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PeerJ. 2015 Nov 19;3:e1403. doi: 10.7717/peerj.1403. eCollection 2015.

Phylogenetic analysis of higher-level relationships within Hydroidolina (Cnidaria: Hydrozoa) using mitochondrial genome data and insight into their mitochondrial transcription.

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Department of Invertebrate Zoology, Smithsonian Institution , Washington, DC , USA.
Department of Ecology and Evolutionary Biology, University of Kansas , Lawrence, KS , USA.
Department of Tropical Medicine, Medical Microbiology and Pharmacology, John A. Burns School of Medicine, University of Hawaii at Manoa , Honolulu, HI , USA.
Japan Agency for Marine-Earth Science and Technology (JAMSTEC) , Yokosuka , Japan.
Institute of Marine Science, University of Alaska Fairbanks , Fairbanks, AK , USA.
Department of Invertebrate Zoology, Smithsonian Institution , Washington, DC , USA ; National Systematics Laboratory of NOAA's Fisheries Service, National Museum of Natural History , Washington, DC , USA.


Hydrozoans display the most morphological diversity within the phylum Cnidaria. While recent molecular studies have provided some insights into their evolutionary history, sister group relationships remain mostly unresolved, particularly at mid-taxonomic levels. Specifically, within Hydroidolina, the most speciose hydrozoan subclass, the relationships and sometimes integrity of orders are highly unsettled. Here we obtained the near complete mitochondrial sequence of twenty-six hydroidolinan hydrozoan species from a range of sources (DNA and RNA-seq data, long-range PCR). Our analyses confirm previous inference of the evolution of mtDNA in Hydrozoa while introducing a novel genome organization. Using RNA-seq data, we propose a mechanism for the expression of mitochondrial mRNA in Hydroidolina that can be extrapolated to the other medusozoan taxa. Phylogenetic analyses using the full set of mitochondrial gene sequences provide some insights into the order-level relationships within Hydroidolina, including siphonophores as the first diverging clade, a well-supported clade comprised of Leptothecata-Filifera III-IV, and a second clade comprised of Aplanulata-Capitata s.s.-Filifera I-II. Finally, we describe our relatively inexpensive and accessible multiplexing strategy to sequence long-range PCR amplicons that can be adapted to most high-throughput sequencing platforms.


Aplanulata; Capitata; Filifera; Leptothecata; Low-cost multiplexing library preparation; Mitochondrial gene expression; Phylomitogenomics; Siphonophora

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