Protostome vs. Deuterostome: What is the difference between Protostome and Deuterostome?

Protostome vs. Deuterostome: are two kinds of classifications used for the complex animals based on their embryonic developments. The major difference between the two lies in the development of blastopore, the first opening of an animal’s embryo. The opening becomes the mouth in the case of the protostome and anus in the case of the deuterostome.

Understanding the meaning of protostome and deuterostome in detail

To mark a clear distinction between the two, we need to look at their in-depth meaning. 

What is Protostome in biology?

‘Proto’ in Greek translates to first while ‘stoma’ translates to mouth, thereby protostome, in a literal sense, means ‘the first mouth’. When the first opening of an animal’s embryo develops into a mouth, the animal is classified as a protostome. Examples include insects and earthworms.

What is Deuterostome? 

‘Deutero’ in Greek translates to second, thereby, deuterostome translating to ‘second mouth’. When the first opening of an animal’s embryo develops into the anus, the animal is classified as a deuterostome. The examples include humans and starfish.

Considering the similarities between protostome vs. deuterostome

  • Both protostome and deuterostome are a part of the group Bilateria.
  • They are the classifications used for complex animals.
  • Both protostome and deuterostome are coelomates and possess a true coelom.
  • They develop a completely functioning alimentary canal.
  • The classification of animals into protostome and deuterostome helps the biologists to determine the relationship between different species and their development. 
  • Both the words protostome and deuterostome are derived from the Greek language.

Top 7 Differences Between Protostomes and Deuterostomes with Examples

The protostome and deuterostome differences can better help you understand the whole concept. Let us find them here:

Formation of blastoporeThe blastopore forms the mouth in a protostome.The blastopore forms the anal opening in a deuterostome.
Nervous systemTheir nervous system consists of a ventral nerve cord that is solid from inside.Their nervous system consists of a hollow nerve cord.
Mesoderm formationThe mesoderm forms with the migration of the Mesenchymal cells.The mesoderm in deuterostome forms from the ingrowths of the archenteron. 
Zygote cleavageThe zygote cleavage in the protostome is considered determinate and spiral. The four embryo cells experience an oblique cleavage and the fate of resultant cells is determined.The zygote cleavage in the protostome is indeterminate and radial. The four embryo cells experience a perpendicular and parallel cleavage to the body axis and the fate of resultant cells is not determined.
Origin of coelomThe solid mesoderm masses split to develop coelom in a protostome. This splitting process is known as Schizocoelous.The archenteron fold develops coelom in a deuterostome in the form of a pair of primitive gut’s mesodermal pouches. The process is known as Enterocoelous.
Ciliary bandsThe larval ciliary bands of protostomes have multi-ciliated cells.The larval ciliary bands of deuterostomes carry single cilium per cell.
PhylaArthropoda, Annelida, and Mollusca phyla are classified as protostomes.Chordata, Echinodermata, and Hemichordata phyla are classified as deuterostomes.
ExamplesInsects, squid, and snails are some organisms considered as protostomes.Humans, sea urchins, and starfish are some organisms considered as deuterostomes.

Are humans Deuterostome or Protostome?

Humans are considered Deuterostome as their blastopore aka primitive streak, the closest analogous component in the case of human embryos, forms anus of the digestive tract. The mouth forms at a much later stage.

What are the advantages of deuterostomes?

Comparing protostome vs. deuterostome development, none of them have an advantage over the other. But looking at these organisms together, both protostomes and deuterostomes have the advantage of possessing two separate openings for consuming food and passing out feces. This ensures to make the process easier in the case of complex animals as the gut, that joins these two openings, helps in the absorption of nutrients for the whole body.

Are invertebrates Protostomes or Deuterostomes?

The primitive invertebrates are protostomes whereas chordates, echinoderms, and hemichordates are deuterostomes.

Are Cnidaria Protostomes or Deuterostomes?

Cnidaria is considered neither a protostome or a deuterostome and not included in the group Bilateria that classified animals into protostomes and deuterostomes. Cnidaria is considered as simpler organisms and, therefore, included in the group Radiata.

Are Frogs protostomes or deuterostomes?

Frogs are deuterostomes as they are a part of phylum Chordata. The first opening of a frog’s embryo develops into the mouth while the anal opening is formed at a later stage of embryo development.

Are jellyfish Protostomes?

Jellyfish is a commonly-used name for several gelatinous species that are a part of phylum Cnidaria. Therefore, they are neither protosomes nor deuterostomes like other Cnidaria members.

Which phylum are deuterostomes and protostomes?

The phyla Chordata, Echinodermata, and Hemichordata forms part of deuterostomes while the phyla Arthropoda, Annelida, and Mollusca form part of protostomes.

Have deuterostomes originated from protostomes?

No, neither deuterostomes originated from protostomes nor the protostomes originated from deuterostomes. They originated individually from common ancestors that lead to similarities between them.

Do all Deuterostomes have a Coelom?

Yes, all deuterostomes have coelom that develops via the Enterocoelous process.

Are snails Deuterostomes?

No, snails are protostomes as they are a part of phylum Mollusca that encompasses protostome coelomates. The blastopore develops into the mouth in the case of snails.

What forms the mouth in a Deuterostome?

The mouth is formed gradually in the case of deuterostomes. The blastopore does not develop into the mouth in the case of a deuterostome rather the mouth of the organism forms at the other end of the embryo that lies opposite to the blastopore.

Do cnidarians have Protostome development?

No, cnidarians do not have protostome development. That does not also mean that cnidarians are deuterostome. They are neither of them. They are a part of a completely different group Radiata that does not classify animals as protostomes and deuterostomes.

Comparison Chart

Protostome vs. Deuterostome: Let’s discover their differences, similarities, examples, and answer some of the most frequently asked questions (FAQ) about Protostome and Deuterostome

Comparison Video

Protostomes vs. Deuterostomes | ZooLea | Lesson 14 | Biology (Zoology)

The Bottom Line

Though both protostome and deuterostome are a part of the same group Bilateria, they are extremely different in terms of the embryo development process they experience. Considering protostome vs. deuterostome, the blastopore forms the animal’s mouth in the former case while it forms the animal’s anal opening in the latter.

Author & Researcher @ Difference 101 Master in Philosophy & Data Analysis, Sorbonne Université (Graduated 2011) Lived in New York City

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