Reference images for identification of common Antarctic glass sponges (Porifera: Hexactinellida: Rossellidae) based on macroscopic characteristics

Glass sponges (Porifera: Hexactinellida) are important structuring elements in many Antarctic shelf communities. Despite many years of research on their ecology, species identification in the common genus Rossella and distinction against the well-studied species Anoxycalyx (Scolymastra) joubini remain problematic. The two main problems are: (1) the unresolved taxonomy of the genus Rossella which is in dire need of revision, and (2) the high morphological variability of some species. Some of the confusion is due to the fact that early species descriptions are partly based on very small individuals or just fragments and are often not comprehensive or clear enough. They usually focus on the spicules and include little information on the general external morphology of the species. However, with the increasing use of non-invasive techniques, such as Remotely Operated Vehicles (ROVs) and other camera systems, researchers have to rely on macroscopic features to identify species, and a working concept to this effect is required right away. We found that it is possible to reliably identify some common Antarctic sponge species based on macroscopic characteristics. This Data Collection contains a wide range of images of the currently well-established species of Antarctic Rossellidae, showing the macroscopic features typical for each species and morphological differences between similar species according to our current understanding. It includes photographs of freshly collected and dried specimens, as well as in situ images recorded by ROVs. We provide a large number of images to showcase the morphological variability and show with detailed images that the same macroscopic characteristics can be observed in collected specimens and in situ. For identification and description of Antarctic glass sponges, it is important to take into consideration not only the spicules and molecular data, but the outer morphology, as well. Therefore, we encourage everybody to use the images provided in this Data Collection as reference material.