A new Antarctic species of Orchomenella G.O. Sars, 1890 (Amphipoda: Lysianassoidea: Tryphosidae): is phase-contrast micro-tomography a mature technique for digital holotypes?

The purpose of this paper is to describe a new species of Antarctic amphipod of the genus Orchomenella Sars, 1890, Orchomenella rinamontiae sp. nov., and to investigate whether high-resolution images of the surface anatomy obtained ‘in situ’ with synchrotron radiation X-ray phase-contrast micro-tomography (SR-PhC micro-CT) can replace classical approaches to describe a new species. The phylogenetic analyses based on the gene COI support the morphologically based taxonomic assignment. The SR-PhC micro-CT was useful for viewing the three-dimensional reconstructions, with the great advantages that the specimen could be rotated around all axes and that it was possible digitally to remove sections of the image that might have obscured areas of the amphipod on which we were focusing. However, it is not yet a completely reliable technique to describe a new species fully. Classical descriptions using light microscopy and scanning electron microscopy are still necessary. Nevertheless, SR-PhC micro-CT is a promising technique that has the potential to revolutionize the way we study biological samples, accelerating the study of biodiversity.