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Related to Protostomia: Deuterostomia


Any of numerous invertebrate animals of the group Protostomia, in which the mouth develops from the first opening in the embryo and the anus develops later, and including the mollusks, annelids, and arthropods.

[From New Latin Prōtostomia, taxon name : proto- + New Latin stoma; see stoma.]
American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.


(Zoology) a mollusc, annelid, arthropod or other animal in which the mouth develops before the anus at embryonic stage
Collins English Dictionary – Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014


(ˈproʊ təˌstoʊm)

any invertebrate 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.
Random House Kernerman Webster's College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.
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The spiral cleavage, musculature (Slyusarev and Starunov, 2016), and fine structure of ciliated cells and ciliary rootlets (Slyusarev and Kristensen, 2003) of Orthonectida show similarities to those of annelids; therefore, it has been suggested that they be a member of the Protostomia. Molecular phylogenetic analyses have been in accord with this view (Hanelt et al., 1996; Pawlowski et al., 1996; Petrov et al, 2010), with genomic data of Intoshia linei strongly supporting this affinity (Mikhailov et al., 2016).
Natura--nature Mundus Plinius--physical world naturalia--natural bodies Biota Domain Eukaryota Chatton, 1925--eukaryotes Kingdom Animalia Linnaeus, 1758 --animals Eumetazoa Butschli, 1910--eumetazoans Bilateria Hatschek, 1888-- bilaterians Eubilateria Ax, 1987 Protostomia Grobben, 1908 Lophotrochozoa K.M.
(2009) Caenorhabditis elegans galectins LEC-6 and LEC-1 recognizes a chemically synthesized GalO1-4Fuc disaccharide unit which is present in Protostomia glycoconjugates.
Likewise, no proteins similar to SC proteins were found in Tardigrada and Onychophora (Protostomia) and in Hyperotreti, Hyperoartia, and Chondrichthyes (Chordata).
However, to date, only the Dmrt-like protein from the Pacific oyster (Crassostrea gigas) has been cloned and studied in the Protostomia Lophotrochozoa phylum (Naimi et al.