protostome

American  

[proh-tuh-stohm] / ˈproʊ təˌstoʊm /

noun

Zoology.

1. 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.

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protostome Scientific  

/ prōt′tə-stōm′ /

1. Any of a major group of animals defined by its embryonic development, in which the first opening in the embryo becomes the mouth. At this stage of development, the later specialization of any given embryonic cell has already been determined. Protostomes are one of the two groups of animals having a true body cavity (coelom) and are believed to share a common ancestor. They include the mollusks, annelids, and arthropods.

2. Compare deuterostome

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Etymology

Origin of protostome

proto- + -stome

Compare meaning

How does protostome compare to similar and commonly confused words? Explore the most common comparisons:

• protostome vs. deuterostome

Example Sentences

Since these genes are not clustered in available protostome genomes, there is no evidence for deeper bilaterian ancestry.

From Nature • Nov. 17, 2015

As the protostome develops, the mesoderm grows and fuses with the gastrula cell layer.

From Textbooks • Jan. 1, 2015

The body plan of the deuterostome at this stage looks very similar to that of the protostome, but the blastopore becomes the anus, and the second opening becomes the mouth.

From Textbooks • Jan. 1, 2015

This discovery allowed for the distinction of the protostome clade, the lophotrochozoans.

From Textbooks • Jan. 1, 2015