How do animals see? This has long puzzled science. New developments now shed light on this exciting field. After examining vision data from hundreds of species, researchers from the University of Arkansas in the United States deepen our understanding of how animals perceive colors and what colors they can see. They show how environment and genetic mutations influence vision in vertebrates and invertebrates.
The findings indicate land-dwelling animals tend to perceive a broader color palette than those that live in water. Creatures adapted to open terrestrial habitats detect a wider range of colors than species living in forests or other dense environments.
Evolutionary history, especially differences between vertebrates and invertebrates, strongly shapes the colors a species can see. The study notes that invertebrates tend to detect light at shorter wavelengths compared with vertebrates.
Doctoral student Matt Murphy and assistant professor Erica Westerman published these results in a journal. Proceedings of the Royal Society B: Biological Sciences. The paper, titled Evolutionary history limits species ability to match color sensitivity to available habitat light, explains how environment, evolution and, to some extent, genetic makeup influence how animals see and which colors they perceive.
Eyes of a cat, chirping
“Scientists have long assumed that animal vision evolves to match the colors of light found in their surroundings,” Westerman noted. “But testing this idea is challenging, and there is still much we do not know about animal vision. Collecting data from hundreds of species living in diverse habitats shows that different eye cell types, used to convert light into neural signals, appear invertebrates and vertebrates can use different strategies.”
The secret is in the opsins, the eye proteins.
An animal’s ability to interpret visual information depends on the wavelengths and intensity of light in a given environment. At the same time, the abundance and wavelength sensitivity of a family of retinal proteins called opsins determine the spectrum an animal sees, ranging from near ultraviolet to red light.
However, invertebrates and vertebrates use phylogenetically distinct opsins in their retinas, and the study did not determine whether these differences directly affect what each group sees or how they adapt to light environments.
Eyes of a kind of spider
Murphy and Westerman gathered vision data for 446 species across four groups. One group includes vertebrates with backbones like fish and humans, while the others are invertebrates such as insects, squid, and jellyfish.
Environmental adaptation is not the whole story
The study shows that while animals adjust to their surroundings, their capacity to adapt may be limited by physiology. Vertebrates and invertebrates share many eye cells like opsins, but they build these cells differently. The distinct forms of opsins in vertebrates and invertebrates may help explain why invertebrates excel at short-wavelength vision even when environments favor short-wave light for vertebrates.
Some differences may also come from random genetic mutations that occur in vertebrates but not in invertebrates, according to the researchers. These mutations could constrain the range of light that vertebrate vision can detect.
Much of the mystery behind animal vision remains. Murphy emphasized that the study answers several important questions but also raises new ones. Future work could compare the structure of vertebrate and invertebrate retinas or explore how their brains process visual information differently. These lines of inquiry hold promise for a deeper understanding of visual systems across species.
Reference work: Royal Society Publishing journal, 2022 edition.
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