Deep diving whales turned to the sea 35 million years ago from land with a key adaptation from a long-lost ancestor that was able to see in the dark depths.
Modern cetaceans can see underwater, dive deep, or hunt for prey when the sun's light cannot be seen in ocean depths. This adaptation is present in modern whales, dolphins, and porpoises with excellent underwater vision.
Deep Sea Vision Developed From Early Ancestors
Whales and hippos, which appear unrelated, share a 50-million-year-old quadruped terrestrial mammal as their common ancestor. They live in water but have only one evolved the ability to plump the aquatic depths of any known mammal, reported Science Alert.
Speculation about how that trait evolved is still unknown, but new research shows deep-sea vision happened very early in the evolution of whales as they took to the sea.
The findings are based on rhodopsin, a protein found in mammalian eyes that is especially sensitive to dim blue light like that seen in the deep ocean.
Researchers were able to figure out the ancestral genetic code that first enabled deep underwater dives by investigating the genes behind such a protein in live whales and certain similar mammals.
Lab experiments were able to reproduce these cells, and the distinct genetic sequence was able to dig up this long-lost pigment protein.
This protein is far more sensitive to low light levels than terrestrial mammals. It also reacts quickly to variations in light intensity. Deep diving whales have this ability from a long-lost ancestor at the start of cetacean evolution.
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Vision Adaptation for Deep Sea Diving
Developing a protein capable of deep-water vision in the first cetacean that could have dove roughly 650 feet deep; when the sea depths darkened with just enough light, noted NOAA.
According to the authors, these ancestral changes in rhodopsin function suggest that the first fully aquatic cetaceans may have dived into the mesopelagic zone.
Findings say it was already present before whales evolved into toothed or baleen whales. Instead, it seems that all whales and dolphins, including those who presently hunt in shallow seas, evolved from an ancestor who could see in the deep.
Belinda Chang, an evolutionary biologist from the University of Toronto, claimed that species had evolved all of the diverse foraging specializations shown in modern whales and dolphins.
Early investigations of fossils suggest that the first aquatic cetaceans had dolphin-like anatomy with tail fins and leftover limbs for swimming. This is one of the first studies to investigate the workings of whale vision, which evolved early in the species to hunt for food in the deep pelagic water millions of years ago.
According to Sarah Dungan, an evolutionary biologist at the University of Toronto, the fossil record is the gold standard for understanding evolutionary biology. Nevertheless, due to their poor preservation, retrieving DNA from fossil material is hard, in contrast to popular perception.
Mathematical models and good DNA sources are used to back up a hypothesis, as mentioned in PNAS.
Deep diving whales had long-lost ancestors that evolved rhodopsin in their eyes to compete for new food sources in the maritime sea.
