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Haeckel's studies of development in calcareous sponges (1872) led him to develop the 'Gastraea Theory,' which proposes that the ancestral mode of germ layer formation, or gastrulation, was by invagination to produce a functional gut. His observations that gastrulation in the Calcarea occurs by invagination of a ciliated larva upon settlement and metamorphosis were supported by remarkable photomicrographs of the stage by Hammer in 1908. Although no later work found the same stage, these concepts are repeated in texts today. We have re-examined embryogenesis and metamorphosis in Sycon sp. cf. S. raphanus in order to understand when gastrulation occurs. Almost all larvae settle on their ciliated anterior pole and metamorphose into a bilayered juvenile whose interior cells rapidly differentiate into choanocytes and other cells of the young sponge. After a four-year search we have found the transitory stage shown by Hammer in which the anterior cells invaginate into the posterior half of the larva. The hole closes and it is not until some days later that the sponge forms an osculum at its apical pole. To understand whether invagination comprises gastrulation and if the hole can be considered to be a blastopore we have carried out a review of the literature dealing with this brief moment in calcaronean sponge development. Despite the intrigue of this type of metamorphosis, we conclude that gastrulation occurs earlier, during formation of the two cellular regions of the larva, and that metamorphosis involves the reorganization of these already differentiated regions. Considering the pivotal position occupied by the Calcarea as the possible sister-group to all other Metazoa, these results call for a reassessment of germ layer formation and of the relationships of the primary germ layers among basal metazoan phyla.

White mold disease, caused by fungus Sclerotinia sclerotiorum (Lib.) de Bary., is a disease hard to control due to the high amount of sclerotia produced, which guarantees its survival in the soil for years leading to significant yield losses. Alternative techniques to control the pathogen have been researched, including homeopathy. The present work aimed to evaluate the in vitro antifungal effect of homeopathic medicines on S. sclerotiorum mycelial growth. Homeopathic medicines Sulphur, fungal sclerotium Nosode and Calcarea carbonica, in 30CH, 200CH and 1000CH dynamizations were tested. Assays were carried out in a completely randomized design, with four repetitions. Experiments were performed through the addition of homeopathic medicines on the surface of plates containing culture medium, followed by insertion of a disc containing fungus mycelia and incubation. Control treatment received no homeopathic medicine. The mycelial progression was monitored by seven halo diameter measurements during experiment period. All homeopathic medicines tested and their dynamizations were able to inhibit partially the development of the fungus. Calcarea carbonica at the dynamization of 1000 CH showed the best inhibitory effect on S. sclerotiorum, which under its effect produced a mycelial halo 40% smaller than the control treatment.

With the completion of a single unified classification, the Systema Porifera (SP) and subsequent development of an online species database, the World Porifera Database (WPD), we are now equipped to provide a first comprehensive picture of the global biodiversity of the Porifera. An introductory overview of the four classes of the Porifera is followed by a description of the structure of our main source of data for this paper, the WPD. From this we extracted numbers of all 'known' sponges to date: the number of valid Recent sponges is established at 8,553, with the vast majority, 83%, belonging to the class Demospongiae. We also mapped for the first time the species richness of a comprehensive set of marine ecoregions of the world, data also extracted from the WPD. Perhaps not surprisingly, these distributions appear to show a strong bias towards collection and taxonomy efforts. Only when species richness is accumulated into large marine realms does a pattern emerge that is also recognized in many other marine animal groups: high numbers in tropical regions, lesser numbers in the colder parts of the world oceans. Preliminary similarity analysis of a matrix of species and marine ecoregions extracted from the WPD failed to yield a consistent hierarchical pattern of ecoregions into marine provinces. Global sponge diversity information is mostly generated in regional projects and resources: results obtained demonstrate that regional approaches to analytical biogeography are at present more likely to achieve insights into the biogeographic history of sponges than a global perspective, which appears currently too ambitious. We also review information on invasive sponges that might well have some influence on distribution patterns of the future.

Microtubules are the principal cytoskeletal component in cells, integral to various morphogenetic processes in Metazoa, including cell migration, adhesion, and polarity. Their dynamics and functions are modulated by tubulin post-translational modifications (PTMs). While studies on model species have provided insights into microtubule functions, understanding their evolutionary aspects necessitates exploring non-model organisms. Sponges (phylum Porifera) are an early-branching metazoan group with outstanding regenerative capacities. This research presents the first comprehensive analysis of microtubule organization and tubulin PTMs in calcareous sponges. The intact sponge cells show various but typical types of microtubule organization, while detected tubulin PTMs are associated with certain cell types, indicating specific functions in particular cellular contexts. During regeneration, relying on the coordinated movement of epithelial-like cell sheets, microtubule networks in exopinacocytes and choanocytes undergo significant reorganization. These rearranged microtubules potentially stabilize cellular migration direction and facilitate cargo transport, essential for cell contact and polarity establishment. This study enhances our understanding of microtubule functionality and regulation in early-diverging metazoans, contributing to the broader evolutionary context of cytoskeletal dynamics.

