This video is called Astyanax mexicanus.
Blind Cave Fish Traded Eyesight for Energy
Sep 14, 2015 04:55 PM ET // by Danny Clemens
At first glance, the blind cave fish is an example of evolution seemingly moving backward.
Over time, a handful of Mexican tetra (Astyanax mexicanus) living at deep depths have gradually lost not only their eyesight, but also their eyes, while their surface-dwelling counterparts have maintained their vision. Dubbed the “blind cave fish”, the eyeless creature also lost much of its pigmentation, growing to sport a body of fleshy pink scales.
According to new research out of Sweden’s Lund University, however, the blind cave fish’s lost vision is actually a major step forward in adapting the fish to its new environment.
Researchers conclude that a highly developed visual system can suck up to 15% of an animal’s “total energy budget”. For a fish living at deep, dark depths with an irregular food supply, that expenditure simply isn’t worth it.
“This is a tremendously high cost! Over evolution, this morph lost both eyes and visual cortex, without a doubt because of the unsustainable energy cost of maintaining a sensory system that no longer had any significance”, study lead author Damian Moran explains in a news release.
Instead, the blind cave fish has come to rely upon a finely tuned sense of smell and a keen sensitivity to changes in water pressure.
Scientists revealed last year that the fish has also ditched its circadian rhythm as an energy-saving measure.
“These cave fish are living in an environment without light, without the circadian presence of food or predators, they’ve got nothing to get ready for, so it looks like they’ve just chopped away this increase in anticipation for the day,” Plant and Food Research New Zealand scientist Dr. Damian Moran explained when his research was published.
The reduction of traits over time is known as “regressive evolution”, according to a 2007 study from New York University.
Mexican cavefish have insulin resistance, a hallmark of many human metabolic disorders and a precursor to type 2 diabetes that can lead to an overworked pancreas, excess fat storage and chronically elevated blood sugar. Despite dysregulated blood sugar, the fish don’t suffer the same health consequences people do. Study offers a fresh opportunity to understand how animals thrive with traits that sicken humans and could point the way to new interventions for disease: here.
Sleepless in Latin America: Blind cavefish, extreme environments and insomnia. Study provides first genetic insight into evolution of sleep loss in Mexican cave-dwelling fish: here.
Loss of eye tissue in blind cavefish (Astyanax mexicanus), which occurs within a few days of their development, happens through epigenetic silencing of eye-related genes, according to a new study. Epigenetic regulation is a process where genes are turned off or on, typically in a reversible or temporary manner. This mechanism differs from genetic mutations, which are permanent changes in the DNA code: here.
Researchers have discovered the first European cave fish. A hobby cave diver first sighted the fish, a loach in the genus Barbatula, living in a hard-to-reach, underground water system in South Germany: here.
Scientists are studying a guppy-sized, blind, translucent fish that lives in the cave systems of northern Mexico to figure out why some animals can regenerate their hearts, while others just scar. Their research appears November 20 in the journal Cell Reports. “Millions of years ago, some surface fish living in rivers flooded into caves, became trapped when river levels retreated, and lost their eyes and pigment to adapt to cave life,” says co-senior author Mathilda Mommersteeg, developmental scientist at the University of Oxford. “We have discovered that, like zebrafish, the river surface fish regenerate their heart, while some cavefish cannot and form a permanent scar. We introduce the Mexican cavefish as a new model for heart regeneration research”: here.