Protostomes and Deuterostomes
The animal kingdom is diverse in terms of morphology, anatomy, and physiology. Despite the differences, one thing that remains common among most animals is that they all start life as a single cell. As the organism attains maturity, it develops some unique characteristics that set it apart from others and help in the systematic classification of animals into different groups. One such group of animals are called the metazoans whose body cells are differentiated into tissues and organs. Based on the embryonic development of these metazoans, they are classified into two groups - protostomia and deuterostomia (or protostomes and deuterostomes).
Protostomes
The word protostome is derived from the Greek words “proto” meaning first, and “stoma”, which means opening or mouth. In literal terms, protostome means ‘first mouth’. The reason for this naming is based on their mode of embryonic development. When the embryo develops, the protostomes first form the mouth from the blastopore, and the anus develops later after the mouth has been created.
A protostome is a group of animals that includes invertebrates like arthropods (insects and crabs), molluscs (clams and snails), and worms of phylum Annelida. Developments in the last few decades in molecular biology techniques such as DNA sequence analysis has suggested that protostomes can be divided into two major super phyla or groups called Spiralia and Ecdysozoa. While Spiralia includes Platyhelminthes, molluscs, and annelids, Ecdysozoa comprises nematodes and arthropods.
Deuterostomes
The word deuterostorme also has a Greek origin; “deutero” means second, and “stoma” means mouth or opening. Thus, deuterostome translates to ‘second mouth’. In deuterostomes, the opening at the bottom of the gastrula, known as the blastopore, forms the anus. The mouth is formed at later stages of a deuterostome’s embryonic development. In deuterostomes, the anus and the mouth are located at the opposite ends of the blastopore, and a digestive tract develops in the middle to connect the mouth and the anus.
Deuterostomes further have three significant classifications which are - Chordata, Echinochordata, and Hemichordata. Chordata includes all the vertebrates like birds and mammals. So, are humans deuterostomes? Well, yes, they are!
Echinochordata and Hemichordata comprise invertebrates. While Echinochordata includes starfish, sea urchins, and sea cucumbers, Hemichordata contains grapholites and acorn worms.
(The image will be Uploaded Soon)
Difference Between Protostomes and Deuterostomes
The most significant difference between protostomes and deuterostomes arises due to the dissimilarities in their embryonic development. In protostomes, the blastopore forms in the mouth, but in deuterostomes, the blastopore is involved in the development of the anus.
Now let us go through some other striking differences between protostomes and deuterostomes:
Origin of Mouth and Anus: In protostomes, the origin of the anus is secondary, but in deuterostomes, the formation of the mouth is secondary.
Origin of Mesoderm: The archenteron is the rudimentary alimentary canal formed during the early stages of embryonic development that later forms the mesoderm and endoderm. The development of archenteron is not seen in protostomes, but, for deuterostomes, the primitive gut formation takes place in early embryos.
Late Gut Development: In protostomes, the anus is formed by tunnelling of the gut into the embryo. But in deuterostomes, the formation of the mouth is by the gut tunnelling into the embryo.
Development of Coelom: In protostomes, the body cavity of the coelom is formed by splitting the mesodermal layer. Thus, they are schizocoelomates since the coelom is created by schizocoely. On the other hand, the deuterostomes are enterocoelomates where the body cavity or the coelom is formed by the mesoderm pinching off from the gut.
Type of Cleavage: In protostomes, the kind of cleavage is determinate, meaning that the blastomere of the early embryonic stage is incapable of developing into independent embryos. But deuterostomes undergo indeterminate division whereby the early blastomeres can develop into complete embryos.
Nervous System: Protostomes have a solid, ventral nerve cord. In deuterostomes, the nerve cord is hollow, with some possessing pharyngeal gill slits.
Body Complexity: Deuterostomes have a more evolved and complex body organisation than protostomes.
Type of Cell Ciliation: The cells in protostomes are multi-ciliated, but those in deuterostomes are mono-ciliated.
Number of Phyla: Protostomes include more species and phyla compared to deuterostomes.
Classification: Protostomes can be grouped into Spiralia and Ecdysozoa. The groups under deuterostomia include Echinoderms, Chordates, Hemichordates, and other higher and more complex organisms like human beings.
Characteristics of Deuterostomes
the blastopore Develops into an anal
The mouth in deuterostomes is formed by the gut that tunnels to the embryo
Deuterostomes are Always enterococcus.
The nervous system of deuterostomes is composed of the hollow nerve cord
the body Composition is more complex as compared to protostomes
During the development phase, they go through the intermediate tree cleavage where all the Blastoma can develop into the embryos completely
Here, the animals undergo Radical cleavage
deuterostomes contain fewer phyla and species as compared to protostomes
echinoderms, hemichordates and chordates are Included in deuterostomes
For deuterostomes, Early stages of embryo formation, archenteron development takes place.
Characteristics of Protostomes
The blastopore develops into a mouth and not the anus
Bigot tunnels into an embryo and forms the anus
The Nervous System of protostomes is solid and has a ventral solid COD
Organisms of protostomes undergo determinate cleavage.
The blastopore produced in the development stages of the embryo cannot develop.
