Do Fish Have a Backbone? You Will Be Surprised

Fish are the most common aquatic creatures, making up a significant part of the marine world. They are gill-bearing creatures that do not have limbs with digits. They possess fins and scales that make them survive and thrive in their world. But do fish have a backbone?

All fish are vertebrates, which means that they all possess backbones. The only exception to this is the hagfish, which does not have a backbone. All fish have two constant features; they have a backbone, and they live in water.

fish backbone

Do All Fish Have Backbones?

Not all fish have backbones, but most of them have. Most fish have two traits; they can live in water, and they have a backbone. They can live in water because they have several characteristics that aid this characteristic.

They possess gills that help them harness oxygen in water, ensuring they respire and get oxygen to the required body organs.

They also have fins that help them swim through water; it is the way they move since they do not have limbs like other animals.

Another trait that classifies fish is their backbone. Every fish has a spine that helps it move through water, except one; the hagfish.

The hagfish are the only classified fish type that do not have a backbone but possess a skull.

Hagfish belong to the class Myxini and the order Myxiniformes, having the shape of an eel. Most people refer to it as the slime eel. Hagfish do not have backbones, but they do possess rudimentary vertebrae.

What’s the Purpose of a Backbone in a Fish?

The backbone is an essential part of the body, both on land, arboreal, and aquatic animals. The spine has several functions that make it a vital organ in fish. Here are some functions of the backbone;

  • Support : One of the skeleton’s functions in the body is to provide support to soft and vital organs. The backbone is also a part of the skeleton, making support one of its functions. The fins are an extension of the spine, causing the backbone a sort of support for them.

The backbone also supports the head to the trunk of the fish. The fish’s spine runs from the head to the fish’s tail, making the backbone the most significant fish skeleton structure after the skull.

The backbone also supports the ribs of the fish. Fish have two ribs attached to the upper and lower part of their spine. It also provides support to other parts of the fish’s skeleton.

  • Protection : Protection of vital organs is one of the functions of the backbone in fish. The spinal cord is an essential organ in the body, but it is very fragile. It runs through the spine while the backbone protects it.

The spinal cord is a collection or pack of nerves that send information from the brain to other parts of the body. It is, in other words, the message pathway between parts of the body and the brain. This organ is essential, and the backbone plays a vital role in protecting and keeping it safe.

  • Movement : The backbone also helps in the movement of the fish. Most of the fish’s parts that aid its water movement are directly or indirectly connected to the spine. When the fish wants to move, it moves its backbone, which will later cause the fins and other parts to move.

The backbone is useful to fish, especially when steering or maneuvering. Fishes maneuver as a result of their spine that can turn and make flexible bending.

  • Structure : The main parts of a fish skeleton is the head and backbone. Other skeleton parts are not very significant as they are directly or indirectly attached to the spine. The shape and structure of a fish depend on its backbone; the fish takes after the backbone’s shape.

Without the backbone, the fish will be like a stack of meat without anything to hold it up. The spine plays a vital role in the structure, movement, support, and protection of critical organs in the fish. If a fish loses its backbone, there is a high chance it will lose its life.

How do Backbones Grow in Fish?

The growth of backbones results from the evolution and diversification of events that happened and altered the development, structure, and shape of fish. Fossils showed that every vertebrate fish does not have backbones; they all evolved into having it due to environmental adaptation.

Some suggest that the action of crashing waves on the fish caused it to develop into a structure that can withstand the crash.

Whatever the theory behind the growth of backbones in fish, we should all know that fish grow backbone using two different types of cells; chondroblasts and somites.

It includes a process that starts from the amniote embryos till the vertebrae become fully developed.

In amniote embryos, the somite derived cells of sclerotome that migrate and differentiate, giving rise to chondrocytes and then osteoblasts.

This process replaces the cartilage vertebrae with bone. It is a process known as endochondral ossification.

What Type of Fish Has no Backbone?

All fish are vertebrates; they all have backbone except the hagfish. The hagfish is the only one classified without a backbone, although it has rudimentary vertebrae. It possesses a skull that protects the brain, but not a backbone.

The hagfish has a shape like that of an eel, making people refer to it as the slime eel. They have dull pink colors, a skin that covers their body. There has been a controversy on the fish’s classification, but it is a fish classification as of the latest report.

What Fish Has the Most Bones?

There are two main types of fish based on their bone structure; the bony and cartilaginous fish. Bony fish have more bones than cartilaginous fish, which is where they derived their name. The Shad is a bony fish with the most bones.

The fish with the most bones are pickerel, carp, northern pike, squawfish, herring, carp, buffalo fish, mooneye, etc., but their bones are not as much as the Shad. TheShadd has about 3000 bones in its body, and that makes it quite challenging eating. Aside from having many bones, the Shad is also a tasty fish.

Therefore, it earned its Latin name Sapidissima, which means tastiest.

What is Fish Bone Called?

The fishbone refers to any bone present or found in a fish. Most people have different names for it; some can be casual while others might be official. Some people refer to it as cartilage, while some call it ossein.

Other names for fishbone include; osseous matter, bone tissue, osseous tissue, skeleton, etc.

Are Fish Invertebrates?

Fish are vertebrates with only a few exceptions. A fish being vertebrate means it has a backbone, which is a common feature. The only exception is the hagfish; it does not have a backbone but has a fish classification.


Fish must have backbones as it plays an essential role in the routine activities of the fish. It protects vital organs, supports other parts of the skeleton and body, aids movements as the parts that help the fish are directly or indirectly attached to it and provides shape and structure to the fish. These functions do not apply to the hagfish, the only fish without a backbone.