Protostomia


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Related to Protostomia: Deuterostomia

Protostomia

[‚prōd·ə′stō·mē·ə]
(invertebrate zoology)
A major division of bilateral animals; includes most worms, arthropods, and mollusks.

Protostomia

 

a group of invertebrates, including Plathel-minthes, Nemathelminthes, Nemertini, Annelides, Mollusca, and Arthropoda. Protostomes are bilaterally symmetrical animals. Their development is characterized by the formation of a mouth from the primitive blastopore or from its anterior part. The anal opening emerges from the posterior part of the body. There is an exoskeleton of cuticle, chitin, or shell. The foregut and hindgut develop by invagination of the ectoderm. Blastulation is spiral unless it has undergone a secondary change.

References in periodicals archive ?
Gangliosides have never been identified in the phylum of protostomia, though the presence of polysialic acid was shown in the embryos of Drosophila.
It was found that the outer arm dynein purified biochemically from oyster, as a representative of Protostomia, (187) and that of sea anemone (Cnidaria) (6) situated at the root of two main branches of the phylogenetic tree also consist of two heavy chains.
(1992) Dynein of sperm flagella of oyster belonging to Protostomia also has a two-headed structure.
For more than a century, the Bilateria have traditionally been divided into Protostomia and Deuterostomia (or through a misinterpretation of Hyman, 1951, into Acoelo-mata, Pseudocoelomata, and Eucoelomata.
Therefore, specification of differentiation fate along the anterior-posterior axis by Hox genes need not have evolved independently in Protostomia and Deuterostomia, as required under Nielsen's rendition of the larval-first hypothesis.