Extraordinary eyes reveal hidden diversity within the holopelagic genus Paraphronima (Amphipoda: Hyperiidea)

November 11, 2021

Vanessa I. Stenvers (1,2,3), Brett C. Gonzalez (1), Freya E. Goetz (1), Jan M. Hemmi (4), Anna-Lee Jessop (4), Chan Lin (1), Henk-Jan T. Hoving (2), Karen J. Osborn (1,5)
Deep Sea Research Part I: Oceanographic Research Papers, 177, November 2021. DOI: 10.1016/j.dsr.2021.103610


Systematics; DNA taxonomy; Micro-computed tomography (μCT); Cryptic species; Open ocean; Midwater


Holopelagic animals were long assumed to have widespread geographic distributions due to the failure to recognize hydrographic species' barriers in the open ocean. As molecular genetic tools are more commonly used to study the ocean's inhabitants, diversity is found to be substantially higher than when inferred from morphological taxonomies alone. Here, we investigate the morphological and genetic diversity of hyperiid amphipods within the genus Paraphronima, currently comprising two supposedly cosmopolitan species. By combining phylogenetic analyses and four species delimitation methods (GMYC, mPTP, bPTP, ABGD), we reveal substantial species-level genetic variation. Instead of two species inhabiting multiple ocean basins, the biogeography of Paraphronima species appears to be limited to more regional scales. Moreover, there is morphological evidence to corroborate the observed genetic diversity. By using an integrative morpho-molecular approach, a third species from the Gulf of California, Paraphronima robisoni sp. nov., is described. Interestingly, the morphological characters that best distinguish the species within the genus are characters of the compound eyes, which have rarely been used for taxonomy despite being the most obvious and varied features of hyperiids. Our results warrant further investigation of presumably cosmopolitan holopelagic amphipods, while we recommend the inclusion of eye morphology in future taxonomic studies.

How Our Software Was Used

Dragonfly was used to analyze micro-CT data.

Author Affiliation

(1) Department of Invertebrate Zoology, National Museum of Natural History, Smithsonian Institution, Washington, DC, 20013, USA.
(2) GEOMAR Helmholtz Centre for Ocean Research Kiel, Düsternbrooker Weg 20, 24105, Kiel, Germany.
(3) Faculty of Science and Engineering, University of Groningen, Nijenborgh 4, 9747, AG Groningen, the Netherlands.
(4) School of Biological Sciences & UWA Oceans Institute, The University of Western Australia, Perth, WA, 6009, Australia.
(5)Monterey Bay Aquarium Research Institute, 7700 Sandholdt Road, Moss Landing, CA, 95039-9644, USA.