Scientists have discovered that snakes and some other reptiles have completely lost two important genes related to hunger and metabolism. These genes normally help control appetite and energy use in animals.
The researchers examined genetic information from 112 different reptile species, including snakes, turtles, crocodiles, and various lizards. They focused on two specific genes: ghrelin and MBOAT4. Ghrelin is sometimes called the hunger hormone because it helps regulate appetite, food intake, and body weight. The MBOAT4 enzyme works with ghrelin to make it active in the body.
The study found that all 32 snake species examined had lost both genes. Additionally, four chameleon species and two toadhead agama species also lost these genes independently. The researchers looked at the specific DNA sequences where these genes should be located and found clear evidence of mutations that made the genes non-functional.
In animals that still have functional ghrelin, the hormone exists in two forms. During fasting, one form increases while MBOAT4 decreases. After eating, MBOAT4 increases and converts the hormone into its active form, which then triggers appetite signals in the brain. The hormone also helps control how the body stores and uses fat.
The scientists believe this gene loss is connected to the unique eating habits of snakes and these other reptiles. Many snakes can fast for extremely long periods, sometimes lasting months or even over a year. They also have very low energy expenditure when resting between meals. When they do eat, they can consume very large meals and experience dramatic increases in metabolism during digestion.
This research demonstrates how gene loss can be an important evolutionary adaptation. The loss of these genes likely helped these reptiles develop their extreme feeding behaviors and efficient energy use during long fasting periods. The study shows that losing genes is not always harmful and can sometimes provide advantages that help animals survive in their specific environments.