Protostomes Vs. Deuterostomes: 14 Major Differences With Examples

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What Are Deuterostomes And Protostomes?

Deuterostomes are the animals whose embryonic development undergoes radial cleavage. In other words, the cell division planes take place radially during the formation of the blastula through cleavage of the fertilized egg embryo. In deuterostomes, the first cavity formed by the blastopore ends up as the organism’s anus, while the mouth is formed secondarily on the opposite side. The deuterostomes can be grouped taxonomically into the following clades:

  • Echinodermata e.g starfish, sea urchin, crinoids, sea cucumber, blastoid, cystoidea, Eocrinoidea etc.
  • Chordates include marine and terrestrial animals (mammals, reptiles, amphibians, frog, turtle, lizard, bat, tetrapods, Sloth, and jawless fish).
  • Cephalochordata  e.g lancelets
  • Urochordata which includes tunicates (sea squirts), Ascidians, Larvacea, Thaliacea etc.
  • Vertebrata
  • Hemichordata e.g planctosphaeroidea, graptolithina, pterobranchia, acorn worm

Protostomes is any member of the lower invertebrate phyla in which the mouth appears before the anus during development, cleavage is spiral and determinate and the coelom forms as a splitting of the mesoderm.  Examples of protostomes include:

  • Leeches
  • Insects (beetles, ants, flies, crickets, butterflies, flees, cicada, bees)
  • Spiders
  • Crustaceans (crabs, lobsters, crayfish, woodlice, bernacles)
  • Velvet worms
  • Centipedes and millipedes
  • Earthworms
  • Squid
  • Octopus
  • Snail and slugs
  • Bivalve mollusks (clams, oysters, mussels, scallops)

The main difference between protostomes and deuterostomes is at the point of the blastopore. In protostomes, the blastopore develops into the mouth and the opposite cavity develops into the anus. In deuterostomes (the group that includes vertebrates and echinoderms), the blastopore develops into anus. Below, get to understand more differences between deuterostomes and protostomes.

Also Read: Difference Between Phytoplanktons and Zooplanktons

Characteristics Of Protostomes

  • The blastopore in a protostome develops into a mouth.
  • Protostomes are referred to as schizocoelomates because the coelom is developed by splitting of the solid mass of the embryonic mesoderm.
  • In protostomes, the gut is tunneled into embryo and forms anus.
  • There is no archenteron development in protostomes. Archenteron is a rudimentary alimentary cavity formed during the early stages of embryo development. It usually develops into mosederm and endoderm of a living organism.
  • Protostomes can be priapulids.
  • The nervous system of protostomes is solid, ventral nerve cord. It is also important to note that many deuterostomes also have pharyngeal gill slits.
  • Protostomes are less evolved and complex in their body compositions than Deuterostomes.
  • Protostomes are multi-ciliated cells.
  • All the remaining bilaterian phyla are grouped into protostomes or divided into two groups:  protostomes and lophophorate.
  • Protostomes contains less phyla and species than Deuterostomes.
  • In protostomes, the anus arises secondarily.
  • Protostomes exhibit determinate cleavage. Determinate cleavage is whereby the blastomere produced in the early stages of embryo development do not have capacity to develop into independent embryos.
  • Protostomes undergo spiral cleavage. In spiral cleavage, the blastomeres of the animal pole are rotated with respect to those of the vegetal poles.
  • Protostomes include flat worms, annelids, arthropods, mollusks and other less complex organisms.

Characteristics Of Deuterostomes

  • The blastopore in deuterostomes develops into an anal opening.
  • Deuterostomes are referred to as enterocoelous because the longitudinal pouches of the archenteron forms the coelom.
  • In deuterostomes , the mouth is formed by gut being tunneled into embryo.
  • Deuterostomes have archenteron development in the early stages of embryo formation.
  • Deuterostomes are always enterocoelous.
  • The nervous system of deuterostomes is composed of hollow nerve cord.
  •  Deuterostomes are more evolved and complex in their body compositions than protostomes.
  • Deuterostomes are all mono-cliated.
  • Deuterostomes mainly includes echinoderms, hemichordes and chordates
  • Deuterostomes contains less phyla and species than protostomes.
  • In deuterostomes, the mouth arises secondarily.
  • Deuterostomes exhibit indeterminate cleavage. Indeterminate cleavage is whereby all early blastomeres have the capacity to develop into a complete embryo.
  • Deuterostomes undergo radial cleavage. In radial cleavage, the blastomeres of upper tiers are positions directly above those of lower tiers. This eventually results in radial symmetry across animal pole and vegetal pole.
  • Deuterostomes include chordates, echinoderms, pogonophora, hemichordates and other higher and complex organisms. Deuterostomes includes higher animals like human beings, monkeys, birds etc.

Also Read: Difference Between Amphibian And Reptile

Protostomes Vs. Deuterostomes In Tabular Form

BASIS OF COMPARISON   DEUTEROSTOMES PROTOSTOMES
Blastopore Blastopore in deuterostomes develops into an anal opening.   The blastopore in a protostome develops into a mouth.  
Coelom They are referred to as enterocoelous because the longitudinal pouches of the archenteron forms the coelom. They are referred to as schizocoelomates because the coelom is developed by splitting of the solid mass of the embryonic mesoderm.  
Mouth & Anus The mouth is formed by gut being tunneled into embryo.   The gut is tunneled into embryo and forms anus.  
Archenteron Have archenteron development in the early stages of embryo formation.  There is no archenteron development.
Nature They are always enteroceolus.   They can be priapulids. 
Nervous System The nervous system is composed of hollow nerve cord and pharyngeal gill slits.   The nervous system is solid, ventral nerve cord.
Evolution They are more evolved and complex in their body compositions.   They are less evolved and simple in their body compositions.  
Cell Ciliation They are all mono-ciliated.   They are multi-ciliated cells.
Division They mainly include echinoderms, hemichordes and chordates   All the remaining bilaterian phyla are grouped into protostomes or are divided into two groups:  protostomes and lophophorate.
Number Of Phyla Deuterostomes contains less phyla and species than protostomes.    
Anus & Mouth Development The mouth arises secondarily. The anus arises secondarily.  
Cleavage Exhibit indeterminate cleavage.   Exhibit determinate cleavage.
Cleavage Shape Undergoes radial cleavage. Undergoes spiral cleavage.  
Examples Chordates, Echinoderms Pogonophora, Hemichordates and other higher and complex organisms. Flat worms, Annelids, Arthropods, Mollusks and other less complex organisms.

Also Read: Difference Between Chordates And Non-Chordates

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