6 animals that possess the "weirdest" hearts on Earth

Articles Aug 08, 2019 02:55

The natural world is home to countless animals. And most of them still hold a lot of mysteries to us.

Squids have 3 hearts, cockroaches have the same heart rate as human, zebrafishes can regenerate their hearts... There are so many interesting things you might not know about the animal world. Today, let's talk about heart, animals' hearts. And be prepared, because the facts below will surely shock you.

Soft-bodied animals have up to three hearts

Aquatic species such as octopus, squid and starfish actually have three hearts. To be precise, they have two branchial hearts which help them absorb oxygen and a main heart which pumps blood around the body.

6 animals that possess the weirdest hearts on Earth

Fun fact: Soft-bodies animals' blood isn't red. In fact, it is blue because the cells contain many copper. For humans and mammals, our blood is red because our cells have hemoglobin which contains a lot of iron.


Like other insects, cockroaches have a special circulatory system, where their blood does not always fill all vessels, but only revolves around 12 to 13 main ones. Their dorsal vessels help transfer oxygen-absorbed blood to their heart. However, their heart does not serve as a tool to pump blood throughout the body like in other animals.

6 animals that possess the weirdest hearts on Earth

This is because cockroaches and other insects breath through spiracles on the body instead of lungs, so their blood does not need to carry oxygen from one place to another.


Earthworms don't have any heart but they have up to five body parts called "fake hearts". These fake hearts are not supposed to pump blood, but only to carry out the contraction of blood vessels to help blood circulation take place. In addition, earthworms don't have lungs and they absorb oxygen through their moist skin.

Maybe you're interested in: ​​​​​​​Can animals hold their breath for a long time?

6 animals that possess the weirdest hearts on Earth

Earthworms have red blood because their blood contains hemoglobin, a protein that carries oxygen. However, unlike humans, they have an open circulatory system, so hemoglobin only driftes between the remaining substances rather than being absorbed or metabolized.


If a zebrafish's heart is damaged, it will immediately recreate a new one. Researchers have discovered that zebrafishes can regenerate 20% of damaged heart muscle in just two months.

Just like human liver can regenerate itself, and reptiles or amphibians can regrow their own tail, the zebrafishes's ability to regenerate their heart is at the forefront of the study of cardiovascular development. However, the heart of this species is extremely special because they have only one atrium and one ventricle and has two completely different structures from the human heart. 


A whale's heart has four chambers and is known to be the largest in the animal world. It must be an extremely large and extremely healthy heart to pump oxygen pump throughout their gigantic body. A blue whale's heart weighs 589kg, equivalent to the weight of nearly 9 adults.

Maybe you're interested in:Effects of antibiotic use in animals on human health

6 animals that possess the weirdest hearts on Earth

A frog

Most mammals and birds' hearts have four chambers, while frogs have only three, including two atria and one ventricle. This type of heart is responsible for filtering the oxygen the body absorbs, moving it through the lungs and pumping it to the entire body. For human heart, the oxygenation of blood cells and the separation of oxygen from these cells are two completely different processes, but for frogs, there is a muscle called cardiac muscle which keeps these two processes working independently in the same ventricle.

6 animals that possess the weirdest hearts on Earth

Frogs not only absorb oxygen through their lungs but also through their skin. A frog's heart also works by its own principle - blood cells enter the right atrium, come out of the ventricle, and move to the lungs and skin to get oxygen. Then blood cells that have absorbed oxygen return to the left atrium, to the ventricle and bring oxygen to the entire body.

Watch next: The Strangest Creatures from the Sea!

Related Topics