Red starfish in blue ocean water Red starfish in blue ocean water

Are there Animals Surviving Without Brains? Exploring Nature’s Simplest Creatures

Aren’t you curious about how animals work just like us? How do you know if an organism is actually an animal? Well, this time, I found some exciting and jaw-dropping facts about the brainless wonders of the world. Wait. I’m talking about animals with no brains. I always heard that all things need brains to live. It may sound unimaginable but, some animals do not have any brains, yet they survive just fine!

Now, when we see different animals, some have one brain, some have no brain, and some even have multiple brains, and this article is all about knowing the animal brains. I’m sure it almost feels impossible to imagine a living being other than plants that can actually live and thrive without a brain. Plus, compared to plants, animals are quite complex. Even then some animals do not have a brain.

what animals don't have brains
– Source: Pixabay

1. Starfish

Starfish is an invertebrate and belongs to the Asteroida order. It lives in the deep sea and can have anywhere between five to fifty arms, depending upon the species. The arms are their life literally as they help them to reproduce, excrete, and hunt.

Along with brains, they also do not have hearts. In addition to these, they have extremely brilliant nervous systems, which are formed by the nervous plexus.

what animals don't have brains
– Source: Pixabay

These send signals to the different parts of the body and work as a distributed brain, which helps them to take in stimuli and produce a reaction accordingly.

2. Sea Cucumber

Sea cucumbers have a very functional oral cavity in place of the brain that actually functions like one. As is it surrounded by the neural tissue which helps in sending signals to the mouth and testicles.

To feed themselves, they move on the seafloor, looking for food like algae and other decomposing material.

what animals don't have brains
– Source: Pixabay

Due to the way that they consume food, it is highly likely for them to actually eat some mud and sand, which is then filtered out of their food like a sieve. Usually, animals like turtles, crabs, and fishes eat sea cucumbers.

3. Jellyfish

Jellyfish are translucent, and they are unique animals that do not have brains. They are immobile and usually live in one spot throughout their lives. They move with the help of ocean currents and squirt water for forward movement. This ability to squirt water helps them to move away from predators.

They also have tentacles which serve as the main protection feature as they are capable of releasing toxic substances that can even kill their predators. All these actions are functioning with the help of a network of sensory nerves.

what animals don't have brains
– Source: Pixabay

In an interview with the Icy Whiz team, Billy Litmer, Founder of Honest Eco Tours, talked about this unique phenomenon. Here is what he said:

Billy Litmer - Featured
Billy Litmer

As a biologist and advocate for marine ecology, I have a deep interest in sustainable marine life. It’s quite intriguing to observe that some animals live without brains. For instance, consider how jellyfish dominate the seas without a brain.

The interesting aspect of animals without brains is that their simple structure represents an impressive evolutionary adaptation.

Many of them, like jellyfish, have endured through every mass extinction event, while most species that ever lived have perished. These “bags of water” have remarkably survived for over 600 million years.

Additionally, it appears that brains are not necessary for thinking and problem-solving—simple cells are capable of these functions. Small clusters of cells demonstrate basic cognitive functions, and some animals can retain memories even after decapitation.

Intelligence is essentially a collective phenomenon, as every cognitive system comprises various parts. It has been discovered that ordinary cells—not just specialized brain cells like neurons—can store information and respond based on it.

Research in this exciting field has revealed signs of intelligence, such as learning, memory, and problem-solving capabilities, both outside of and within brains.”

4. Corals

You will be surprised to know that corals not only have no brains but also they have no nervous system or heart. Their structural formation is such that it consists of thousands of polyps that have tentacles and these have nerve endings.

Corals, when they form reefs, actually look like formations of rock or some plants and sometimes even like they are non-living beings.

what animals don't have brains
– Source: Pixabay

They are of a variety of types and usually live in colonies. The polyps are what help these organisms to catch prey and understand their surrounding environment.

5. Sea Sponges

Another strikingly surprising creature is sea sponges; these also have no brains plus no internal organs. Since they are immobile, they eat the tiny organisms and other particles around the water they are in after being filtered.

what animals don't have brains
– Source: Pixabay

They have an extremely long life, and some sea schools claim that they can live for more than 100 years. In total, there are more than 8000 species of sea sponges, and they are different in terms of fresh water and salty water.

6. Sea Anemones

Sea anemones have no brain, no heart, and no organs. They are like coral and sometimes resemble plants, but they live and actually grow by attaching themselves to a rock or sand substrate.

They have a very basic and primitive nervous system that helps them to react to the stimuli that they receive. It also helps these creatures in maintaining their vital balance.

what animals don't have brains
– Source: Pixabay

Like other sea animals, they also have tentacles with stinging properties to protect themselves from predators.

7. Clams

Clams belong to the same family as oysters and scallops. They can open and close their shells.

These are mollusks which have a compressed body inside a shell. They have almost everything but a brain like stomach, heart, mouth, kidneys, and even a nervous system.

what animals don't have brains
– Source: Pixabay

They are bivalve and, hence, can survive in both salt water and fresh water. Their nervous system is pretty strong, and it helps them to feel things and react to them. They are very popular across the globe as they are found literally everywhere.

We interviewed Daniel Conley, PhD Candidate at Scripps Institution of Oceanography, and asked him about the remarkable abilities of animals without brains to survive and thrive in their respective environments. Since he is a scholar, he brought valuable insights to this topic. Here is what he said:

Daniel Conley
Daniel Conley

“Animals without brains, such as corals, jellyfish, and sea cucumbers, showcase an incredible array of survival strategies that challenge our traditional views of nervous system necessity.

Their existence and thriving demonstrate that complex behaviors and adaptations can evolve in the absence of centralized nervous systems. 

For instance, corals, which are brainless, can form vast reef ecosystems that are vital to marine biodiversity. These organisms rely on a sophisticated interplay of genetic, chemical, and physical cues to communicate, reproduce, and adapt to their surroundings. 

The understanding of how these animals have evolved to survive and flourish helps us expand our perspective on the mechanisms of life, highlighting the versatility and resilience of biological systems.

Their adaptations contribute significantly to our understanding of evolutionary biology by expanding the scope of what is considered possible in the natural world, offering valuable insights into the diversity of life on Earth.”

Isn’t It Amazing That There Are Creatures on This Planet Who Live Without Brains?

Humans rely a lot on the brain and tend to use it everywhere. While animals like jellyfish, coral, and starfish don’t require brains. They have some sort of specialized cells that may allow them to respond and sense the environment. To help them navigate the world, some animals have simple nervous systems that have no centralized brain.

Usually, animals that do not have brains are aquatic, and the underlying reason is their morphology, which they acquired from their ancestors. But how do they actually survive? So, to understand this, we have to first keep in mind that all animals adapt to their lives and ecosystems. They figure out ways to exist, eat, reproduce, and excrete.

The key to survival is basically the removal of all the complex parts of the body, which require a lot of brain usage; so, simplicity is what allows them to survive without a brain.

Guest Author: Saket Kumar

Last Updated on May 19, 2024 by Pragya


Anushree Khandelwal
  1. The facts about the animals that doesn’t have brain is very interesting as we have learned that brains control every body part. It’s really extraordinary how well those animals perform their activities like they have brains. This post is very knowledgeable.

  2. “Interesting read! I always assumed that all living creatures had brains of some sort. It’s amazing to discover that some animals have evolved to function without one. I wonder if these brainless organisms have unique ways of solving problems or if their behavior is purely instinctual. Great job shedding light on this lesser-known aspect of the animal kingdom!”

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