The blind cavefish, also known as the “blind cavefish,” have evolved over thousands of years and lost their vision. Some cavefish have developed an inordinate number of taste buds on the head and chin.
In a recent study published in the Nature journal Communications Biology, researchers at the University of Cincinnati have determined when the taste buds start to appear in areas beyond the oral cavity. The study received support from the National Science Foundation.
Blind cavefish evolved in cave ponds in northeastern Mexico and are pale pink and nearly translucent compared to their silvery counterparts that live in surface rivers and streams. Despite the many obvious physical differences, the two fish are considered the same species.
“Regression, such as the loss of eyesight and pigmentation, is a well-studied phenomenon, but the biological bases of constructive features are less well understood,” says the article’s senior author, UC professor, and biologist Joshua Gross, whose laboratory is dedicated to the study of evolution and development of cave-dwelling vertebrates.
“Knowing just how many doors this opened for future research involving taste buds and taste development was a truly rewarding aspect of this research, especially considering how long these fish live,” says co-author Daniel Berning, who earned his master’s degree in biology at UC in 2022, while working on the study in Dr. Gross’ lab.
In the 1960s, scientists made a groundbreaking discovery about blind cavefish possessing additional taste buds on their head and chin. However, this remarkable trait has not been extensively studied to understand its genetic or developmental processes. Dr. Gross and his research team focused on Astyanax mexicanus, particularly two cavefish populations found in the Pachón and Tinaja caves in northwestern Mexico, known for their extra taste buds.
Their research revealed that the number of taste buds remains similar to surface fish from birth up to the age of 5 months. Then, these taste buds gradually increase in number and start appearing on the head and chin during adulthood, particularly at around 18 months of age.
Cavefish have been observed to live well beyond 18 months in both natural and captive environments, leading researchers to believe that their taste buds continue to multiply as they age.
According to Gross, this increase in taste buds coincides with the time when the cavefish transition from consuming other live foods to seeking alternative sources of sustenance, such as bat guano. What’s equally intriguing, he notes, is that this phenomenon may occur in cave locations where there are no bat populations.
With an amplified number of taste buds, the cavefish possess a heightened sense of taste, which is likely an adaptive trait.
“It remains unclear what is the precise functional and adaptive relevance of this augmented taste system,” says Gross, which has led the team to begin new studies that focus on taste by exposing the fish to different flavors such as sour, sweet, and bitter.
Journal reference:
- Daniel Berning, Halle Heerema & Joshua B. Gross. The spatiotemporal and genetic architecture of extraoral taste buds in Astyanax cavefish. Communications Biology, 2024; DOI: 10.1038/s42003-024-06635-2
