16S-LIKE RDNA SEQUENCES FROM DEVELOPAYELLA-ELEGANS, LABYRINTHULOIDES-HALIOTIDIS, AND PROTEROMONAS-LACERTAE CONFIRM THAT THE STRAMENOPILES ARE A PRIMARILY HETEROTROPHIC GROUP

A phylogenetic analysis of the S-16-like ribosomal RNA coding regions from Labyrinthuloides haliotidis, Developayella elegans, Proteromonas lacertae and other organisms corroborates morphological evidence that proteromonads and other eukaryotes with tripartite tubular hairs form a monophyletic group of organisms, the stramenopiles. Within the stram enopiles, the heterotrophic groups (proteromonads, Labyrinthulida, bic osoecids, Developayella and oomycetes) diverge before the radiation of the ''heterokont algae'', the autotrophic stramenopiles. The strameno piles were initially ''protozoan'' but their ecological success is lar gely attributable to the late symbiotic acquisition of chloroplasts. T he stramenopiles and other taxa with chlorophyll a+c containing chloro plasts (cryptomonads, dinoflagellates, and haptophytes) do not share a common autotrophic ancestor. These photosynthetic assemblages acquire d their plastids independently.