When you go for a swim, you can sense the functionality of your backbone. It may drive you to wonder, do fishes around us use their backbone like we do to swim? Do they even have a backbone?
Fishes are Vertebrates, which is a very academic way to say. They indeed have backbones. Except for the Hagfish, all the species have vertebral columns. Some fish’s backbones are made of cartilage, while others have bone structures.
Fishes can be tiny and cutesy creatures, but their body will make you wonder at every step. So, sit tight and dive into the world of backbones of the fish kingdom.
What Is A Vertebrate?
A vertebrate basically means animals and creatures do have vertebrae, aka backbones. Since fish is vertebrate, their body possesses a spinal cord or backbone.
Fish is a significant member of the phylum Chordata, which translates as animals with backbones. They fall with other vertebrate species such as mammals, amphibians, reptiles, and birds. The only difference is fishes are aquatic creatures living under the water.
The journey of backbone dates back to 525 million years ago when the Cambrian explosion diversified organisms around the world and multiplied significantly. Their body grew larger, but without any steady structure, they became wobbly and unbridled to control.
There are 65,000 species with vertebrae which make up 3% of organisms of the whole world. Since vertebrae grew inside the body of fish, they became a part of the phylum Chordata.
The vertebral column is the connecting point of many parts of the fish. It connects the jaws, intramuscular bones, skulls, and ribs. The total structure creates the skeletal system of the fish. Depending on the type and species, some fishes may or may not have jaws, ribs, or other parts of the system. But each and every vertebrate fish possess a backbone that acts as a connector or jointer.
Do All Fishes Have Backbones?
Setting aside a few exceptions, we can find all the fishes with vertebrae. Evolution has presented us with three types of fish based on the vertebral column. Jawless, Cartilaginous, and bony fish are basically types of vertebrates that have some differences in traits, but all of them have vertebrae.
Instead of having a vertebral column, jawless fish have vertebral arches. That backbone doesn’t look straight or curvy on the bottom layer. It is shaped like an arc, and the spinal cord is made of cartilage instead of bone structure. Lampreys are a classic example of jawless nature. Jaws, stomachs, and fins are missing from the Lampreys, and they look more like a snake than fish.
As the name suggests, cartilaginous fish possess a backbone made out of cartilage. Their endoskeleton has primarily buildup on cartilage and is analogous to jawfish. However, unlike jawfish, cartilaginous have jaws and fins made out of scales. Their backbones are composed of two tubes, namely, the upper and lower. Their backbone structure and material are different from bony fish.
95% of the fish today are from this type of fish which we usually see in seas, oceans, rivers, and at our aquariums. Their endoskeleton is made of bones; hence the name bony fish came. Their exoskeleton is made of thin boney plates that are attached to the vertebrae. Globefish, catfish, clownfish, sea horses, and goldfish are from this category.
What Fishes Don’t Have Backbones?
Fishes are generally vertebrates, but some exception always lingers in our bio-diverse world. Hagfish and snot eels are such exceptions which are fish but invertebrates in nature possessing no backbones. In fact, both of them are from the jawless fish category. Their outlook and traits are similar to jawless fishes.
Their structure is large in size and slimy in texture. They prefer to eat dead fish, and their swim pattern looks more like crawling than swimming due to the absence of a backbone. They don’t have any jaws or fins, so they use their tongue to devour their food. Their tail has some sort of arches, but those can’t be categorized as a backbone. Except for the backbone part, hagfish are similar to Lampreys in nature.
No matter what the name suggests, jellyfish and starfish are not really fish. They belong to the Cnidaria phylum and are basic invertebrates. They do not even possess the lungs, hearts, and fins like fish, and their way of living is very analogous to the fish genre.
Why Do Fishes Need Backbones?
In human life, we do not even question the value of a backbone since it helps us to walk and stand and to move our muscles freely. But if aquatic life, having a backbone seems like a redundancy since fish do not have to stand or walk. They swim horizontally, and in the absence of a vertebral column, they could swim in curvier ways. But fishes need backbone since it comes with lots of benefits. Let’s see what those are.
