The echinoid immune system and the phylogenetic occurrence of immune mechanisms in deuterostomes.
Sea urchin genes expressed in activated coelomocytes are identified by expressed sequence tags: complement homologues and other putative immune response genes suggest immune system homology within the deuterostomes.
Most animal phyla belong to one of two groups of bilaterians: the protostomes or deuterostomes.
The central nervous system in deuterostomes lies on the dorsal side, but on the ventral side in protostomes, such as the lobster.
For example, humans are included in the following nested clades (using the informal names): eukaryotes, animals, deuterostomes
, vertebrates, gnathostomes, tetrapods, amniotes, mammals, eutherians, primates, monkeys, apes, and great apes (see Dawkins, 2004 for more information on the ancestry of humans).
From the basic bilaterian plan, two developmental groups of organisms evolved namely deuterostomes
(echinoderms and chordates) and the protostones (almost everything else).
Glycobiology of sperm-egg interactions in deuterostomes
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).
Could it be that the ancestor of the deuterostomes was a bottom-feeding dweller in the dark?
Of course, eyes are characteristic of the vertebrates in the deuterostome group.
Although PPAR has not been described outside deuterostomes
, RXR is ubiquitous within metazoans.
All species within the phylum Xenacoelomorpha appear to have lost almost all features that define them as deuterostomes
implying a history of extreme evolutionary simplification and loss.