The four new laboratory sequences (Mga lab, Oed lab, Sma lab, and Vpu lab) presented three residues that are characteristic of PG-1 proteins in deuterostomes and
protostomes, Ala29, Asn41, and Thr43 (Fig.
Likewise, deuterostomes have their heart on the ventral side, while
protostomes have it on the dorsal side.
In N-linked saccharide chains of species belonging to
protostomes (nematode, squid, and limpets, etc.
However, nemerteans, or "ribbon worms," belong to their own phylum of about 1300 species in the lophotrochozoan clade of
protostomes that includes molluscs and annelids, whereas nematodes and related invertebrates such as arthropods constitute separate phyla of ecdysozoan
protostomes (Kajihara et al.
The same collagen-proteoglycan-adhesive glycoprotein ECM is found in both
protostomes and deuterostomes.
Testing the new animal phylogeny: first use of combined large-subunit and small-subunit rRNA gene sequences to classify the
protostomes.
Finally, we examined representative metazoan genomes and found highly conserved usherin genes throughout the deuterostome lineage as well as in some
protostomes.
Based on the lack of homology between the postoral ciliated bands and on recent phylogenies of
protostomes and polychaetes, a broader definition of trochophore is more likely to reflect the plesi-omorphic condition: a larva with a preoral ciliated band derived from trochoblasts (prototroch) (Damen and Dictus, 1994; Rouse, 1999; Maslakova et al.
The initial interest in characterizing hunchback (hb) gene products in
protostomes arose from Hb's role as a gap-class segmentation gene in anteroposterior (AP) patterning in dipteran embryos (Lehman and Nusslein-Volhard, 1987; Tautz et al.
So the main question is this: Are the trochophora and dipleurula larvae ancestral to
protostomes and deuterostomes (or perhaps ambulacrarians), respectively, or have these larval types evolved convergently in several clades?
Sexual maturation was shunted to the terminal benthic stage, but the swimming, feeding trochophore and dipleurula were retained as the larval form of
protostomes and deuterostomes, respectively.
18S rRNA suggests that Entoprocta are
protostomes, unrelated to Ectoprocta.
