fish

Unlocking Ancient Cave Histories Through the Eyes of Fish

Conventional methods for dating caves in ​North America face limitations, proving ⁤unreliable for⁤ formations older than 3 to 5​ million years.However, a new study ⁢led by researchers at Yale University and the Max‍ Planck ‍Institute ⁣for Biological Intelligence offers a novel approach, utilizing the evolutionary history ‌of cave-adapted fish‍ to estimate the age of these subterranean‍ environments. The ‍research, published⁤ recently, suggests some⁤ caves may be over 11 million years old – significantly older than previously thought.

The team, co-led by Chase Brownstein of Yale’s Graduate School of Arts and Sciences and Maxime Policarpo of the Max Planck⁣ Institute and University of Basel, focused on amblyopsids, a group of freshwater fish belonging to the ancient Percopsiformes order. By reconstructing a detailed, ‍time-calibrated evolutionary tree using fossil records, ⁣genomic data, ‌and high-resolution scans of living species,​ they were able to ⁣infer minimum cave ages. The logic is‍ straightforward: fish losing their eyesight would only do so within the darkness of a cave,meaning​ the cave must predate the onset of​ this⁢ adaptation.

Interestingly, all cavefish species share similar physical traits – ​elongated bodies, flattened skulls, and reduced or absent⁤ pelvic fins. This morphology is also seen in Cuckoo chologaster, a surface-dwelling “swampfish” closely related to cavefish. While still possessing sight and pigmentation, the swampfish exhibits softening of the bones around the eyes, ⁣hinting that the ancestor of cavefish was already adapted to low-light conditions.

To pinpoint when cavefish began colonizing caves, researchers analyzed‌ the genomes⁢ of these species, specifically examining‍ 88‍ genes related to vision for ⁣mutations. They discovered that different cavefish lineages had⁣ accumulated distinct sets⁤ of genetic ⁤mutations responsible for vision loss. This indicates that multiple species independently colonized caves and adapted to the subterranean habitat, rather than a single event.

From this genomic data, the researchers developed a method to estimate the number of generations as⁤ cavefish began adapting⁢ to cave life by ​losing functional vision genes.​ Their analysis revealed‍ cave adaptations occurred between 2.25 and 11.3 million years ⁤ago in Ozark cavefish, and between 342,000⁣ to 1.70 million years ago (minimum) and 1.7 to 8.7‍ million years ago ​(maximum) for othre lineages. These maximum age estimates surpass the⁣ capabilities of traditional cave-dating techniques like isotope analysis of cosmogenic nuclides.

beyond geological implications, the study also holds‌ potential for medical ​advancements. According to Thomas Near, Yale professor and senior author, ‌mutations‍ causing eye degeneration in cavefish are strikingly⁢ similar to those responsible for ocular diseases in ⁢humans.”Ther is the possibility for translational medicine,” Near explains, ⁤”through which ⁤by studying this ‍natural system in cavefishes, we ‍can glean insights into the genomic mechanisms of eye diseases in humans.”

The research ‌involved collaboration with scientists​ from the South Carolina Department of Natural Resources, ⁣the American Museum of Natural History, Florida State University, and Paris-Cité ‍University. This innovative approach demonstrates the power of evolutionary biology to unlock secrets⁣ hidden within the darkness of ancient caves.