What are the key differences between protostomes and deuterostomes in embryonic development and body plan
In biology, embryonic development is classified into two kinds on the basis of the complex animals and can be given as deuterostomes and protostomes. One of the major differences seen in both the development types is the development of blastopore which is also the first opening of the animal’s embryo. The opening can either be the mouth as in the case of protostomes or it can be anus as in the case of deuterostomes. To know more about the Differences Between Protostomes and Deuterostomes here is a detailed guide via Vedantu that lets you know regarding the same.
Deuterostomes
The embryonic development of deuterostomes goes through radial cleavage. While the blastula is forming via cleavage of the embryo, the cell division process occurs in radial. In this group of animals, the initial cavity created by the blastopore matures as the anus of the organism. Also, the mouth of the concerned organism is created on the other side after the formation of the anus.
Based on the similarities of structure, the following clades of deuterostomes animals are available-
Echinodermata
Echinodermata is exclusively identified as marine animals. The adult echinoderms are recognisable by the radial symmetry.
Example: Sea cucumbers, Starfish, Sand dollars, Sea lilies, etc.
Chordates
It includes both terrestrial and marine animals.
Example: Frog, Tiger, Bat, Turtle, Snake, Jawless fish, etc.
Cephalochordata
They are small marine organisms with segmented bodies.
Example: Lancelets.
Urochordata
They are also sea animals and known as Tunicata.
Example: Sea squirts, Thaliacea, Ascidians, Larvacea, etc.
Vertebrata
It includes all animals that fall under subphylum vertebrates.
Example: humans, Birds, Amphibians, Fish, etc.
Hemichordata
Hemichordata is a marine species and can be grouped as sister organisms of echinoderms.
Example: Graptolithina, Acorn worm, Pterobranchia, etc.
Protostomes
include the lower invertebrate species in which the formation of the mouth happens before the creation of the anus during embryo development. These animals have determinate and spiral cleavage and through the dividing of mesoderm their coelom forms.
Some examples of protostomes are octopuses, squid, snail, centipedes, millipedes, spiders, butterflies, ants, bees, earthworms, clams, oysters, etc.
Thus, the fundamental difference between protostomes and deuterostomes animals is the conversion of blastopore into the mouth or anus.
Differences between Protostomes and Deuterostomes
Thus, the difference between protostomes and deuterostomes lies in the position of their organs. In deuterostomes, the blastopore transforms into an anus, and another cavity on the opposite side creates a mouth. However, in protostomes, the mouth is created from the blastopore.
To learn about the difference between protostomes and deuterostomes in-depth, go through the study materials available on Vedantu’s website. For quick learning, download our Vedantu app.
Cleavage Types are Seen in Both Deuterostomes and Protostomes
The two classes differ entirely in the types of cleavages that they undergo while the formation of blastopore takes place. The cleavage that is seen can be of two types:
Determinate cleavage is also called mosaic cleavage
indeterminate cleavage is called regulative cleavage.
1. Protostomes:
These undergo the determinate type of cleavage during the formation of the blastopore. During this type of cleavage, the developmental fate of cells is already determined during the early stages of the embryo.
2. Deuterostomes:
Deuterostomes on the other hand have an indeterminate type of blastomere cleavage. In this type, the fate of the cells is not set and will only be decided after each cell is formed. It is also seen that any of the cells present in the blastopore has an equal potency to become any of the cell types that the cell wants to be. This condition is specifically called the pluripotency of the cells where each cell can undergo a different function.
Characteristics of Protostomes:
Protostomes are also referred to as schizocoelomates as the coelom is developed by splitting the solid mass of embryonic mesoderm
In protostomes, the gut is tunnelled through the embryo and it reaches up to the anus
Protostomes are said to be multi-ciliated cells.
FAQs on Differences Between Protostomes and Deuterostomes in Animal Development
1. What is the difference between protostomes and deuterostomes?
The main difference between protostomes and deuterostomes lies in their embryonic development, especially how the blastopore and body cavity form.
- In protostomes, the blastopore develops into the mouth.
- In deuterostomes, the blastopore develops into the anus, and the mouth forms later.
- Protostomes usually show spiral cleavage and schizocoelous coelom formation.
- Deuterostomes typically show radial cleavage and enterocoelous coelom formation.
2. What are protostomes?
Protostomes are animals in which the blastopore develops into the mouth during early embryonic development.
- They exhibit spiral and determinate cleavage.
- The coelom forms by splitting of mesoderm, called schizocoely.
- Most belong to the clade Protostomia.
- Examples include arthropods (insects, crabs), mollusks (snails, octopus), and annelids (earthworms).
3. What are deuterostomes?
Deuterostomes are animals in which the blastopore develops into the anus, and the mouth forms secondarily.
- They show radial and indeterminate cleavage.
- The coelom forms by outpocketing of the archenteron, called enterocoely.
- They belong to the clade Deuterostomia.
- Examples include echinoderms (starfish, sea urchins) and chordates (fish, birds, mammals).
4. How does cleavage differ in protostomes and deuterostomes?
Cleavage in protostomes is typically spiral and determinate, while in deuterostomes it is radial and indeterminate.
- Spiral cleavage: Cells divide at oblique angles, creating a spiral arrangement.
- Determinate cleavage: Each embryonic cell has a fixed fate early in development.
- Radial cleavage: Cells divide parallel or perpendicular to the axis, forming symmetrical tiers.
- Indeterminate cleavage: Early cells can develop into a complete embryo (basis of identical twins in humans).
5. What is schizocoelous and enterocoelous coelom formation?
Schizocoelous and enterocoelous refer to two different methods of coelom formation in embryonic development.
- Schizocoely (protostomes): The mesoderm splits internally to form the coelom.
- Enterocoely (deuterostomes): The coelom forms from pouch-like outgrowths of the archenteron.
6. What are examples of protostomes and deuterostomes?
Protostomes include arthropods, mollusks, and annelids, while deuterostomes include echinoderms and chordates.
- Protostomes: Insects, spiders, crabs, snails, clams, earthworms.
- Deuterostomes: Starfish, sea urchins, fish, amphibians, reptiles, birds, mammals.
7. Why is the blastopore important in distinguishing protostomes and deuterostomes?
The fate of the blastopore is important because it determines whether an animal is a protostome or a deuterostome.
- In protostomes, the blastopore becomes the mouth.
- In deuterostomes, the blastopore becomes the anus.
8. Are humans protostomes or deuterostomes?
Humans are deuterostomes because the blastopore develops into the anus during embryonic development.
- Humans belong to the phylum Chordata.
- They exhibit radial, indeterminate cleavage.
- The coelom forms through enterocoely.
9. Do protostomes and deuterostomes differ in nervous system development?
Yes, protostomes typically have a ventral nerve cord, while deuterostomes generally have a dorsal nerve cord.
- Protostomes: Nervous system usually located ventrally (e.g., insects, annelids).
- Deuterostomes: In chordates, the dorsal hollow nerve cord develops into the brain and spinal cord.
10. Why are protostomes and deuterostomes important in evolutionary biology?
Protostomes and deuterostomes are important because they represent two major evolutionary lineages of bilaterally symmetrical animals.
- They belong to the group Bilateria.
- Their developmental differences reflect early evolutionary divergence.
- Comparing them helps scientists understand the evolution of body plans, organ systems, and symmetry.
