What is the Difference Between Lophotrochozoa and Ecdysozoa

The main difference between Lophotrochozoa and Ecdysozoa is that Lophotrochozoa contains mollusks and annelids, whereas Ecdysozoa contains arthropods and nematodes

Lophotrochozoa and Ecdysozoa are two animal groups of protostomes. Their mouth develops first during their embryonic development.  

Key Areas Covered

1. What is Lophotrochozoa
– Definition, Characteristics, Importance
2. What is Ecdysozoa
– Definition, Characteristics, Importance
3. Similarities Between Lophotrochozoa and Ecdysozoa
– Outline of Common Features
4. Difference Between Lophotrochozoa and Ecdysozoa
– Comparison of Key Differences

Key Terms 

Ecdysozoa, Lophotrochozoa

Difference Between Lophotrochozoa and Ecdysozoa - Comparison Summary

What is Lophotrochozoa

Lophotrochozoa is a monophyletic group of protostomic animals that includes annelids and mollusks. Also, it includes bryozoans, brachiopods, and Platyhelminthes. Annelida is an animal phylum with segmented worms. The segments are the repeating sections that collectively form the body of annelids. Each section consists of a separate set of internal organs. However, annelids lack an obvious head or antennae. Most annelids live in the soil, aiding the aeration of the soil. They feed on primary detritus and other decaying organic matter. Besides, annelids have a complete digestive system.

Compare Lophotrochozoa and Ecdysozoa

Figure 1: Anatomical Diagram of Mollusk

Furthermore, mollusks form the second-largest phylum of invertebrate animals. They live in terrestrial, freshwater, and marine habitats. The three main characteristics of mollusks include:

  • The presence of a mantle for breathing and excretion.
  • The presence of a radula for feeding.
  • The structure of the nervous system.

Other than that, mollusks have limpet-like shells on top of the body. It is made up of protein and chitin, and it is reinforced with calcium carbonate. Also, a muscular foot occurs at the underside of the body. The main body cavity of mollusks is a hemocoel through which the blood circulates. 

What is Ecdysozoa

Ecdysozoa is another group of protostomes that contains arthropods and nematodes. The main characteristic feature of Ecdysozoa is the presence of a moulting cuticle. Arthropoda is a phylum consisting of animals with jointed appendages and a chitinous exoskeleton. Arthropods can be aquatic, terrestrial, or aerial animal forms. Moreover, arthropods are triploblastic animals whose body cavity is filled with blood or haemolymph. Thus, arthropods are haemocoelomates. Importantly, arthropods represent the largest phylum of invertebrates.

Lophotrochozoa vs Ecdysozoa

Figure 2: Ecdysozoa

Moreover, Nematoda is an animal phylum consisting mostly of parasitic worms with tapered ends. Therefore, they are also called roundworms. As nematodes lack a mesoderm, their organs are always bathed in the fluid of the body cavity. Their body cavity is called a pseudocoelom. They also lack a circulatory system; the body’s cells obtain nutrients through diffusion. Nematodes have a hard outer covering called a cuticle in their epidermis. Their body surface also consists of ridges, warts, and rings. Most nematodes are dioecious animals with separate sexes. But some of them can be hermaphrodites.

Similarities Between Lophotrochozoa and Ecdysozoa

  • Lophotrochozoa and Ecdysozoa are two groups of protostomes.
  • They develop their mouth first during embryonic development.
  • They have body cavities and cuticles.

Difference Between Lophotrochozoa and Ecdysozoa


Lophotrochozoa refers to a monophyletic group of animals that includes annelids, mollusks, bryozoans, brachiopods, Platyhelminthes, and other animals that descended from the common ancestor of these organisms. In contrast, Ecdysozoa refers to a group of protostome animals, including Arthropoda Nematoda and several smaller phyla.


Lophotrochozoa contains mollusks and annelids, while Ecdysozoa contains arthropods and nematodes. 


Lophotrochozoa has a segmented body, while Ecdysozoa animals molt periodically.


In brief, Lophotrochozoa and Ecdysozoa are two animal groups belonging to the protostomes that first develop the mouth. Lophotrochozoa contains mollusks and annelids that have a segmented body. In contrast, Ecdysozoa contains arthropods and nematodes that are periodically molt. Therefore, the main difference between Lophotrochozoa and Ecdysozoa is their characteristics.  

  1. (2021, December 15). 33.2A: Superphylum Lophotrochozoa. Biology LibreTexts.
Image Courtesy:
  1. Archimollusc-en” By KDS444 – Own work (CC-BY SA 3.0) via Commons Wikimedia
  2. Ecdysozoa ” By 148LENIN – Own Work (CC-BY SA 4.0) via Commons Wikimedia

About the Author: Lakna

Lakna, a graduate in Molecular Biology and Biochemistry, is a Molecular Biologist and has a broad and keen interest in the discovery of nature related things. She has a keen interest in writing articles regarding science.

Leave a Reply