Blind cavefish lost their eyes, but gained taste buds on their head

Have you ever stopped to taste the water while swimming in a river? Now, imagine being a blind cavefish with an incredible multitude of taste buds scattered all over your head and chin. Makes you wonder what these peculiar creatures are tasting, right? Well, that’s precisely what the researchers at the University of Cincinnati have been trying to figure out.

In a recent article published in the Nature journal Communications Biology, these scientists embarked on an intriguing journey to discover when and why these extra taste buds appear in places beyond the confines of the mouth.

The research, supported by the National Science Foundation, delves deeply into the evolution of the humble cavefish.

The tale of blind cavefish

Blind cavefish took evolution in stride, adapting to dark, subterranean life by losing their eyes but gaining a fascinating attribute in return – an abundance of taste buds.

These translucent, pink inhabitants of cave ponds in northeastern Mexico have a distinct difference from their silvery relatives residing in surface rivers and streams – those extra taste buds.

While the surface fish showcase massive round eyes that seem to suggest a sense of constant surprise, our star, the cavefish, boasts a faint outline of what used to be eye sockets.

Interestingly, despite the glaring physical disparities, both types of fish are considered the same species. 

Cavefish taste buds

“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,” said UC professor and biologist Joshua Gross, the study’s senior author.

Gross, an expert in evolution and development of cave-dwelling vertebrates, takes us further into the mystery of the blind cavefish’s peculiar gift. 

He explains that while some scientists in the 1960s stumbled upon the fact that certain blind cavefish populations had extra taste buds, no extensive studies were conducted to understand the development or genetic processes behind this unique trait.

Flavor-filled findings

To unveil the truth behind the blind cavefish’s plentiful taste buds, Gross and his team studied two separate cavefish populations living in the Pachón and Tinaja caves in northwestern Mexico. The results were surprising and enlightening at the same time.

The team discovered that the cavefish and their surface-dwelling counterparts had a similar number of taste buds from birth until about five months of age. Then things began to change.

The cavefish started to grow extra taste buds on their heads and chins, a trend that continued well into their adulthood, around the 18-month mark. But why this sudden eruption of taste buds, and what purpose did they serve?

New perspective on cavefish taste

Gross speculates that this increase coincides with a shift in the cavefish’s diet. They stop relying on traditional food sources and start eating, believe it or not, bat guano. However, the most exciting part is that this expansion continues even in caves devoid of bats.

The abundance of taste buds enhances the cavefish’s sense of taste, giving them an adaptive edge in their dark dwellings. 

“It remains unclear what is the precise functional and adaptive relevance of this augmented taste system,” noted Professor Gross. This uncertainty paves the path for more exploration.

The researchers are now set to investigate further, planning to expose the cavefish to a variety of flavors – sweet, sour, and bitter – to better understand this miraculous gift of taste.

Significance of the study

The tale of the blind cavefish continues to captivate our imagination. Their remarkable evolution and adaptation to an environment that is completely alien to us showcase the incredible resilience of life.

These unique creatures remind us of nature’s wonders and the perplexing mysteries that still await discovery, urging us to explore deeper into the unknown. Each new finding about their behavior and habitat reveals more about the complexity of life on Earth and the intricate connections that bind all living things.

So, next time you take a dip in a river or simply sip a glass of water, spare a thought for our little blind cavefish and their extraordinary tasting abilities. After all, not everyone need eyes to lead an interesting life, some just need extra taste buds.

The study is published in the journal Communications Biology.

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