Attaches The Muscles
Fish muscles are spread out to their body with some bones in here and there. Without a spine, their muscle will be a blob of meat without any support. The muscle attaches to the spine and backbone, helping them to move the way they want. Without a backbone, fish could not move so freely and actively.
Supports The Body
Fishes backbone spreads from the skull to the trunk supporting from the top of the head to the start of the tail. Backbones also have two layers- bottom and upper. The ribcage spreads out from the top layer to the bottom, protecting the body and attaching organs for support and movement. Fins also get support from the spine, and the spine helps to move the muscle, which directs the fin movement eventually.
Protect The Nervous System
Like any other species, fishes have nervous systems that spread like a web all around the body. Fishes are extra sensitive to touch or sudden movement due to poor support of nerve roots. However, they are quite comfortably secured to the backbones so that stress and instead attack can’t shake their nervous points too easily, and they are bonded tightly.
Gives The Whole Body A Structure
Fish do not have a very stable structure in their body. They do not have hands and legs like ours, and they are just one piece of meat without any curve or section. What gives them meaning is their backbones which help them to stay steady and move as they want. The backbone determines the ultimate shape of the body of any fish.
Move The Body
Backbones help the fish swim systematically in two ways. Firstly, it supports the fins and tails, which lead the body to move forward as they swim. The body parts which are related to the movement or swimming of the fish are somehow connected with the backbone. Secondly, the backbone keeps the parts in coordination so that they don’t swim erratically.
Avoids Accidents And Injuries
Like Cordata, fish also take after their backbone and shapes up the way their backbones look. It leads their way, controls their muscles, and helps to move fins and bones. Without the vertebrae, fish could hardly control their body and with being susceptible to injuries and accidents. They would float like a blob and hit every corner without vertebrae.
Produces Blood Cells
We all know that hemoglobin is born from bones and backbones that help to create red blood cells in the body, which are a vital part of our blood. Fish also follow the same mechanism to create red blood cells and hemoglobin in their body. Without backbones, fish could not have balanced red blood cells and platelets in their system.
The Process Of Backbone Growth
The backbone growth started its journey 525 million years ago with the rapid evolution called Cambrian Period. As fish come from eggs, they certainly do not grow with the backbone of their body. So, what drives them to grow backbones when they are fries? The vertebrates which dwell on land develop their spine with the help of a group of cells called somites.
Aquatic fishes, on the other hand, use two types of cells group. The first one is somites, and the second one is called chondroblasts. In ancient times, the original ancestors of jawed fish used only somites cells to develop the spine. However, from the evolution of ray-finned fish, separate cells were employed for the backbone development of vertebrate fishes.
Do Fish Have Bones?
The answer to that question will change depending on the type of fish you are referring to. Remember, we discussed the types of fish above in this article. Well, the same statement is applicable to the bone condition of fish as well. Jawless fishes do not have bones, but their spikes are made of cartilage.
Cartilaginous fish that belongs to the Chondrichthyes family also don’t possess bones. However, their backbones and spikes are made of cartilage. Their exoskeleton and endoskeleton don’t have a hint of bone but only cartilage. But their cartilage is different from cartilage found in the human body as they are sturdy, strong, hard, and full of minerals.
As the name suggests, bony fish are fishes that possess actual bones. They belong to the Osteichthyes family, consisting of 93% of the vertebrate fishes found in saltwater and freshwater. Their skeleton and skull are made out of bones, not cartilage. Bony fish have a proper skeleton system with vertebral columns, cranium, jaw, ribs, and intramuscular bones.
Even though fishes are different parts of animal kingdoms, and we hardly associate them with humans, they have traits and structures whose similarities can astonish us. Fish having backbones is another wonder of our organic world, and their functionality and durability help to capture the strength of the wilderness.