1. Jellyfish: Jellyfish lack traditional ears or any specialized auditory organs. They sense vibrations and changes in water pressure through their entire body.
2. Sea Urchins: Sea urchins are echinoderms with a spherical body covered in spines. They do not have any visible ears because they receive sensory information through structures called tube feet and sensory spines distributed across their body.
3. Flatworms: Flatworms, such as planarians, are acoelomate invertebrates that lack ears and have a simplified body organization. They rely on touch-sensitive cells spread across their body to sense their surroundings.
4. Insects like springtails do not have specialized ears like many vertebrates do.
It's important to note that the absence of ears doesn't mean these animals are completely deaf or lack hearing abilities. Many of them have alternative sensory mechanisms that allow them to perceive sound or vibrations in their environment.