Natures wonders: whale series; how they see (Introduction)

by David Turell , Friday, July 29, 2022, 17:34 (846 days ago) @ David Turell

Study of adaptive whale eyes to see in deep dark waters when deep diving:

https://phys.org/news/2022-07-whales-eyes-glimpse-evolution-sea.html

"Their findings show that the common ancestor of living whales was already a deep diver, able to see in the blue twilight zone of the ocean, with eyes that swiftly adjusted to dim conditions as the whale rushed down on a deep breath of surface air.

"'In the evolution of whale diving, there's been a long-standing question of when deep-sea foraging evolved," says Belinda Chang, a professor in the Faculty of Arts & Science's departments of ecology and evolutionary biology, and cell and systems biology. "And it seems that based on our data, this happened before toothed and baleen whales diverged. The common ancestor of all living cetaceans was deeper diving—and then later species evolved all the diverse foraging specializations we see in modern whales and dolphins today."

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"Whales evolved from mammals that share a common ancestor with hippos and that were partially aquatic. The great mystery of their transition to deep-sea foraging was how quickly this ability developed. Dungan and Chang looked at whale fossils on a molecular level and focused on the rhodopsin protein, which absorbs light and sends a signal that travels through the retina to the brain.

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"'One of the most intriguing aspects of this iconic land-to-sea evolutionary transition is that the qualities of the visual environment completely changed," says Chang. "This helped to define which genes would be the most interesting for us to target in our studies."

"'The fossil record is the gold standard for understanding evolutionary biology," says Dungan. "But despite what Jurassic Park would have you believe, extracting DNA from fossil specimens is rare because the condition tends to be poor. So, if you're interested in how genes and DNA are evolving, you rely on mathematical modeling and a strong sample of genes from living organisms to complement what we understand from the fossil record."

"Dungan and Chang were astonished by the biochemical properties of the resurrected protein compared to land mammals. Early whale rhodopsin was more sensitive to the blue light that penetrates deepest into the ocean, to a degree that exceeded expectations. Its biochemical properties also suggested that the retinas of early whales could respond rapidly to changes in light levels."

Comment: since a very early ancestor of modern whales had a special set of genes to allow for the necessary type of rhodopsin for the specialized vision for deep diving, I find it as more evidence of design for future use