If you’ve ever wondered what to call a fish with no eyes, you’re not alone.
In fact, this phenomenon has a scientific name:
Faceless Cusk. Also known as Mexican Tetra, this fish lacks melanin pigment and is pink in color.
Mexican blind cavefish lack eyes
Astyanax Mexicanus, otherwise known as the Mexican blind cavefish, is one of several species of cavefish.
Its eyes were not developed until adulthood and the fish spends most of its life in darkness.
This is due to a mutation in a gene responsible for eye development.
It has also developed a better mechano-sensory system, allowing it to perceive the environment with vibrations.
During embryonic development, Mexican cavefish develop a rudimentary eye, but the fish undergoes a regressive process.
After 24 hours, eye development stops and the animal begins a process of degeneration that starts with apoptosis of the lens and retina.
When this process completes, the fish’s eyes sink into its orbit and are covered with non-pigmented scales.
The lack of eyes is thought to result from a loss of function of the oca2 gene, which controls the production of melanin.
The result is a silver-gray appearance.
Genetic tests have shown that some albino populations of A. mexicanus have a mutation in the oca2 gene.
Moreover, some of the brownish cave populations display changes in the melanocortin 1 receptor, which is responsible for melanism in mammals and birds.
The visual system in the Mexican tetra is similar to that of other species.
Its small body mass means that the fish must expend substantial energy on maintaining their visual systems.
Since the visual system is crucial to the survival of juveniles, it is probably under strong selection pressure.
It is possible that this is an adaptation to environmental constraints.
The cbsa gene is mutated in blind cavefish. Mutations in this gene cause an accumulation of homocysteine in the eyes, which leads to blindness.
The disease is also associated with hemorrhaging, heart attack, and premature death.
Understanding how this mutation leads to blindness may provide an effective treatment.
Astyanax mexicanus, also known as the Mexican tetra, is a teleost fish from South America.
The first occurrences of this fish in the Characidae family were recorded in the 1930s, and it became available for aquarium use in the US in the 1940s.
A subsequent study by Breder revealed two distinct morphologies in this species.
The species is native to the Sierra de Colmena and Sierra de El Abra regions of Mexico.
A deactivated gene affects the blood supply to the eyes, restricting blood flow to the eye.
This can lead to brain hemorrhages and heart attacks.
This mutation may have occurred in the Mexican tetra as a result of too much energy being expended on maintaining vision.
These findings suggest that eye defects in humans are caused by epigenetic changes.
This process, known as DNA methylation, silences genes through chemical tags called methyl groups.
This is important because it prevents a gene from being expressed.
This is an important step in understanding how eye disease arises.
The study also found that cavefish have asymmetrical skulls, allowing them to see objects in dark caves.
In contrast, most fish have streamlined left and right sides.
It also found that cavefish and Mexican tetras are genetically similar.
Their distant ancestry is thought to have led them to diverge millions of years ago.
Researchers found that the offspring of these surface fish exhibited similar adaptive traits when exposed to darkness.
This suggests that the next generation is better equipped to live in this dark ecosystem because it has increased plasticity in its traits.
They believe that this mutation may have a more long-lasting effect on its overall survival.
Mexican Tetras lack melanin pigment and are pink in color
The Mexican tetra, scientific name Astyanax Mexicanus, is a species of cavefish found in certain rivers in Texas, central Mexico, and eastern Mexico.
These fish are not sighted, but their pattern of behavior makes them difficult to detect without the aid of a binocular microscope.
Researchers have discovered that Mexican tetras have no internal clock.
They lack the pigment that gives their skin color its distinctive color.
They also do not have an internal clock, which helps them conserve energy.
Researchers at the Stowers Institute for Medical Research in Kansas City, Missouri, led a team of evolutionary biologists and researchers to study these peculiar fish.
Scientists studied this phenomenon using the Mexican tetra as a model to learn more about how this fish uses energy.
Their study showed that Mexican tetras use 27 percent less energy than their surface-dwelling counterparts.
This difference in energy consumption is a result of Mexican tetras’ ability to survive in total darkness.