Complete sequence of the mitochondrial genome of the tapeworm Hymenolepis diminuta: Gene arrangements indicate that platyhelminths are eutrochozoans

Using "long-PCR," we amplified in overlapping fragments the complete mitoch ondrial genome of the tapeworm Hymenolepis diminuta (Platyhelminthes: Cesto da) and determined its 13,900-nt sequence. The gene content is the same as that typically found for animal mitochondrial DNA (mtDNA) except that atp8 appears to be lacking, a condition found previously for several other anima ls. Despite the small size of this mtDNA, there are two large noncoding reg ions, one of which contains 13 repeats of a 31-nt sequence and a potential stem-loop structure of 25 hp with an 11-member loop. Large potential second ary structures were identified also for the noncoding regions of two other cestode mtDNAs. Comparison of the mitochondrial gene arrangement of H. dimi nuta with those previously published supports a phylogenetic position of fl atworms as members of the Eutrochozoa, rather than placing them basal to ei ther a clade of protostomes or a clade of coelomates.