A vascularized model of the human liver mimics regenerative responses.

Liver regeneration is a well-orchestrated process that is typically studied in animal models. Although previous animal studies have offered many insights into liver regeneration, human biology is less well understood. To this end, we developed a three-dimensional (3D) platform called structurally vascularized hepatic ensembles for analyzing regeneration (SHEAR) to model multiple aspects of human liver regeneration. SHEAR enables control over hemodynamic alterations to mimic those that occur during liver injury and regeneration and supports the administration of biochemical inputs such as cytokines and paracrine interactions with endothelial cells. We found that exposing the endothelium-lined channel to fluid flow led to increased secretion of regeneration-associated factors. Stimulation with relevant cytokines not only amplified the secretory response, but also induced cell-cycle entry of primary human hepatocytes (PHHs) embedded within the device. Further, we identified endothelial-derived mediators that are sufficient to initiate proliferation of PHHs in this context. Collectively, the data presented here underscore the importance of multicellular models that can recapitulate high-level tissue functions and demonstrate that the SHEAR device can be used to discover and validate conditions that promote human liver regeneration.

Sediment DNA metabarcoding and morphology provide complementary insight into macrofauna and meiobenthos response to environmental gradients in an Arctic glacial fjord.

Arctic fjords ecosystems are highly dynamic, with organisms exposed to various natural stressors along with productivity clines driven by advection of water masses from shelves. The benthic response to these environmental clines has been extensively studied using traditional, morphology-based approaches mostly focusing on macroinvertebrates. In this study we analyse the effects of glacially mediated disturbance on the biodiversity of benthic macrofauna and meiobenthos (meiofauna and Foraminifera) in a Svalbard fjord by comparing morphology and eDNA metabarcoding. Three genetic markers targeting metazoans (COI), meiofauna (18S V1V2) and Foraminifera (18S 37f) were analyzed. Univariate measures of alpha diversity and multivariate compositional dissimilarities were calculated and tested for similarities in response to environmental gradients using correlation analysis. Our study showed different taxonomic composition of morphological and molecular datasets for both macrofauna and meiobenthos. Some taxonomic groups while abundant in metabarcoding data were almost absent in morphology-based inventory and vice versa. In general, species richness and diversity measures in macrofauna morphological data were higher than in metabarcoding, and similar for the meiofauna. Both methodological approaches showed different patterns of response to the glacially mediated disturbance for the macrofauna and the meiobenthos. Macrofauna showed an evident distinction in taxonomic composition and a dramatic cline in alpha diversity indices between the outer and inner parts of fjord, while the meiobenthos showed a gradual change and more subtle responses to environmental changes along the fjord axis. The two methods can be seen as complementing rather than replacing each other. Morphological approach provides more accurate inventory of larger size species and more reliable quantitative data, while metabarcoding allows identification of inconspicuous taxa that are overlooked in morphology-based studies. As different taxa may show different sensitivities to environmental changes, both methods shall be used to monitor marine biodiversity in Arctic ecosystems and its response to dramatically changing environmental conditions.

Nematode responses to an Arctic sea-ice regime: morphometric characteristics and biomass size spectra.

Body size is one of the most important traits of organisms that affects their behavioral life histories, physiologies, and energy requirements. For sediment-dwelling organisms, such as free-living nematodes, body size is a direct adaptation for living in sediments with a particular particle size, but other environmental factors, e.g., water depth and food availability, directly or indirectly shape nematode morphology. Nevertheless, our knowledge of meiofaunal organisms sizes still lags far behind that of other aquatic fauna, particularly for high-latitude fauna. Therefore, to gain insight into the nematode community size structure, we investigated eight stations located in the seasonal sea-ice zone north of Svalbard (Yermak Plateau, Nansen Basin, and Northern Svalbard shelf) during Arctic spring. Sample locations covered a wide depth gradient, different sea-ice concentrations and subsequent bloom stages. Our study provides previously unavailable data on nematode morphometry for this Arctic region during ecologically important spring to summer transition times. We analyzed nematode biomass, body shape and morphometric attributes, along with respective feeding types and life stage information. Our results show that differences in nematode densities, biomass and allometric attributes most likely reflect differences in the flux of organic material to the seafloor and in the biogeochemical properties of the sediments. Nematode assemblages appeared to respond to spatial gradients in ice cover duration and therefore pelagic productivity from the northern Svalbard shelf to the Yermak Plateau as evidenced by decreasing density, biomass and body size. Considering the entire community, as well as different life stages, average individual body weight decreased northward. Biomass dominance in the lower weight classes and the significantly lower abundance of long and thick morphotype nematodes observed on the Yermak Plateau than in the two other regions were striking. This was in contrast with the assemblage observed on the shelf, where prevailing environmental conditions influenced the presence of other morphotypes - markedly longer and wider organisms. Ongoing changes in sea-ice cover and primary production in the Arctic may significantly affect nematode functioning, as they are expected to have pronounced impacts on nematode morphological characteristics. In this regard, the size-based approach becomes a useful tool for detecting changes in the community and has important implications for predicting the direction of change with regard to benthic productivity.

New mud dragons from Svalbard: three new species of Cristaphyes and the first Arctic species of Pycnophyes (Kinorhyncha: Allomalorhagida: Pycnophyidae).

