How did mammals evolve to live in the sea?

Introduction Did you know that cetaceans (whales, dolphins and marsopas) are mammals? About 50 million years ago, their ancestors lived on land. They later evolved to live in marine environments. An extreme habitat transition required many adaptations. A remarkable example is how cetaceans sleep: half of your brain rests, while the other half remains active! This unihemispheric dream ensures that cetaceans are always taking care of predators and food. Other adaptations helped cetaceans to hunt their prey under water. For example, the reduction of oxygen demands allowed them to dive for longer and control their blood pressure at great depths. The thick layers of fat also helped isolate them from cold waters. There are many molecules that control physiological features such as sleeping, blood pressure and temperature control. Among them, neuropeptides are especially important. Neuropeptides are chemical messengers. They relay the signs from one nerve cell to another, triggering a physiological change. They can also have more than one paper in the body. Fortunately, neuropeptides are found in all mammals. We wanted to know how these neuropeptides changed as mammals evolved. This information can help us understand how mammals adapted to living in the ocean. Methods Step 1: Identification of important neuropeptides We identify 12 neuropeptides. Previous investigations have shown that they can be related to important features in cetaceans. Step 2: Obtain DNA sequences for each neuropeptide are microscopic, so it is difficult to detect differences between them. An easy way to compare neuropeptides is to look at their DNA sequences. DNA is like an instruction manual. A specific sequence can build a specific molecule (in this case, a neuropeptide). We obtained the DNA sequences for our online database neuropeptides. We did this for 202 different mammals species. This included 41 species of cetaceans. Step 3: Comparing the ability to create neuropeptides, we use a computer program to “build” neuropeptides depending on their DNA sequences. The computer program gave each DNA sequence a score from 0 to 5. A score of 0 meant that the neuropeptide would work. (Think about it as zero problems!). A score between 2 and 5 meant that the neuropeptide would not work. Then we compare the scores for each of the 12 neuropeptides in cetaceans and terrestrial mammals. RESULTS It turns out that cetaceans have lost the ability to make many of the neuropeptides found in terrestrial mammals. We discovered that many cetacean neuropeptides had scores greater than 2. The cetaceans also had less DNA sequences that made functional neuropeptides than any other group of mammals. For example, neuropeptide B helps mammals to sleep and suppress hunger. Most cetaceans do not have the correct DNA sequence to build neuropeptide B (Figure 1). There were some DNA sequences that created neuropeptides that worked. For example, cetaceans still produce neuropeptide Y. This controls blood pressure, fat storage and sleep. Discussion Why would cetaceans have lost the ability to make many of the neuropeptides that terrestrial mammals still have? Over time, DNA can collect mutations. Sometimes, these mutations create new features that are beneficial. Sometimes they do nothing. But on other occasions you can spoil the instructions that DNA carries. This means that whatever the DNA sequence will not work properly. This is probably what happened to these neuropeptides. The ancestors of modern cetaceans probably did not need many of those neuropeptides in their new marine environment. Then, when the DNA mutated, it didn’t matter. They may have even benefited from losing the ability to make specific neuropeptides. For example, they may have lost the ability to make neuropeptide B (which suppresses hunger and induces sleep). This allowed cetaceans to eat a lot of food and keep half of their brain awake. Fortunately, most neuropeptides have more than one paper. Therefore, cetaceans did not completely lose the ability to sleep or regulate their appetite. The evolution of terrestrial mammals cetaceans is complex. But it is clear that the loss of work neuropeptides played a role. His loss allowed early cetaceans to prosper in a marine habitat. Conclusion Understanding how cetaceans have adapted to the marine world could help us understand how other mammals have evolved in their new environments. After all, the transition from Earth to water is not the only important change of habitat that mammals have suffered. For example, the bats made the transition to climb the trees to fly. Unfortunately, many animals and plants face the loss of habitat. Discover local plants and animals in your area and how can you help protect them!