Protostome facts for kids

Quick facts for kids Protostomia Temporal range: Ediacaran – Recent
The caribbean reef squid, an example of a protostome
Scientific classification
Kingdom:	Animalia
(unranked):	Nephrozoa
Superphylum:	Protostomia Grobben, 1908
Groups
Ecdysozoa Lophotrochozoa Platyzoa

Protostomes are a very large group of animals. They are part of a bigger group called Nephrozoa. Scientists use this term to group many different kinds of animals together. It helps them understand how animals are related.

Protostomes are different from another big group called deuterostomes. Both groups are part of the Bilateria, which means they have bodies with two similar halves. The main difference between protostomes and deuterostomes happens when they are still tiny embryos.

What Makes Protostomes Special?

The biggest difference between protostomes and deuterostomes is how their first opening forms. When an animal embryo starts to grow, a small opening appears. This opening is called the blastopore.

How the Mouth Forms

In protostomes, this first opening becomes the animal's mouth. This is where the name "protostome" comes from. "Proto" means first, and "stoma" means mouth. So, it means "first mouth."

How Deuterostomes Are Different

In deuterostomes, the first opening becomes the anus. The mouth forms later as a second opening. This is why they are called "deuterostomes," meaning "second mouth." This small difference in early development is a key way scientists group animals.

Main Groups of Protostomes

Scientists study the DNA of animals to learn how they are related. Based on DNA, protostome animals are divided into three main groups. These groups include many animals you might know.

Ecdysozoa

This group includes animals that shed their outer layer as they grow. This process is called molting or ecdysis.

• Arthropods: This includes insects, spiders, and crabs. They have hard outer shells.
• Nematodes: These are also known as roundworms. They live in many different places.

Platyzoa

This group includes animals that are often flat or very small.

• Platyhelminthes: These are flatworms, like tapeworms. They have simple bodies.
• Rotifers: These are tiny animals often found in fresh water. They have a wheel-like structure near their mouth.

Lophotrochozoa

This group includes animals that often have a special feeding structure or a unique larval stage.

• Molluscs: This group includes snails, clams, and octopuses. Many have soft bodies and shells.
• Annelids: These are segmented worms, like earthworms and leeches. Their bodies are divided into many rings.

These groups show how diverse protostomes are. They include animals living in almost every environment on Earth.