Macroscopic characteristics facilitate identification of common Antarctic glass sponges (Porifera, Hexactinellida, Rossellidae)

Glass sponges (Porifera, Hexactinellida) are conspicuous habitat-forming members of many Antarctic shelf communities. Despite their ecological importance, in-situ species identification remains problematic as it is traditionally based on micro- scopic analysis of spicules. External morphological features, in contrast, have largely been disregarded, so that different species have been mislabeled or lumped together when their identification was based on image material. In this paper, we provide a straight-forward guideline for in-situ identification of the most common rossellid sponges of the Antarctic shelf based on macroscopic characteristics. To determine diagnostic macroscopic characteristics of Anoxycalyx (Scolymastra) joubini and eight Rossella species, we combined examination of trawl-collected specimens, previous species descriptions and in-situ image material from the eastern Weddell Sea. Our study revealed that the smooth-walled species A. joubini, R. nuda and R. vanhoeffeni, previously often mixed up, can be distinguished by the form of their basal spicule tuft, their surface structure and their overall body form. The previously synonymized species R. racovitzae and R. podagrosa can be distinguished by their markedly different habitus. Based on our results, the so-called ‘R. racovitzae budding type’ in fact refers to R. podagrosa which occurs regularly in the eastern Weddell Sea. The species R. villosa, R. levis, R. fibulata and R. antarctica can be distinguished by the appearance of their conules, protruding spicules and overall body form. We conclude that macroscopic characteristics are helpful means for identification of Antarctic rossellid sponge species. This approach enables species-specific quantitative studies of Antarctic glass sponge grounds based on increasingly used non-invasive imaging technology

Self-rehabilitation of acquired brain injury patients including neglect and attention deficit disorder with a tablet game in a clinical setting

We designed and evaluated a whack-a-mole (WAM) style game (see Figure 1) in a clinical randomized controlled trial (RCT) with reminder-assisted but self-initiated use over the period of a month with 43 participants from a post-lesion pool. While game play did not moderate rehabilitative progress indices of standard neuropsychological control tests, it did significantly improve in-game performance when compared to the control group. Its performance indicators and interaction data were highly accurate in predicting neglect and which hand the patients used for input. Patients found playing beneficial to their rehabilitation and attributed gains in the attention training properties of the game. The game showed potential for bedside assessment, insight support, and motivation by providing knowledge about rehabilitative progress

Genetic response to human-induced habitat changes in the marine environment: A century of evolution of European sprat in Landvikvannet, Norway

Habitat changes represent one of the five most pervasive threats to biodiversity. However, anthropogenic activities also have the capacity to create novel niche spaces to which species respond differently. In 1880, one such habitat alterations occurred in Landvikvannet, a freshwater lake on the Norwegian coast of Skagerrak, which became brackish after being artificially connected to the sea. This lake is now home to the European sprat, a pelagic marine fish that managed to develop a self-recruiting population in barely few decades. Landvikvannet sprat proved to be genetically isolated from the three main populations described for this species; that is, Norwegian fjords, Baltic Sea, and the combination of North Sea, Kattegat, and Skagerrak. This distinctness was depicted by an accuracy self-assignment of 89% and a highly significant FST between the lake sprat and each of the remaining samples (average of ≈0.105). The correlation between genetic and environmental variation indicated that salinity could be an important environmental driver of selection (3.3% of the 91 SNPs showed strong associations). Likewise, Isolation by Environment was detected for salinity, although not for temperature, in samples not adhering to an Isolation by Distance pattern. Neighbor-joining tree analysis suggested that the source of the lake sprat is in the Norwegian fjords, rather than in the Baltic Sea despite a similar salinity profile. Strongly drifted allele frequencies and lower genetic diversity in Landvikvannet compared with the Norwegian fjords concur with a founder effect potentially associated with local adaptation to low salinity. Genetic differentiation (FST) between marine and brackish sprat is larger in the comparison Norway-Landvikvannet than in Norway-Baltic, which suggests that the observed divergence was achieved in Landvikvannet in some 65 generations, that is, 132 years, rather than gradually over thousands of years (the age of the Baltic Sea), thus highlighting the pace at which human-driven evolution can happen.publishedVersio

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

Follow-up of the sponge and asteroid populations at the station Larsen A south (PS69/724-1 and PS77/253-1), Antarctic Peninsula, between 2007 and 2011

Over 30% of the Antarctic continental shelf is permanently covered by floating ice shelves, providing aphotic conditions for a depauperate fauna sustained by laterally advected food. In much of the remaining Antarctic shallows (<300 m depth), seasonal sea-ice melting allows a patchy primary production supporting rich megabenthic communities dominated by glass sponges (Porifera, Hexactinellida). The catastrophic collapse of ice shelves due to rapid regional warming along the Antarctic Peninsula in recent decades has exposed over 23,000 km**2 of seafloor to local primary production. The response of the benthos to this unprecedented flux of food is, however, still unknown. In 2007, 12 years after disintegration of the Larsen A ice shelf, a first biological survey interpreted the presence of hexactinellids as remnants of a former under-ice fauna with deep-sea characteristics. Four years later, we revisited the original transect, finding 2- and 3-fold increases in glass sponge biomass and abundance, respectively, after only two favorable growth periods. Our findings, along with other long-term studies, suggest that Antarctic hexactinellids, locked in arrested growth for decades, may undergo boom-and-bust cycles, allowing them to quickly colonize new habitats. The cues triggering growth and reproduction in Antarctic glass sponges remain enigmatic

Rapid Glass Sponge Expansion after Climate-Induced Antarctic Ice Shelf Collapse

SummaryOver 30% of the Antarctic continental shelf is permanently covered by floating ice shelves [1], providing aphotic conditions [2, 3] for a depauperate fauna sustained by laterally advected food [4, 5]. In much of the remaining Antarctic shallows (<300 m depth), seasonal sea-ice melting allows a patchy primary production supporting rich megabenthic communities [6, 7] dominated by glass sponges (Porifera, Hexactinellida) [8–10]. The catastrophic collapse of ice shelves due to rapid regional warming along the Antarctic Peninsula in recent decades [11] has exposed over 23,000 km2 of seafloor to local primary production [12]. The response of the benthos to this unprecedented flux of food [13] is, however, still unknown. In 2007, 12 years after disintegration of the Larsen A ice shelf, a first biological survey interpreted the presence of hexactinellids as remnants of a former under-ice fauna with deep-sea characteristics [14]. Four years later, we revisited the original transect, finding 2- and 3-fold increases in glass sponge biomass and abundance, respectively, after only two favorable growth periods. Our findings, along with other long-term studies [15], suggest that Antarctic hexactinellids, locked in arrested growth for decades [8, 16], may undergo boom-and-bust cycles, allowing them to quickly colonize new habitats. The cues triggering growth and reproduction in Antarctic glass sponges remain enigmatic