What We Can Learn From an Insomniac Fish.

The Mexican tetra, a blind cavefish, has intrigued scientists with its unique sleep patterns. Despite living in darkness, these fish sleep for short, random periods totaling about three and a half hours each day. Researchers have discovered that the fish have an excess of cells that produce a neurotransmitter called hypocretin, which promotes wakefulness. The fish's lack of external cues, known as zeitgebers, is believed to be the reason for their irregular sleep. This research provides insight into the complex relationship between sleep and circadian rhythms, and how they can be influenced by evolution. In 1938, a study conducted in a cave in Kentucky found that humans' sleep patterns shifted to a 28-hour day in the absence of routine cues. However, other experiments have shown that most people still maintain a close-to-24-hour sleep cycle, suggesting the influence of circadian rhythms. Humans are adaptable and could potentially develop new sleep patterns in different environments over time. The study of sleep variations in nature is crucial for understanding its potential and the reasons behind different sleep patterns. [Extracted from the article]