Protostomia (Protostomes) and Deuterostomia (Deuterostomes) are two animal petals that makeup Bilateria, subkingdom calyx: Eumetazoa, which consists of animals consisting of bilateral symmetry and three layers of germs.

The main difference between protostomes and deuterostomes comes from the development of their blastopore, the temporary opening of the archenteron to the outside of the embryo at the gastrula stage, which is related to the development of the mouth or the next anal opening.

The main difference between protostomes and deuterostomes is in protostomes, blastopore develops into the mouth whereas, in deuterostomes, blastopore is developed into an anal opening. Both Protostomia and Deuterostomia form clades: Nephrozoa.

Definition of Protostomia

Protostome (from Greece: first mouth) is one of the clad animals. Together with deuterostomia and several small phyla, protostomia forms Bilateria, which consists mainly of animals with bilateral symmetry and three layers of germplasm. The main difference between deuterostomia and protostomia lies in the development of the embryo.

In animals that are at least as complex as earthworms, the embryo forms an indentation (blastopore) on one side, which continues to bend to form archenteron, the first phase of the digestive tract growth. In deuterostomia, the original curve becomes anus while the digestive tract then forms another hole, which forms the mouth. Protostomia is so named because it was once thought that in their embryos, indentations formed the mouth while the anus formed later, in holes made from the other end of the digestive tract. However, recent research shows that in protostomia, the edges of the curve are closer to the center, making holes in the ends that become the mouth and anus.

However, this idea was challenged, because Platyhelminthes, a group that forms a sister group of other bilaterian animals, has one mouth without anus. The genes used in the embryonic construction of the mouth are the same as those expressed around the mouth of the protostomia.
There are other significant differences between the patterns of development of protostomia and deuterostomia:

  • Most protostomia is a schizocoelomata, which means a solid mass of embryonic mesoderm is divided then forms a coelom. Some, like Priapulida, do not have a coelom, but they may be descended from schizocoelomata ancestors. On the other hand, all known deuterostomia are enterococci, which means that the coelom is formed from a transverse sac from the archenteron which then becomes a separate cavity.
  • In protostomia, some phyla experience what is called the decisive spiral cleavage, which is what cells will be determined when they are formed. This contrasts with deuterostomia which has an unspecified radial division.

Molecular data currently gives clues that animal protostomia can be divided into three main groups:

  • Ecdysozoa, for example, arthropods, nematodes
  • Platyzoa, for example, Platyhelminthes, rotifers
  • Lophotrochozoa, examples of mollusks, annelids

Scientific Classification

  • Kingdom: Animalia
  • Clade: ParaHoxozoa
  • Clade: Bilateria
  • Clade: Nephrozoa
  • (unranked): Protostomia

(Grobben, 1908)


  • Ecdysozoa
  • Spiralia
  • Chaetognatha

Definition of Deuterostomia

Deuterostome (from Greek: second mouth) is an animal super film. they are a subtaxon of the Bilateria branch of the Eumetazoa subregnum, and an opponent of Protostomia. Deuterostomia is different because of its embryonic development; in deuterostomia, the first hole of the blastopore becomes the anus, whereas in protostomia the hole becomes the mouth.

There are four living deuterostomic phyla:

  • Filum Chordata (vertebrates and their relatives)
  • Filum Echinoderms (starfish, sea urchins, sea cucumbers, etc.)
  • Filum Hemichordata (Acorn worm and possibly graptolite)
  • Filum Xenoturbellida (2 species of worm-like animals)

The phylum Chaetognatha (arrowworm) may also be included here. The group that has become extinct may be Vetulicolia. Echinoderms, Hemichordata and Xenoturbellida form the Ambulacraria class.

Both deuterostomia and protostomia, the first zygote forms hollow ball cells called blastulas. In deuterostomia, the initial division occurs parallel or perpendicular to the polar axis. This is called radial fission, and also occurs in some protostomia such as Lophophora. Many deuterostomia show an indeterminate division, which will be what a cell is not determined by the identity of the stem cell. Therefore if the first 4 cells are separated, each cell can form complete larvae, and also a cell is removed from the blastula, other cells will replace it.

In deuterostomia, mesoderm is formed as a developing bowel bulge that separates, forming a body cavity (coelom). This is called enterococci.
Hemichordata and Chordata have gill slits, and primitive echinoderm fossils also show gill slits. Deep nerve cords are found in all chordates, including the Tunicata (at the larval stage).

Some hemichordates also have tubular nerve cords. In the early stages of the embryo, it looks like a chordate nerve cord. Because the degenerated echinoderm nervous system is not possible to know much about their ancestors in this way but based on other facts it is still possible that all duterostomia now evolved from a common ancestor that has gill slits, deep nerve cords, and segmented bodies. It may resemble a small group of deuterostomian Cambrian Vetulicolia.

Scientific Classificatione

  • (unranked): Filozoa
  • Kingdom: Animalia
  • Subkingdom: Eumetazoa
  • Clade: ParaHoxozoa
  • Clade: Bilateria
  • Clade: Nephrozoa
  • Superphylum: Deuterostomia

(Grobben, 1908)


  • Chordata
  • Saccorhytida †
  • Ambulacraria (?)

Difference Between Protostomia and Deuterostomia

Difference Between Protostomia and Deuterostomia
resource: schoolbag.info

Blastopore Development

  • Protostomia: Blastopore develops into the mouth.
  • Deuterostomiaa: The blastopore develops into the anal canal.

The origin of Mesoderm

  • Protostomia: No development of archenteron in protostomes.
  • Deuterostomia: Early development of the intestine is called archenteron in deuterostomes.

Intestinal Development

  • Protostomia: Intestines are inserted into the embryo to form the anus.
  • Deuterostomiaus: Intestines are inserted into the embryo to form the mouth.

Coelom Development

  • Protostomia: Protostomia is called schizocoelomates because the coelom is developed by the separation of embryonic mesodermic solid masses.
  • Deuterostomia: Deuterostomia is called enterocele because the longitudinal pockets of the archenteron form a coelom.

Cleavage Type

  • Protostomia: Protostomia shows the determinants of division.
  • Deuterostomiaa: Deuterostomiaa shows an indeterminate division.

Types of Holoblastic Cleavage

  • Protostomia: Protostomia experiences a spiral division.
  • Deuterostomia: Deuterostomia experiences radial division.

Nervous system

  • Protostomia: Protostomia consists of solid ventral nerve cables.
  • Deuterostomiaa: Deuterostorms consist of hollow nerve cords and pharyngeal gill slits.


Protostomia develops the mouth from blastopore during embryonic development. On the other hand, deuterostomes develops the anus from the blastopore. Both protostomes and deuterostomes also consist of differences in the development of their three germ layers. Deuterostomiaa contains a higher modified nervous and muscle system. The main difference between protostomes and deuterostomes

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