Search

The genus Tethya, one of the most iconic groups in the phylum Porifera. includes nearly 100 valid species. Tethya shows a nearly cosmopolitan distribution, and thus this clade could help elucidate global mechanisms of speciation in sponges. Contrasting with many other marine organisms, Tethya peaks in diversity in the temperate region, with only ∼30% of diversity occurring in the tropics. This pattern may however be related to a lack of studies in the tropics, masked by dubious taxonomic identifications. To address this question, we studied new collections from the Western Atlantic (Caribbean and Brazil) and the Northeastern Atlantic, as well as museum material from the Indian Ocean. Combining morphological investigation with molecular phylogenetics and the study of the sponge's microbial communities, we conclude that four constitute new species that we describe here: Tethya martini Riesgo, Giribet, & Santodomingo, sp. nov.; Tethya simoni Santodomingo, Zea, & Riesgo, sp. nov.; Tethya erici Díez-Vives, Santodomingo, Moles, & Riesgo, sp. nov.; Tethya orioni Kenny, Santodomingo & Riesgo, sp. nov. Some species thought to be widespread (e.g., T. aurantium and T. seychellensis), each represent multiple species with unique geographic distributions. A phylogenetic analysis of Tethya (based on COI and 28S rRNA sequence data) recovered five main clades, which were also characterized by distinct prokaryotic communities. This suggests that microbiomes could be used as a guide for taxonomic identification in Tethya. We finally explored the existence of a phylosymbiotic pattern in sponges at different levels of prokaryotic taxonomic resolution (i.e., at phylum, class, and genus-level analysis of prokaryotes). Remarkably, our analysis revealed high levels of coevolution of Tethya and their associated microbial communities, even when microbiomes were analysed at the genus level. Our findings support the use of an integrative approach to better understand the evolutionary history of sponges. [ABSTRACT FROM AUTHOR]

Sponges are interesting animal models for regeneration studies, since even from dissociated cells, they are able to regenerate completely. In particular, explants are model systems that can be applied to many sponge species, since small fragments of sponges can regenerate all elements of the adult, including the oscula and the ability to pump water. The morphological aspects of regeneration in sponges are relatively well known, but the molecular machinery is only now starting to be elucidated for some sponge species. Here, we have used an explant system of the demosponge Halichondria panicea to understand the molecular machinery deployed during regeneration of the aquiferous system. We sequenced the transcriptomes of four replicates of the 5–day explant without an osculum (NOE), four replicates of the 17–18–day explant with a single osculum and pumping activity (PE) and also four replicates of field–collected individuals with regular pumping activity (PA), and performed differential gene expression analysis. We also described the morphology of NOE and PE samples using light and electron microscopy. Our results showed a highly disorganised mesohyl and disarranged aquiferous system in NOE that is coupled with upregulated pathways of ciliogenesis, organisation of the ECM, and cell proliferation and survival. Once the osculum is formed, genes involved in "response to stimulus in other organisms" were upregulated. Interestingly, the main molecular machinery of vasculogenesis described in vertebrates was activated during the regeneration of the aquiferous system. Notably, vasculogenesis markers were upregulated when the tissue was disorganised and about to start forming canals (NOE) and angiogenic stimulators and ECM remodelling machineries were differentially expressed once the aquiferous system was in place (PE and PA). Our results are fundamental to better understanding the molecular mechanisms involved in the formation of the aquiferous system in sponges, and its similarities with the early onset of blood-vessel formation in animal evolution. [ABSTRACT FROM AUTHOR]

Carbonate skeletal remains are altered and disintegrate at yearly to decadal scales in present‐day shallow‐marine environments with intense bioerosion and dissolution. Present‐day brachiopod death assemblages are invariably characterized by poor preservation on continental shelves, and abundant articulated shells of brachiopods with complete brachidia are thus not expected to be preserved if not rapidly buried. However, such preservation is paradoxically observed in shallow‐water Palaeozoic and Mesozoic brachiopod assemblages. Here, we show that a bathyal death assemblage time‐averaged to several millennia (Adriatic Sea) consists of sediment‐filled articulated shells of Gryphus vitreus with complete brachidia. Post‐mortem age distributions indicate that disintegration half‐lives exceed several centuries (c. 500–1700 years). The high frequency of articulated but centuries‐old shells (>50%) and the fitting of taphonomic models to post‐mortem ages indicate that disarticulation half‐life is unusually long (c. 200 years). Rapid sediment filling of shells: (1) inhibited disarticulation, loop fragmentation and colonization by coelobites; and (2) induced precipitation of ferromanganese oxides at redox fronts within shells. Sediment‐filled articulated shells, however, still resided at the sediment–water interface as indicated by encrusters and sponges that infested them after death. Sediment‐filled shells disintegrated through bioerosion and physical wear when residence in the taphonomically active zone exceeded c. 2000 years. We suggest that the articulation paradox is driven by the Mesozoic Marine Revolution (MMR) that escalated predation, bioturbation and organic matter recycling, all intensifying shell disintegration. A scenario with slow disarticulation in bathyal environments may have lead to preservation of articulated shells in shallow‐water assemblages prior to the MMR. [ABSTRACT FROM AUTHOR]

