The brain has become the object of study of various investigations, since the human being still cannot fully decipher the functioning of each sector. However, Did you know that there are animals without brains? Contrary to what you may think, this does not mean that they are incapable of developing normally, because they actually have with other mechanisms to fulfill its life cycle according to the demands of its environment.
If you are interested in knowing the names and characteristics of these very particular species, then you cannot miss the following article on our site. Keep reading!
How do animals without brains survive?
Although it would be unfeasible for humans, there are many species of animals on the planet that lack a brain and that, despite this, carry out their life cyclenormally. Most of these species are marine animals, as many retain morphologies similar to those they had thousands of years ago, before life began to exist on land.
How do these animals survive? Each species has particular adaptations that allow it to exist, feed, reproduce and excrete, although it is difficult to speak of a single physical structure that would "replace" the brain. In fact, whether it is a spinal system, peculiarly developed arms or tentacles, ganglia, nerve networks, or another structure, each species has different adaptations that allow it to survive.
These are some of the brainless animals that exist:
1. Sea stars
The starfish belong to the order Asteroidea and are invertebrate animals that inhabit the deep sea. They are characterized by having between 5 and 50 arms, depending on the species, which they use to reproduce, hunt and excrete. The life cycle of starfish is therefore complete.
These marine animals do not have a proper brain, but they do have a nervous system made up of nerves and anervous plexus that send information from different parts of the body, functioning as a kind of brain "distributed in parts". Thanks to this, they are able to receive and recognize different stimuli, and send "orders" about what each part of the body should do.
two. Sea cucumber
The Sea cucumbers are echinoderms characterized by having a long and soft body, and by living in the depths of the oceans. Like starfish, cucumbers are among the animals without brains and hearts
How do they survive? First of all, they have different nerve endings in their small tentacles and pharynx, so they receive stimuli and send responses according to what they perceive from their environment. With respect to the absence of a heart, they have a aquifer vascular system, which transports water, proteins and potassium ions throughout the body. Thanks to this, the sea cucumber is able to perform all its vital functions.
3. Jellyfish
Jellyfish belong to the Medusozoa subphylum and are among the oldest marine species in the world, since they appeared during the Cambrian, five hundred million years ago. They are among the animals without a nervous system, in addition to not having a brain, and some species stand out for being part of the list of animals that glow in the dark.
They survive thanks to the fact that their skin is covered with a network of interconnected nerves that send information about what they touch. this system is called diffuse or reticular system In addition, some species have ocelli, organs capable of detecting light.
4. Coral
Under the name of coral are enclosed different types of marine organisms that are organized by forming colonies of small individuals. Although at first glance they look like rock formations or plants, especially when they form large reefs, they are actually animals.
Corals don't have a heart, nervous system or brain, but are made up of millions of tiny individuals called polyps, which are organized to create large coral formations and catch prey, as well as perceive everything around them, with small tentacles that have nerve endings.
5. Anemones
The Anemones belong to the order Actiniaria and, like corals, at first glance appear to be plants, but in reality they are marine animals that grow attached to a sand or rock substrate.
They do not have a brain or a heart, but it is possible to state that they have a primitive nervous system that allows them to maintain their vital balance according with the stimuli they receive from the environment. They also do not have formed organs, but they do have tentacles and "organelles", simple structures with stinging properties.
6. Sea sponges
The sponges, animals of the phylum Porifera are among the brainless marine animalsand are among the oldest in the world, as they have inhabited the oceans since the Precambrian Their bodies have pores and internal channels with which they can pump water, in addition to having totipotential cells, which are capable of changing function according to what the sponges need.
Thanks to this last characteristic, sponges do not require specific organs or a defined nervous system, since all their vital activity is carried out at the cellular level.
7. Portuguese man-of-war
The Physalia physalis or Portuguese man-of-war is an organism formed by a colony of individuals, but whose appearance is similar to a jellyfish. They measure between 15 and 30 centimeters and are made up of hydrozoans , very small organisms that group together to survive. In this colony relationship, the different organisms distribute essential vital functions, although they lack a defined nervous system, heart or brain.
8. Sea Lily
The sea lily is a type of echinoderm, like the stars, of the class Crinoidea. It is characterized by a "plant"-like appearance with numerous ramifications. They are very old, since there are records of them from the Paleozoic. They do not have a brain, but like other echinoderms, they have a nerve network that allows them to perceive what is happening around them.
9. Ascidians
The ascidians are other curious marine animals that, at first glance, are difficult to differentiate from simple plants. They live adhered to rocks and seashells, from where they capture food particles thanks to the water currents they absorb. Little is known about this species, but they lack a nervous system, brain, and heart.
10. Lancetfish
The lancet fish (Branchiostoma lanceolatum) is one of the marine animals without a brain, since it is avery primitive species It measures only 5 centimeters and, apart from lacking a brain, it also does not have a skeleton or sensory organs. The lancet has a poorly defined nervous system , which is also not protected by vertebrae.
eleven. Ctenophores
The ctenophores are a phylum of little-known marine animals. There are around 200 species and in many cases they form a large number of that group of organisms that we call "plankton".
Their bodies are simple and variable, as some have tentacles and a jellyfish-like shape, while others do not. They lack a circulatory or excretory system, but have a simple nervous system, though no brain Like other marine animals, the nervous system is distributed in networks through of the body and, thanks to this, they are able to receive stimuli.
12. Leeches
Leeches (Hirudinea) can survive in Marine, terrestrial or freshwater environmentsThey are characterized by having an elongated body, somewhat fat and viscous. They are predatory animals and some species feed on blood. Leeches Do not have a brain, but they do have nerve networks that are distributed throughout the body thanks to small ganglia and sensory organs.
13. Earthworm
The earthworms (family Lumbricidae) are among the brainless land animalsDespite their name, they prefer to live in humid environments, although they are popular for digging holes in the ground to move around. The anatomy of this species is simple: a mouth, an anus and a series of muscles throughout the body.
They have a circulatory system dominated by a central valve that acts as a heart. With regard to the nervous system, they do not have a formed brain, but they do have several ganglia that fulfill the function of receiving the nerve impulses that are perceived.
Do insects have brains?
As you may have noticed, most animals without brains are marine, but what about land animals? They usually have a fully formed brain, even in small species such as insects. Insects have a well-defined nervous system,which is distributed in the head, thorax and abdomen, where nerve ganglia are located in different quantities; these ganglia capture nerve impulses or stimuli.
Insects have a "main" brain and some "secondary" ones, called ganglionic masses The main brain is located above the esophagus, which is why it is called supraesophageal ganglion The other three secondary brains are:
- Protocerebro: it is located in the esophagus, where originally that of the annelids was found. Takes care of vision.
- Deutocerebro: it is located in the esophagus and connects with the antennae, appendages that perceive olfactory stimuli.
- Tritocerebro: smaller in size, it is located below the main brain and controls the sympathetic nervous system, that is, visceral functions, and taste.
Do fish have brains?
The belief has spread that fish have little intelligence and short memory, therefore, it is common to think that they do not have a brain. However, Most of these vertebrates have a brain (except for very primitive species) as well defined as the rest of their vital organs.
Although it is usually considerably small in size compared to the rest of the body, this vital organ is divided into several regions, just like than that of terrestrial species. In addition, the brain of fish has a unique feature: even outside its body, it is capable of continuing its neural activity for several hours.
