It is unimaginable that any living creature could exist without the use of a brain. The one organ that is mostly responsible for most of our cognitive functioning. It would be impossible for any living creature to effectively exist without a brain to facilitate the coordination and functioning of the body in response to any given stimuli. There are some animals, however, that seem to have defied the rules of nature and gone about their existence without a brain. Some swim through the world’s oceans while others bottom-feed deep down the depths of the oceans; these are some of the known animals that serve their existential purpose in nature yet are literally without a brain.
1. Sea Urchin
First up is the sea urchin. This ocean-dwelling creature roams the ocean floors looking for food without quite knowing what, where, or how to find it. While the sea urchin may not have a plan for hunting for its meals, it doesn’t have much of a problem defending itself. This is because it is quite adequately shielded from predators by lethal spikes protruding from all over its body. Think of it as a rolling ball of needle-like spikes that would certainly puncture the tender insides of any predators’ mouth that would gravely mistake it for a quick meal.
2. Sea Sponge
It is quite remarkable how the sea sponge has managed to be in existence for all this while. Sure being brainless is exceptional, but that doesn’t quite capture the whole essence of what makes the sea sponge genuinely amazing. Besides, it has no internal organs and is made up of some randomly occurring cells that conveniently morph into the particular cell type required at any given time. As if that wasn’t enough, the sea sponge, despite not having any internal organs, is responsive to outside stimuli and will even sneeze if exposed to irritation.
3. Sea Cucumber
Well, much like your regular grocery store cucumber, the sea cucumber doesn’t have a brain. It slithers through the ocean floor with only existence as its purpose. Even though the sea cucumber lacks any gray matter, it reserves some pretty gruesome methods of survival, including abruptly disgorging their entire insides in a heinous and gut-wrenching act of self-defense against what would undoubtedly be displeasure to predators.
4. Sea Star
If there was a prestigious underwater award for the laziest underwater creature, the sea star would probably be among the favorites for the honors. Being brainless isn’t what makes the sea star lazy, just that it will only move when it detects food from either direction of its arms, and will only move towards the said food when it is determined to be there and worth eating. It also has some limited sense of smell, touch, and vision. Huh? Quite a nut-cracker of an animal.
5. Jelly Fish
It is incredible how the jellyfish has been in existence for over five hundred million years, considering it has no brain. As astonishing as it sounds, it would even be weirder if it had one. Because you can see through most species of jellyfish. Jellyfish instead rely on a vast and intricate collection of nerves throughout their skin. The slightest of touches on the skin of a jellyfish would solicit a responsive reaction. They are among the ocean’s oldest dwellers and have proven that existence does not exactly require a brain.
6. Sea Anemones
These plant-like sea creatures belonging to the Actiniaria order are another animal species in existence without a brain. Even though they quite strikingly resemble a plant and grow just as much, they are aquatic animals that grow off of the substrate of rock or sand. It may be even harder to believe their animal status because they have no heart nor brain. What completes their animal nature, however, would be the primitive nervous system that essentially maintains their relevance in the ecosystem.
Otherwise referred to as sea lilies, you would be forgiven if you mistook this sea animal for a plant. Like the sea anemones, the crinoids are characterized by their plant-like physical appearance and have been in existence for a little bit longer than man even walked the earth. Despite not having a brain, crinoids are capable of being aware of their surroundings as well as different stimuli they could inevitably be exposed to.
If there was ever an animal that could offer tales of prehistoric aquatic times, then the Lancetfish would have quite a few of them to tell. Exhibiting primitive evolutionary development, the lancetfish not only has no brain but as well has a poorly developed nervous system and even has no skeleton to protect its internal organs.
It is as mystifying as it is brainless. The Ctenophora is a jellyfish-like sea animal that hasn’t quite been understood. Among the over 200 species known to scientists, some Ctenophora have tentacles while others do not. This highlights their different yet simple bodies without complex organs except for the distributed nervous network around their aquatic bodies that, in turn, allow for stimuli detection or awareness.