BACKGROUND: Kinorhynchs are marine, microscopic invertebrates inhabiting the seafloors. Their segmented trunk equipped with spines and processes has inspired scientists to give them the common name "mud dragons." Even though kinorhynchs have been known since the 19th century, less than 300 species are known to science, and it is still considered a largely understudied animal group-in particular in the Arctic, from which only 23 species are known so far. METHODS: Samples were collected at eight stations around Svalbard and in the fjords of Spitsbergen. Meiofauna was extracted from the sediment cores with LUDOX centrifugation method, and kinorhynchs were picked up and mounted for light- and scanning electron microscopy. RESULTS: Four new species of the kinorhynch family Pycnophyidae are described from Svalbard: Cristaphyes dordaidelosensis sp. nov., C. glaurung sp. nov., C. scatha sp. nov., and Pycnophyes ancalagon sp. nov. The new species are generally recognized by their distribution of setae along the trunk segments. DISCUSSION: After the discovery of the new species, Pycnophyidae becomes with 14 species the most diverse kinorhynch genus in the Arctic, closely followed by Echinoderidae with 13 species. So far, these are the only kinorhynch families with an Arctic distribution.

Ecostructuring of marine nematode communities by submarine groundwater discharge.

Inputs of submarine groundwater discharge (SGD) to the coastal ocean may alter local and regional-scale biology. Here, we report on nematode assemblages along the north shore of Long Island, NY. We test if nematode communities differed between sites impacted by mixed fresh-saline SGD and where SGD is exclusively saline. Diversity of nematodes was low at sites impacted by fresh SGD and communities were dominated by a few opportunistic genera. Moreover, a set of typical freshwater nematode genera restricted to impacted sites was observed. Their presence in the marine coastal zone is exceptional and underlines the structuring role that fresh SGD plays in the local ecosystem. Saline SGD structured nematode assemblages differently compared to sites impacted by fresh SGD. The number of nematode genera was markedly higher at saline SGD sites, with a different community structure. This study highlights the importance to which inputs of fresh SGD may have on local ecosystem diversity in marine coastal environments.

Echinoderes pterus sp. n. showing a geographically and bathymetrically wide distribution pattern on seamounts and on the deep-sea floor in the Arctic Ocean, Atlantic Ocean, and the Mediterranean Sea (Kinorhyncha, Cyclorhagida).

Kinorhynchs rarely show a wide distribution pattern, due to their putatively low dispersal capabilities and/or limited sampling efforts. In this study, a new kinorhynch species is described, Echinoderes pterussp. n., which shows a geographically and bathymetrically wide distribution, occurring on the Karasik Seamount and off the Svalbard Islands (Arctic Ocean), on the Sedlo Seamount (northeast Atlantic Ocean), and on the deep-sea floor off Crete and on the Anaximenes Seamount (Mediterranean Sea), at a depth range of 675-4,403 m. The new species is characterized by a combination of middorsal acicular spines on segments 4-8, laterodorsal tubes on segment 10, lateroventral tubes on segment 5, lateroventral acicular spines on segments 6-9, tufts of long hairs rising from slits in a laterodorsal position on segment 9, truncated tergal extensions on segment 11, and the absence of any type-2 gland cell outlet. The specimens belonging to the populations from the Arctic Ocean, the Sedlo Seamount, and the Mediterranean Sea show morphological variation in the thickness and length of the spines as well as in the presence/absence of ventromedial sensory spots on segment 7. The different populations are regarded as belonging to a single species because of their overlapping variable characters.

Checklist of Gastrotricha of the Polish Baltic Sea with the first reports of Heterolepidoderma joermungandri Kånneby, 2011, and Turbanella hyalina Schultze, 1853.

Gastrotricha is a cosmopolitan phylum of aquatic and semi-terrestrial invertebrates comprising more than 800 described species. Up to now, only five taxonomic and faunistic papers have been published on the gastrotrichs of the Polish Baltic Sea and 27 taxa have been found (including three freshwater, which were found in estuaries). This article presents a complete list of brackish and estuarine Gastrotricha from the Polish Baltic Sea accompanied by localities and the first observations of gastrotrich species inhabiting the underwater macrophytes. Although the group has been studied for more than 150 years, the gastrotrich community of marine macrophytes has not been studied in any great detail. Here we provide data on gastrotrich communities living on macrophytes and also in sandy sediments. In total, nine species were found (seven from sandy sediments, two species from macrophytes). Seven of the species belong to Chaetonotida: Halichaetonotus balticus Kisielewski, 1975, H. lamellatus Kisielewski, 1975, H. schromi Kisielewski, 1975, Heterolepidoderma joermungandri Kånneby, 2011, Lepidodermella squamata (Dujardin, 1841), Xenotrichula intermedia Remane, 1934, and X. velox Remane, 1927(c). Two of species belong to Macrodasyida: Turbanella cornuta Remane, 1925, and T. hyalina Schultze, 1853. H. joermungandri and T. hyalina are new for Polish fauna. Both species correspond with the original descriptions but differ by some morphometric characters. Taxonomic, morphometric, and biogeographic remarks are provided for the new records together with differential interference contrast (DIC) microphotographs.