BIOG 1105-1106 | Autotutorial Introductory Biology

Labs

Labs

Protostomes vs. Deuterostomes

What is a deuterostome?

All bilateral animals can be divided into two groups. The deuterostomes, a group that includes echinoderms, hemichordates, and chordates, and the protostomes, a group that includes annelids, arthropods, molluscs, and many other invertebrate taxa. The deuterostomes can be distinguished from protostomes by a number of features of their embryology.
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The fate of the blastopore is a key characteristic that distinguishes protostomes from deuterostomes.

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Deuterostomes can be distinguished from protostomes by several aspects of their embryology.

Cleavage
- Protostomes - spiral, determinate cleavage in which cleavage furrows are offset and the developmental "fate" of a given cell is determined relatively early.
- Deuterostomes - radial, indeterminate cleavage in which cleavage furrows are aligned and developmental "fate" is determined later.
Coelom Formation
- Protostomes - schizocoelous - meaning that the body cavity (coelom) forms when masses of mesoderm split.
- Deuterostomes - enterocoelous - meaning that the body cavity (coelom) forms from infoldings of the primitive gut.
Fate of the Blastopore
- Protostomes - protostome means "first mouth", referring to the fact that the blastopore becomes the mouth.
- Deuterostomes - deuterostome means "second mouth", referring to the fact that the blastopore becomes the anus and the mouth forms from a separate invagination (see below).