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.
The central nervous system in deuterostomes lies on the dorsal side, but on the ventral side in
protostomes, such as the lobster.
These differences raise the question of what the ancestral clock was like before the divergence of
protostomes and deuterostomes.
In N-linked saccharide chains of species belonging to
protostomes (nematode, squid, and limpets, etc.), galactose residues at the non-reducing ends are known to bind to a fucose residue attaching to the innermost GlcNAc residue via [beta]1-4 linkage.
Bilateral symmetry is found in 3 major clades of animals: the Deuterostomes (which includes vertebrates) and two clades of
Protostomes, the Ecdysozoa (which includes arthropods and nematodes) and the Lophotrochozoa (which includes molluscs and annelids).
While it has been variously suggested that deuterostomes (Nursall, 1962),
protostomes (Inglis, 1985), and cnidarians (Hanson, 1977) independently evolved multicellularity, the group most commonly considered to have been derived from a separate protist lineage is the sponges, phylum Porifera (as evidenced by Barnes, 1980, p.
Eggs of these
protostomes have certain features that make them more similar to mammalian oocytes than to echinoderm or coelenterate eggs.
(198) Further investigation on the diversity of flagella and cilia in the future using well-known species or those newly found, such as loss of motile cilia in plants or a certain group of
protostomes and compound cilia or macrocilia in metazoa, should shed new light on the biology of dynein and tubulin.
The majority of these articles cover deuterostome animals (e.g., chordates and echinoderms) rather than
protostomes (e.g., arthropods and molluscs), and most recent reviews of such topics have concentrated on the vast literature that has been compiled for mammals (e.g., Evans and Gadella, 2011; Kang and Han.
The formation of the germ cells at the poste-riormost region of embryos is also observed in
protostomes, suggesting that the manner of germ cell formation is conserved among
protostomes and deuterostomes.
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., 2004).
