Mormyrinae

Some fish look like tiny elephants.

They have a long nose. This helps them find food in the mud. These fish live in Africa.

Their brains use a lot of energy. They use more energy than any other animal. This is because they have a large brain.

The fish make tiny electric fields. They use these fields to see. They can find food and talk to each other. This helps them live in muddy water. It is a very smart way to live!

Some fish in Africa look like tiny elephants.

People call them elephantfish. They have a long part below their mouths. This looks like a trunk. They use it to find food in the mud. This group has about 170 species.

These fish have a very special way to see. They live in muddy water. They make weak electric fields using special muscles. Their skin has parts called electroreceptors. These parts feel the electric fields. This helps them find prey and talk to others.

To do this, they need a big brain. Their brain has a large part called a cerebellum. This part is so big it is called a gigantocerebellum. This large part helps them process electric signals. It helps them know if a signal came from them or something else.

These brains use a lot of power. Their brains use about 60% of their body's oxygen. This is a very high amount. Most animals use much less. Even human brains use only 20% of the body's oxygen. These fish use much more because they have a large brain and a low energy body.

Mormyrinae are a large group of freshwater fish found in Africa.

There are about 170 different species in this group. Many people call them elephantfish because of how they look. They have a long part growing below their mouths. This part looks a bit like an elephant's trunk or a tusk. They use this part to find small animals buried in the mud. Some people also call them tapirfish.

These fish have a very special way to sense the world. They live in water that is often very muddy. To see through the mud, they use something called electroperception. They use special muscles to make weak electric fields. Their skin has three types of electroreceptors to feel these fields. These sensors help them find food and talk to other fish. They even use special organs called Knollenorgans to help with this.

Using electricity to sense things is a hard job for a brain. The fish must know if an electric signal is their own. They must also tell if the signal comes from a neighbor or the environment. To do this, the brain makes a copy of every electric pulse it sends out. It then compares that copy to the signals it feels. This helps the fish understand its surroundings. This complex work happens in a special part of the brain.

Because of this hard work, these fish have a very large cerebellum. The cerebellum is a part of the brain used for processing. In these fish, it is so big it is called a gigantocerebellum. This large brain part uses a huge amount of energy. In 1996, a researcher named Göran Nilsson studied this at Uppsala University. He found that these brains use about 60% of the fish's oxygen. This was a big discovery because people once thought human brains held the record.

Most animals use much less energy for their brains. Usually, a brain only uses between 2% and 8% of a body's energy. Human brains use about 20% of our body's oxygen. The mormyrinae fish are different because they are ectothermic. This means their bodies do not use much energy to stay warm. They have a large brain inside a low-energy body. This combination makes their brain energy use very high compared to others.

Mormyrinae is a large subfamily of freshwater fish found in Africa.

These fish belong to the order Osteoglossiformes and the family Mormyridae. They are the largest subfamily within that order, containing about 170 different species. Many people call them elephantfish because of a long protrusion located below their mouths. This feature looks like a tusk or a trunk, which helps them detect invertebrates buried in the mud. Some people also refer to them as tapirfish.

These fish are famous for a remarkable biological trait involving their brains. They possess a very high brain-to-body mass ratio. This is due to an enlarged part of the brain called the cerebellum. Because this cerebellum is so large, scientists call it a gigantocerebellum. This specialized brain structure is essential for a process called electroperception. This allows the fish to sense their environment through electrical signals.

Electroperception works through a complex series of biological steps. First, the fish generate weak electrical fields using specialized electric organ muscles. Their skin contains three different types of electroreceptors to detect these fields. These sensors help the fish with hunting, electrolocation, and communication. For communication specifically, they use specialized electrical detection organs called Knollenorgans. This system is vital because these fish often live in very muddy waters.

Processing these electrical signals requires very advanced neurocircuitry. The fish must be able to distinguish between their own electric fields and those created by others. They must also tell how their environment distorts their own signals. To manage this, the brain creates an efference copy of every electrical discharge it sends out. The fish then compares this copy to the actual electric field it detects. The gigantocerebellum plays a key role in processing this comparison. This complex task is what makes their brain activity so intense.

In 1996, a researcher named Göran Nilsson at Uppsala University made a major discovery. He found that mormyrinae brains consume about 60% of the fish's total oxygen. This is a staggering amount of energy for a single organ. Before this, scientists believed the human brain held the record for energy consumption. However, the human brain only uses about 20% of the body's oxygen. Most animals have brains that use only between 2% and 8% of their body's energy. Even primates only use about 11% to 13%.

There are specific reasons why the mormyrinae hold this zoological record. Their brains make up 3.1% of their body mass, while a human brain is 2% of body mass. Furthermore, these fish are ectothermic, meaning they do not use much energy to maintain body heat. The energy used by the bodies of ectothermic animals is about 1/13 of that used by endotherms. Because their bodies require so little energy, the large brain's demand for oxygen represents a much higher percentage of the total. In contrast, animals like bats or crows have high energy needs because they are endothermic.

It is interesting to note that the energy consumption per unit of brain mass is not actually the highest. The brain mass of a mormyrinae fish uses 2.02 mg g⁻¹ h⁻¹ of oxygen. This is actually lower than the rate in Salmonidae fish, which is 2.20 mg g⁻¹ h⁻¹. It is also lower than the rate in humans, which is 2.61 mg g⁻¹ h⁻¹, and rats, which use 6.02 mg g⁻¹ h⁻¹. Their record is unique because of the ratio between the large brain and the low-energy body. They are a perfect example of how specialized survival needs can drive extreme biological evolution.

The classification of these fish has also been studied closely. Scientists originally used osteology, or the study of bones, to divide Mormyridae into two subfamilies. These are Mormyrinae and Petrocephalinae. Modern researchers have since confirmed this classification using molecular phylogeny methods. These methods look at genetic relationships to see how species are connected. This ensures that our understanding of the mormyrinae is based on both physical traits and DNA.