The Mitochondrial Genome of Phoronis architecta—Comparisons Demonstrate that Phoronids Are Lophotrochozoan Protostomes

Abstract

The proper reconstruction of the relationships among the animal phyla is central to interpreting patterns of animal evolution from the genomic level to the morphological level. This is true not only of the more speciose phyla but also of smaller groups. We report here the nearly complete DNA sequence of the mitochondrial genome of the phoronid Phoronis architecta, which has a gene arrangement remarkably similar to that of a protostome animal, the chiton Katharina tunicata. Evolutionary analysis of both gene arrangements and inferred amino acid sequences of these taxa, along with those of three brachiopods and other diverse animals, strongly supports the hypothesis that lophophorates are part of the large group that includes mollusks and annelids—i.e., the Lophotrochozoa—and solidly refutes the alternative of their being deuterostomes.