“Unveiling the Mysteries of the Deep: A Stunning New Scaleless Golden Fish Discovered in Southwest China’s Enigmatic Caves!”
But when did the species become scaleless? Researchers estimate that golden-line fish first entered caves towards the end of the Miocene epoch, roughly 23 million to 5.3 million years ago, when water levels in China started receding.
Xiao M-Y, Wang J-J, Luo T, Zhou J-J, Xiao N, Zhou J/Zoosystematics and EvolutionA preserved specimen of Sinocyclocheilus xingrenensis.
Then, during the Pleistocene epoch, between 2.6 million and 11,700 years ago, the species began losing its scales, pointing to a gradual evolution away from useless physical attributes in its new cave environment — like scales and working eyes. However, other fish species discovered in these caves have already lost both their scales and their eyes, meaning that Sinocyclocheilus xingrenensis may have arrived later in the caves than other golden-line fish.
“This further suggests that most cave fish may not have lived in cave ecosystems for more than a few million years,” the researchers wrote in their study. “Thus, together with the eyes and scales, we hypothesize that the new species may be undergoing a gradual evolutionary process towards caves.”
The Xingren golden-lined fish’s working eyes have also allowed researchers to paint a better picture of its day-to-day life. Unlike the blind fish who swim deep in the darkest recesses of the caves, this species may travel to cave entrances where light is still visible, thereby slowing down its evolutionary process.
“This is related to the habitat, where the new species can be connected to surface streams through cave windows, and their life rhythms may be closely related to [daylight periods],” the study authors wrote.
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