Difference between Coelomate and Acoelomate

The coelom is a cavity present between the gut and the outer body wall. It is found in animals and serves as a basis of classification for the animal kingdom.

The presence of a body cavity that is lined by mesoderm is referred to as coelom, the presence of patches of mesoderm in the body cavity is termed pseudocoelom, and the total absence of body cavity is referred to as acoelom. The animals possessing the cavity are known as coelomates or eucoelomates, and those that do not have a cavity are known as acoelomates.

The coelomic activity is usually filled with a fluid called the coelomic fluid. In the fluid, many organs such as the kidney, heart and reproductive organs are suspended.

Let us now discuss the differences between a coelomate and an acoelomate animal in the table below.

Coelomate

Acoelomate

Description

Coelomates are organisms with a fluid-filled cavity between the gut wall and the outer body wall.

An acoelomate is an organism that does not contain a fluid-filled cavity in their bodies.

Type of animal

Both vertebrates and invertebrates.

Only invertebrates.

Organs

The organs, such as the kidney and heart, are suspended in the coelomic fluid. The coelom compartmentalises the animal’s body for the free movement and growth of the organs.

The organs are not suspended and cannot move freely for growth.

Protection

The coelomic fluid acts as a shock absorber and protects the internal organs from crushing.

There is no protection of internal organs from crushing.

Classification

The coelomates are divided into Protostomes and Deuterostomes on the basis of their embryological development.

No such classification.

Nutrients

The coelom provides a space for the diffusion of gases and nutrients.

Nutrient transport occurs through passive diffusion.

Organ System

The presence of coelom promotes complex organ systems in animals.

It does not promote complex organ systems.

Examples

Annelids, molluscs, arthropods, echinoderms, hemichordates and chordates.

Platyhelminthes

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Frequently Asked Questions

What is the difference between an acoelomate, pseudocoelomate and coelomate?

Coelomates are organisms with a mesodermally lined body cavity, pseudocoelomates are organisms with patches of mesoderm on their body cavity, and acoelomates are organisms with no body cavity at all.

Does acoelomate have mesoderm?

Yes, the acoelomates do have a mesoderm, but instead of being filled with fluid, it is fully lined with tissues.

What are pseudocoelomates, and give three examples of the animals?

Pseudocoelomates are organisms that have patches of mesoderm on their body cavity. Examples: Roundworm, hookworm and pinworm.

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