In what could be a first in the world, a fish species in the cichlid family has been observed by scientists in the act of splitting into two distinct species in Lake Victoria, Africa’s largest lake and one of the world’s biggest fresh water bodies.
This may be remarkable because what is causing them to diverge are adaptations to their vision as animals and plants try to cope with increased pollution and the effects of climate change. The change is also happening without geographical isolation, which was thought to be a precursor for evolution.
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The Pundamilia nyererei is a haplochromine type cichlid native to areas in the Mwanza Gulf region of Lake Victoria. This region consists of many islands where each island region has its own color variant of the fish.
In a report published in the journal Nature, researchers from Tokyo’s Institute of Technology and the Swiss Federal Institute of Aquatic Science and Technology have observed the cichlid evolve into a new species better adapted in sighting its prey and predator.
But the scientists have also tabled evidence indicating that it is not pollution and over-fishing alone that are responsible for the disappearance of some fish species in Lake Victoria and the evolving of others like the cichlid into new species.
The report summarizes that new species may be born because of vision differences and what fish see at least in one African lake could be the driving force that causes them to evolve into new species.
This may explain the very rapid loss of pundamilia in Lake Victoria over the past 30 years. The study says the eye adaptations have also affected mating patterns.
Researchers looked at two species, conspicuous by their red or blue colours. They determined through lab experiments that certain genetic mutations helped some fish adapt their vision at deeper levels to see the colour red and others in shallower water to recognise shades of blue.
The researchers showed that the eyes have adapted to this difference so that fish that live in deeper water have a pigment in their eyes that is more sensitive to red light, while shallow-water fish were sensitive to blue.
Generally, the evolutionary process of speciation (the formation of new species) occurs when one species is split by a physical distance or barrier, allowing each group to develop different traits. The observations of Lake Victoria’s cichlids provide evidence of an unusual form of evolution known as sympatric speciation, which occurs without the physical separation of a population group.
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Image credit: Erica Marshall at Flickr under a Creative Commons license.