PHYLOGENETIC-RELATIONSHIPS BETWEEN TOXOPLASMA AND SARCOCYSTIS DEDUCEDFROM A COMPARISON OF 18S RDNA SEQUENCES

The current taxonomy of parasites in the genus Sarcocystis is largely based on morphological characteristics as well as on host specificity and life-cycle structure. Recently, phylogenetic analyses of partial r ibosomal RNA (rRNA) sequences provided support for paraphyly of Sarcoc ystis. We have tested the validity of this hypothesis by sequencing th e complete 18S rRNA genes of Sarcocystis arieticanis, Sarcocystis giga ntea and Sarcocystis tenella and comparing them with gene sequences de rived from other taxa of the phylum Apicomplexa. The results obtained from this study do not reject the hypothesis of monophyly of Sarcocyst is species, although the bootstrap data were inconclusive for some spe cies.