Keteleeria davidiana var. calcarea is an endangered plant endemic to China. It is mainly distributed in the karst areas of the Guangxi and Guizhou Provinces. It is characterized by small populations and intermittent distribution. This study aimed to explore the genetic diversity and mating system of wild populations of Keteleeria davidiana var. calcarea in fragmented habitats. To achieve this, we genotyped 46 maternal trees and 214 progenies from four fragmented populations of Keteleeria davidiana var. calcarea using nine pairs of microsatellite primers. The genetic diversity of Keteleeria davidiana var. calcarea (Ho = 0.68, He = 0.63) was lower than that of the species overall but higher than that of other Keteleeria plants. The incidence of unbiased expected heterozygosity (uHe) and allelic richness (Ar) was higher in the maternal generation than in the progeny. This suggests that the genetic diversity of the progeny was lower than that of the maternal generation. Keteleeria davidiana var. calcarea is divided into four populations, but there is significant genetic exchange between the populations according to STRUCTURE and gene flow analyses. The multilocus mating system analysis (MLTR) results indicate that the multilocus outcrossing rate (tm) was 0.902, the single-locus outcrossing rate (ts) was 0.606, the bimaternal inbreeding coefficient (tm-ts) was 0.295, and the coefficient of inbreeding depression(δ) was 0.904. These results suggest a certain degree of selfing and inbreeding in Keteleeria davidiana var. calcarea. To prevent problems associated with inbreeding and conserve the genetic diversity of Keteleeria davidiana var. calcarea, we recommend establishing seed gardens, using artificial pollination, and employing asexual propagation techniques for conservation intervention.

Abstract Calcareous sponges are an often overlooked element of sponge communities. In contrast to most other sponges, calcareous sponges produce calcium carbonate spicules, as opposed to the siliceous spicules of most sponges. Here, we investigated the bacterial communities of 17 sponge species, including type and paratype specimens of recently described calcareous species, sampled off the remote island of Rodrigues, in the Indian Ocean. The main axis of variation in a PCO analysis of all samples separated noncalcareous sponge species, including Axinyssa aplysinoides, Cinachyrella aff. australiensis, Petrosia seychellensis, Ircinia aff. variabilis, Spongia ceylonensis, Plakinastrella aff. clipptertonensis, Agelas aff. ceylonica, Agelas aff. mauritiana, and Hyrtios erectus from calcareous sponges, the noncalcareous Biemna tubulata, sediment, and seawater. Overall, the bacterial communities of calcareous sponges revealed unique prokaryotic profiles with low abundances of several bacterial phyla, and relatively high abundances of other taxa, for example, the phyla Fibrobacterota, Proteobacteria, and the SAR324 clade, the class Alphaproteobacteria, and orders Cytophagales and Cyanobacteriales, although there was considerable variation among species. Calcareous sponges also had a high dominance of unknown bacterial operational taxonomic units (OTUs). Considering the unique nature of these communities, further studies are needed to better understand the environmental and ecological drivers of calcareous sponge-associated bacterial communities and their relevance as potential sources of novel microbes of biotechnological interest. Sponge species, including calcareous and non-calcareous species, were sampled from the remote island of Rodrigues revealing unique prokaryotic profiles and a high dominance of unknown operational taxonomic units.

Background Approximately 80% of all described extant sponge species belong to the class Demospongiae. Yet, despite their diversity and importance, accurate divergence times are still unknown for most demosponge clades. The estimation of demosponge divergence time is key to answering fundamental questions on the origin of Demospongiae, their diversification and historical biogeography. Molecular sequence data alone is not informative on an absolute time scale, and therefore needs to be “calibrated” with additional data such as fossils. Here, we calibrate the molecular data with the fossilized birth-death model, which compared to strict node dating, allows for the inclusion of young and old fossils in the analysis of divergence time. We use desma-bearing sponges, a diverse group of demosponges that form rigid skeletons and have a rich and continuous fossil record dating back to the Cambrian (~500 Ma), to date the demosponge radiation and constrain the timing of key evolutionary events, like the transition from marine to freshwater habitats. To infer a dated phylogeny of Demospongiae we assembled the mitochondrial genomes of six desma-bearing demosponges from reduced-representation genomic libraries. The total dataset included 33 complete demosponge mitochondrial genomes and 30 fossils. Results Our study supports a Neoproterozoic origin of Demospongiae. Novel age estimates for the split of freshwater and marine sponges dating back to the Carboniferous and the previously assumed recent (~18 Ma) diversification of freshwater sponges is supported. Moreover, we provide detailed age estimates for a possible diversification of Tetractinellidae (~315 Ma), the Astrophorina (~240 Ma), the Spirophorina (~120 Ma) and the family Corallistidae (~188 Ma) all of which are considered as key groups for dating the Demospongiae due to their extraordinary rich and continuous fossil history. Conclusion This study provides novel insights into the evolution of Demospongiae. Observed discrepancies of our dated phylogeny with their putative first fossil appearance dates are discussed for selected sponge groups. For instance, a Carboniferous origin of the order Tetractinellida seems to be too late, compared to their first appearance in the fossil record in the Middle Cambrian. This would imply that Paleozoic spicule forms are not homologous to post-Paleozoic forms.

