When we think of animals, we usually imagine a body with a clearly defined head, complete with eyes, a mouth, and a brain. However, evolution has taken a very different path for some creatures.Several animals either lack a distinct head altogether or have such a diffuse body plan that it is difficult to identify one. Yet many still possess light-sensitive organs or fully developed eyes that help them navigate, detect predators, or find food.Here are five extraordinary examples.StarfishDespite their name, starfish don’t have a true head or brain. Instead, they have radial symmetry, meaning their body is arranged around a central disc.Each arm ends in a tiny eyespot that can detect light, shadows, and large objects. While these eyes cannot form detailed images, they help starfish orient themselves and find their way back to coral reefs after wandering away.Sea urchinsSea urchins also lack a distinct head, but scientists have discovered that they can “see” without having conventional eyes. Their bodies contain numerous light-sensitive cells, and their long spines help block light from different directions, effectively turning the entire body into a simple visual system. This allows sea urchins to detect approaching predators and navigate their surroundings.ScallopsScallops possess one of the most unusual visual systems in the animal kingdom. Instead of having a head, they have up to 200 tiny, bright blue eyes lining the edge of their mantle.Each eye contains a mirror made from microscopic crystals that reflects light onto the retina, a design rarely seen in nature. These eyes help scallops detect movement and escape predators by rapidly clapping their shells together to swim away.Story continues below this adALSO READ | From crows to tigers: Animals that appear to seek revengeMoon jellyfishJellyfish have no brain and no defined head, yet many species possess simple sensory structures called rhopalia. These contain primitive eyes that detect changes in light intensity and direction. Although they cannot see detailed images, these light-sensitive organs help jellyfish maintain their orientation in the water and respond to environmental changes.Brittle starsClose relatives of starfish, brittle stars also lack a distinct head. Instead of relying on eyes located at the ends of their arms, many species have light-sensitive cells embedded throughout their skeleton. This enables them to sense light and shadow across much of their body, helping them quickly retreat into crevices when danger approaches.Explore more captivating stories about pets and animals here, and make us your daily stop for the latest from the animal kingdom.