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Difference Between Protostomes and Deuterostomes

Last updated date: 27th Feb 2024
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Introduction: Explaining Protostomes and Deuterostomes

Protostomes and deuterostomes represent two major evolutionary branches in the animal kingdom, showcasing contrasting developmental processes and resulting in distinct body plans. protostomes, which includes arthropods, mollusks, and annelids among others, follows a developmental pathway where the first opening in the embryo, called the blastopore, develops into the mouth. On the other hand, deuterostomes, which includes chordates and echinoderms, takes a different approach: the blastopore becomes the anus, and the mouth forms later. These contrasting developmental patterns have profound implications for the subsequent development of the animals, including differences in the formation of body cavities (coelom), the fate of embryonic cells, and the overall organization of body structures. Understanding the distinction between protostomes and deuterostomes and  helps us to Explain protostomes and deuterostomes and  appreciate the incredible diversity and complexity of the animal kingdom.

What is Protostomes and Deuterostomes?


Protostomes refers to a group of animals in which the first opening formed during gastrulation, called the blastopore, develops into the mouth. It includes the largest and most diverse phylum in the animal kingdom, Arthropoda, which consists of insects, crustaceans, arachnids, and more. Arthropods make up about 80% of all known animal species.


Refers to a different evolutionary lineage where the blastopore develops into the anus, and the mouth forms from a secondary opening. Deuterostomes have given rise to diverse and iconic animals, including fish, amphibians, reptiles, birds, and mammals, including humans.

Characteristics of Protostomes and Deuterostomes


Developmental Pattern:   In Protostomes, the blastopore develops into the mouth, and the anus forms later.

Cleavage Pattern:  Protostomes typically exhibit spiral and determinate cleavage, where the fate of cells is determined early in development


Developmental Pattern: In Deuterostomes, the blastopore develops into the anus, and the mouth forms later.

Cleavage Pattern: Deuterostomes generally display radial and indeterminate cleavage, where cell fate is determined at a later stage.

Difference between Protostomes and Deuterostomes







Forms by schizocoely

Forms by enterocoely


Fate of cells

Determined early in embryonic development

Determined later in embryonic development



Limited ability to regenerate

Extensive ability to regenerate


Nervous System

Protostomes are composed of a solid, ventral nerve cord.

Deuterostorms are composed of a hollow nerve cord and pharyngeal gill slits.


Development of Coelom

Protostomes are called schizocoelomates, since the coelom is developed by splitting of the solid mass of the embryonic mesoderm.

Deuterostomes are called enterocoelous since the longitudinal pouches of the archenteron forms the coelom.


Protostomes and deuterostomes are two major evolutionary branches in the animal kingdom with distinct differences in embryonic development. protostomes develops with the blastopore forming the mouth, while deuterostomes develops with the blastopore forming the anus. protostomes exhibits spiral and determinate cleavage, with cell fate determined early on, while deuterostomes exhibits radial and indeterminate cleavage, with cell fate determined later. Coelom formation differs, with protostomes forming it through schizocoely and deuterostomes through enterocoely. These developmental disparities give rise to diverse characteristics, body plans, and evolutionary pathways within each lineage.

FAQs on Difference Between Protostomes and Deuterostomes

1. How does the nervous system differ between protostomes and deuterostomes?

In protostomes, the nervous system usually develops as a solid ventral nerve cord, while in deuterostomes, it typically develops as a dorsal hollow nerve cord.The difference in the position and structure of the nerve cords reflects the distinct developmental patterns between protostomes and deuterostomes. These differences have implications for the organization and function of the nervous system in each lineage, contributing to the diverse neurological capabilities and behaviors observed in animals belonging to these groups.

2. Can you provide examples of animals belonging to protostomes and deuterostomes?

Protostomes includes diverse groups such as arthropods (e.g., insects, crustaceans), mollusks (e.g., snails, clams), and annelids (e.g., earthworms). deuterostomes includes chordates (e.g., vertebrates, including humans) and echinoderms (e.g., starfish, sea urchins).These examples represent a small selection of the diverse range of animals found within protostomes and deuterostomes. Each group exhibits unique characteristics and adaptations that have allowed them to thrive in various environments and play important roles in ecosystems.

3. What are some implications of the differences between protostomes and deuterostomes?

These differences in development and characteristics have profound impacts on the overall body plans, complexity, and evolutionary pathways of animals within each lineage. They contribute to the incredible diversity observed in the animal kingdom.Understanding the differences between protostomes and deuterostomes provides insights into the incredible diversity, adaptations, and evolutionary processes within the animal kingdom, enhancing our knowledge of the natural world and its intricate interconnectedness.