Spiral cleavage is exhibited by protostomes
Protostomes are Less evolved and more Complex than deuterostomes
There is No archenteron development
The anus arises at a secondary position
Organisms of protostomes include flatworms annelids and Arthropods
protostomes have multi ciliated cells
Subject Difficulty Level
Biology is a comparatively difficult subject than the other sections of science, due to its complexity and diversity in concepts.
However, with firm dedication and determination, all the topics can be easily tackled.
It is not to be ignored that Biology plays an important role and has a heavier weightage as compared to the other sections of science subject
Relatively more marks can be scored through Biology subject if studied thoroughly
Learning biological topics may require a lot of time at the initial stages, but once the concept is understood only regulated revision is required to Remember.
The most important tip in learning Biology is to make notes.
Always remember to make proper important notes while studying and duly revise them repeatedly so that all The detailed data is being remembered by the brain.
This topic is simple and hence cannot be neglected for studying purpose
Reproduction in Deuterostomes and Protostomes
The most common deuterostomes have separate sexes. This means the male and females are indifferent organisms of deuterostomes. So the most common method of reproduction of deuterostomes is sexual reproduction. However, there are some exceptions such as ascidians.
As protostomes fall in the higher category of animals, they reproduce sexually. They form gametes in the form of sperms for male systems and oocytes for female systems. Major protosomes are gonochoristic that is they have separate male and female individuals.
Points to Remember
deuterostomes and protostomes are two groups of coelomates
deuterostomes And protostomes are differentiated based on their formation and cleavage during the development phase
The distinction between deuterostomes and protostomes is that in deuterostomes blastopores develop into anal opening and in protostomes, blastopores develop into a mouth
protosomes are invertebrates whereas deuterostomes Have chordates
In protostomes, the mouth forms before the anus
whereas in deuterostomes the anus is formed before the formation of the mouth
Samples Questions for Exam
What are deuterostomes explain their properties?
What are protostomes and explain their properties?
Differentiate between deuterostomes and protostomes.
What are the characteristics of deuterostomes?
Advantages of being deuterostomes over protostomes.
For more concepts, access the free resources available on the Vedantu website and enjoy learning!
FAQs on Difference Between Protostomes and Deuterostomes
1. What do the Terms Gastrulation, Archenteron, and Blastopore Mean?
In most animals, gastrulation is an early phase of embryonic development when the simple spherical ball of cells called the blastula undergoes extensive cell movements and reorganisation to develop into a multi-layered structure called the gastrula. During gastrulation, the three primary germ layers, that is, the ectoderm, endoderm, and the mesoderm are formed and organised into their appropriate locations.
When a developing embryo undergoes gastrulation, a primary gut or digestive tube is formed which is known as the archenteron. The archenteron later develops into the endoderm and mesoderm.
Blastopore is an opening of the gastrula through which the latter communicates with the outside. The blastopore develops into the mouth or the anus during maturation of most animals. In others, the blastopore serves as the canal joining the neural tube (primitive nervous system) to the primitive gut.
2. What are Diploblastic and Triploblastic Animals?
Diploblastic and triploblastic are two different stages in blastula formation. The germ layer is the primary layer of cells formed during embryogenesis. In vertebrates, gastrulation usually gives rise to three germ layers: endoderm, mesoderm, and ectoderm. Eumetazoans or animals with a more complex structure than sponges produce two to three germ layers. Diploblastic animals produce only two germ layers - endoderm and ectoderm (example: radially symmetrical animals like starfish). Triploblastic animals produce all the three germ layers, that is, ectoderm, endoderm, and mesoderm. Animals that are bilaterally symmetrical, such as humans, are triploblastic. Hence, the key difference between diploblastic and triploblastic animals is that diploblasts produce two germ layers (excluding the mesoderm) and triploblasts produce all the three germ layers.
3. What is the significance of Deuterostomes?
Deuterostomes are animals in which the anus is formed first before the mouth during their embryological development. These animals are drawn towards the environment, because of their importance in natural and human ecosystems. They are key predators and herbivores in most terrestrial Habitats. Deuterostomes are packed with yolk protein so that the Development of the embryo is started before the hatching period. This provides the energy for the mother to develop the embryo into the adult during the development process.
4. Are humans Deuterostomes or Protostomes?
deuterostomes are the animals in which the anus is formed before the mouth in their embryological development. Humans are deuterostomes as the development of humans starts with an embryo. And anus is formed Before any other opening. So humans have both mouth and anus which is the next common property of deuterostomes. Humans even have a nerve cord which deuterostomes also do have.
5. What is the main characteristic Deuterostomes and Protostomes share?
In deuterostomes, the formation of the anus takes place earlier than the mouth whereas in protostomes the mouth is formed before the anus. Both deuterostomes and protostomes have a blastopore during coelom formation that is during the formation of a hollow sphere. these are the types of cell development in the body. And in both the cells there is a coelom (body cavity), an archenteron (developing digestive tube), a mesoderm (middle germ layer) and a digestive tube present. To get to the 8 cell stage, they both need to go through the cleavage. Both deuterostomes and protostomes belong to the kingdom Animalia.
