Sydney, Australia - July 15, 2025 A new study has revealed that fish like Nemo from Finding Nemo evolved into different species not just because of where they live, but because of how much they move. Scientists found that some of these colorful reef fish are active travelers, with strong muscles and energy-efficient swimming. Others are stay-at-home types, sticking close to their sea anemone homes and using more energy to swim. For years, experts believed these fish evolved mostly due to their relationship with their sea anemone hosts. But this research shows that how they move, behave, and use energy played a big role in shaping the many types of species we see today. The researchers studied the fish both in the wild and in lab tests. They filmed how much time each fish spent near its anemone and used small water tunnels to test their swimming strength. They also created 3D models to examine their muscles and how their body shape affects movement. The results show that even small differences in behavior and body design can lead to major changes over time — helping explain how new species are born and survive. This discovery helps scientists better understand how animals adapt to their environments, which is especially important as the planet’s climate continues to change.