Dissolved silicon (DSi) is biologically processed to produce siliceous skeletons by a variety of organisms including radiolarians, silicoflagellates, choanoflagellates, plants, diatoms and some animals. In the photic ocean, diatoms are dominant consumers over competing other silicifiers. In Antarctica, where DSi is not particularly limiting, diatoms and sponges coexist in high abundances. Interestingly, diatom ingestion by sponges is a regular feeding strategy there. Although it was known that the diatom organic nutrients are readily metabolized by the sponges, what happened to the inorganic diatom silica skeleton remained unexplored. Here, we have conducted a multi-analytical approach to investigate the processing of diatom silica and whether it is reconverted into sponge silica. We have documented widespread diatom consumption by several demosponges, identifying storage vesicles for the diatom-derived silica by electron microscopy and microanalysis. Diatom-consuming sponges showed upregulation of silicatein and silicase genes, which in addition to the δ 30Si values of their silica, supports that the sponges are converting the ingested diatom silica into sponge silica without much further Si fractionation. Our multidisciplinary approach suggests that the reutilization of diatom silica by sponges is a common feature among Antarctic sponges, which should be further investigated in other latitudes and in other silicifiers. [ABSTRACT FROM AUTHOR]

• The first expedition to the depths of the Southern Ocean facing Bremer canyon systems. • First ROV images of these unique deep-sea environments and inhabitants (180 to 3300 m) • Discovery of spectacular 'animal forests' in the Bremer and Hood canyons. • Scleractinian corals found well below the aragonite saturation horizon (>1000 m) • Major fossil coral deposits occur at all three study areas, especially Mount Gabi. Here we present the outcomes of the first deep-sea remotely operated vehicle study of previously unexplored submarine canyon systems along the southwest Australian continental margin. This was conducted around: (1) the Bremer Marine Park; (2) the Mount Gabi seamount and nearby slope-shelf margin at the interface of the Southern and Indian oceans; with new information from (3) the Perth Canyon Marine Park located in the SE Indian Ocean. These canyons differ from many explored around the world in having no connectivity to continental river systems, thus little detrital input, with the Bremer systems and Mount Gabi facing the Southern Ocean which plays a key role in the global ocean circulation and climate systems. Such studies in the vast deep waters around the Australian continent are rare given the lack of local ROV capability available for research, thus little is known about these environments. Using the resources of the Schmidt Ocean Institute, we characterised the submarine topography from high-resolution bathymetric mapping, geology, physical and chemical oceanography, and provide an overview of these environments including the fauna observed and collected. We show that these Southern Ocean-influenced environments incorporate South Indian Central Water, Subantarctic Mode Water, Antarctic Intermediate Water, and Upper and Lower Circumpolar Deep Water, with Antarctic Bottom Water present in deep water just south of the Bremer canyon systems. The richness in megabenthos, especially along the steep, rocky substrates of the canyon heads and walls around the Bremer canyon systems, contrasts to the comparatively depauperate fauna of the more northerly Perth Canyon. Various corals serve as important substrates for a range of other species and often exhibit particular faunal associations. Especially notable are distinct ecological zones including a bryozoan and sponge-dominated (animal) forest on the shelf edge, spectacular coral gardens along canyon margins, and the occurrence of solitary scleractinians well below the aragonite saturation horizon. Subfossil coral deposits were discovered across all three study areas, reflecting periodic waxing and waning of deep-water Scleractinia throughout this southwest region. Extensive pre-modern assemblages at Mount Gabi contrast markedly with the sparse populations of living species and suggest that it might have once been a major coral hotspot, or whether they reflect long-term coral aggregations is yet to be determined. Nevertheless, stark differences in both living and past coral distribution patterns across our study sites point to at least localised fluctuations in Southern Ocean-derived nutrient and/or oxygen supplies to these deep-sea communities. [ABSTRACT FROM AUTHOR]