Sponges play a key role in Antarctic marine benthic community structure and dynamics and are often a dominant component of many Southern Ocean benthic communities. Understanding the drivers of sponge distribution in Antarctica enables us to understand many of general benthic biodiversity patterns in the region. The sponges of the Antarctic and neighbouring oceanographic regions were assessed for species richness and biogeographic patterns using over 8,800 distribution records. Species-rich regions include the Antarctic Peninsula, South Shetland Islands, South Georgia, Eastern Weddell Sea, Kerguelen Plateau, Falkland Islands and north New Zealand. Sampling intensity varied greatly within the study area, with sampling hotspots found at the Antarctic Peninsula, South Georgia, north New Zealand and Tierra del Fuego, with limited sampling in the Bellingshausen and Amundsen seas in the Southern Ocean. In contrast to previous studies we found that eurybathy and circumpolar distributions are important but not dominant characteristics in Antarctic sponges. Overall Antarctic sponge species endemism is ∼43%, with a higher level for the class Hexactinellida (68%). Endemism levels are lower than previous estimates, but still indicate the importance of the Polar Front in isolating the Southern Ocean fauna. Nineteen distinct sponge distribution patterns were found, ranging from regional endemics to cosmopolitan species. A single, distinct Antarctic demosponge fauna is found to encompass all areas within the Polar Front, and the sub-Antarctic regions of the Kerguelen Plateau and Macquarie Island. Biogeographical analyses indicate stronger faunal links between Antarctica and South America, with little evidence of links between Antarctica and South Africa, Southern Australia or New Zealand. We conclude that the biogeographic and species distribution patterns observed are largely driven by the Antarctic Circumpolar Current and the timing of past continent connectivity.

Sponges are known to possess remarkable reconstitutive and regenerative abilities ranging from common wounding or body part regeneration to more impressive re-building of a functional body from dissociated cells. Among the four sponge classes, Homoscleromorpha is notably the only sponge group to possess morphologically distinct basement membrane and specialized cell-junctions, and is therefore considered to possess true epithelia. The consequence of this peculiar organization is the predominance of epithelial morphogenesis during ontogenesis of these sponges. In this work we reveal the underlying cellular mechanisms used during morphogenesis accompanying ectosome regeneration in the homoscleromorph sponge model: Oscarella lobularis. We identified three main sources of novel exopinacoderm during the processes of its regeneration and the restoration of functional peripheral parts of the aquiferous system in O. lobularis: (1) intact exopinacoderm surrounding the wound surface, (2) the endopinacoderm from peripheral exhalant and inhalant canals, and (3) the intact choanoderm found on the wound surface. The basic morphogenetic processes during regeneration are the spreading and fusion of epithelial sheets that merge into one continuous epithelium. Transdifferentiation of choanocytes into exopinacocytes is also present. Epithelial-mesenchymal transition is absent during regeneration. Moreover, we cannot reveal any other morphologically distinct pluripotent cells. In Oscarella, neither blastema formation nor local dedifferentiation and proliferation have been detected, which is probably due to the high morphogenetic plasticity of the tissue. Regeneration in O. lobularis goes through cell transdifferentiation and through the processes, when lost body parts are replaced by the remodeling of the remaining tissue. Morphogenesis during ectosome regeneration in O. lobularis is correlated with its true epithelial organization. Knowledge of the morphological basis of morphogenesis during Oscarella regeneration could have important implications for our understanding of the diversity and evolution of regeneration mechanisms in metazoans, and is a strong basis for future investigations with molecular-biological approaches.

Sponges-associated microorganisms play important roles in their health and ecology; consequently, they may be crucial in the successful adaptation of exotic species to novel environments. However, few studies have focused on the microbial diversity of exotic sponges, especially those with calcium carbonate spicules (class Calcarea). Therefore, this is the first in situ characterization of the microbiota of the exotic calcareous sponges Sycettusa hastifera and Paraleucilla magna . Our results suggest that S . hastifera has a more stable microbiota than P . magna , as there were no differences in its beta diversity among sampling sites. Conversely, P . magna showed significant differences in its microbial communities, perhaps related to its adhesion to artificial substrate and/or shellfish mariculture activities. Each sponge species presented a single dominant proteobacterial OTU potentially active in the nitrogen cycle, which could help sponge detoxification, especially in polluted areas where exotic species usually establish. Our results show the importance of assessing the microbial diversity to unveil host-microorganism relationships and suggest that these associated nitrogen-cycling microorganisms could favor the success of exotic sponges in new environments.