(1) In contrast to the striking conservation of caspases and bcl - 2 proteins in all animal phyla from Porifera and Cnidaria to mammals, these features of apoptosis are not present in yeast or plants.(2) Between 1859 and 1866, he worked on many ‘invertebrate’ groups, including radiolarians, poriferans and annelids (segmented worms).(3) Thus, poriferan spicules and chancelloriid sclerites do not appear homologous.(4) This pattern is typical of most Porifera , Cnidaria, Bryozoa with coronate larvae, colonial Ascidiacea and many polychaetes.(5) By this usage, the basal metazoans comprise just four phyla (Placozoa, Porifera , Cnidaria, and Ctenophora) and the large clade Bilateria.(6) In that time, the first undoubted fossil annelids, arthropods, brachiopods, echinoderms, molluscs, onychophorans, poriferans , and priapulids show up in rocks all over the world.(7) Of particular interest in this regard are animals in the early diverging non-bilaterian phyla Porifera , Placozoa, Cnidaria, and Ctenophora.(8) For that matter, even the syncytial ‘gut’ departs further from the cnidarian or poriferan system than from the bilaterian archenteron.(9) These allorecognition responses have been recognized for more than a century and have been unequivocally observed in the colonial basal metazoan phyla Porifera and Cnidaria.(10) Results to be discussed below have now extended the occurrence of apoptosis and homologs of caspases and bcl - 2 proteins to the most basal metazoan phyla: Porifera and Cnidaria.
