cichlid species, but many of them have developed similar lip structures independently.
As Jonathan Losos, an evolutionary biologist at Harvard, explains, “Parallel evolution is evidence of natural selection that drives adaptive solutions to the environment.”
In this context, the thick lips of cichlids likely evolved as an adaptive response to their underwater environments, where they face unique challenges related to foraging and navigating rocky crevices.
Credit: eLife
The Proteins Behind Plump Lips
Dr. Machii and his team discovered that the large lips of cichlids are rich in proteoglycans, large molecules that consist of proteins and sugar chains.
These molecules play a crucial role in maintaining the structure and integrity of tissues like bone, cartilage, and skin.
Proteoglycans help retain water and give tissues their mechanical properties, which in the case of cichlid lips, contributes to their plump appearance.
The study found that cichlids with oversized lips have a high concentration of chondroitin sulfate proteoglycans.
These molecules promote tissue expansion by attracting and holding large amounts of water, a process that helps increase the volume of the lips.
This discovery sheds light on the molecular foundation behind the cichlid’s unique feature, showing how a combination of proteins and water retention leads to the development of thick, fleshy lips.
Gene Expression and Development
The development of large lips in cichlids begins early in life, as genes responsible for the construction of extracellular matrix components are already active in juvenile fish.
These genes, which help build the connective tissues that make up the lips, are more active in species that will eventually develop larger lips compared to species with normal-sized lips.
This early gene expression suggests that the groundwork for lip hypertrophy, or abnormal growth, is laid during the juvenile stages of life and is reinforced as the fish matures.
The study also revealed that certain genetic pathways, such as the Wnt signaling network, play a key role in this process. The Wnt pathway is a complex network of proteins that regulates various cellular functions, including growth, division, and movement.
It is especially important during embryonic development but also aids in the maintenance of tissues in adult organisms.
Unlikely Connections to Human Health
The same proteoglycans that help cichlid lips expand also play a role in human conditions such as keloids. Keloids are raised, fibrous scars that form when excess connective tissue is produced during the healing process.
This shared biological feature raises intriguing questions about how these molecular processes could apply to human health.
Researchers hope that studying the molecular mechanisms behind cichlid lip growth may provide valuable insights into human connective tissue disorders.
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