Hidden diversity of Ctenophora revealed by new mitochondrial COI primers
and sequences
Abstract
[Definitive version of this article may be found here] The mitochondrial gene cytochrome-c-oxidase subunit 1 (COI) is useful in
many taxa for phylogenetics, population genetics, metabarcoding, and
rapid species identifications. However, the phylum Ctenophora (comb
jellies) has historically been difficult to study due to divergent
mitochondrial sequences and the corresponding inability to amplify COI
with degenerate and standard COI ‘barcoding’ primers. As a result, there
are very few COI sequences available for ctenophores, despite over 200
described species in the phylum. Here, we designed new primers and
amplified the COI fragment from members of all major groups of
ctenophores, including many undescribed species. Phylogenetic analyses
of the resulting COI sequences revealed high diversity within many
groups that was not evident from more conserved 18S rDNA sequences, in
particular among the Lobata. The COI phylogenetic results also revealed
unexpected community structure within the genus
Bolinopsis,
suggested new species within the genus
Bathocyroe, and supported
the ecological and morphological differences of some species such as
Lampocteis cruentiventer and similar lobates (
Lampocteis
sp. ‘V’ stratified by depth, and ‘A’ differentiated by color). The newly
described primers reported herein provide important tools to enable
researchers to illuminate the diversity of ctenophores worldwide via
quick molecular identifications, improve the ability to analyze
environmental DNA by improving reference libraries and amplifications,
and enable a new breadth of population genetic studies.