focused on the mitochondrial cytochrome c oxidase
subunit I (COI) gene because it appears to be
among the most conservative protein-coding genes
in the mitochondrial genome of animalswhich was preferable for the evolutionary time depths likely to be found in our studies.
We quickly became aware of the broad utility of
these COI primers for broader systematic studies
of metazoan invertebrates, including acoelomates,
pseudocoelomates, and coelomate protostomes and
deuterostomes.