Hexactinellid Research Articles

Tensile and fracture behavior of silica fibers from the Venus flower basket (Euplectella aspergillum)

The extraordinary mechanical properties shown by many biological materials stem from their unique hierarchical structures. The spicules of the deep-sea glass sponge, Euplectella aspergillum, show layered architecture and are known to improve toughness in various loading conditions. In the present work, we conducted a systematic study on the tensile and fracture behavior of E. aspergillum’s spicules. Tensile tests were performed on three different gage lengths of spicules that compose anchoring structures of E. aspergillum. The cross-sectional area of each spicule was accurately measured using an x-ray microscope. The effect of gage length and varying cross-sectional area on the tensile behavior of spicules is discussed in detail. The interplay between two failure initiation sites, namely, weakest-link flaws and minimum cross-sectional area locations was observed. Weibull statistics were used to quantify the variability in the strengths of spicules as a function of their gage length. The Weibull modulus was observed to decrease with the increase in gage length. The possibility of a bimodal flaw population for a higher gage length of spicules due to the interplay between failure initiation sites is also discussed. The fractography study was utilized to understand the failure and toughening mechanisms of spicules in tensile loading. The fracture toughness of the central core was quantified from fracture surfaces using a linear elastic fracture mechanics model. The present study shows that the failure of spicules initiates in the outer layers and proceeds progressively to the center. The layers surrounding the central core of the spicule resist the crack propagation and increase its toughness.

Population structure of Asconema setubalense Kent, 1870 at Concepción Seamount, Canary Islands (Spain). Methodological approach using non-invasive techniques

The hexactinellid sponge Asconema setubalense Kent, 1870is a large bathyal species of the North Atlantic Ocean with a funnel-like body and very large osculum. Populations of A. setubalense have a three-dimensional structure and increase the complexity and biodiversity in their habitat, and are therefore considered to be a habitat-forming species. Nevertheless, at present the information on the extension, biomass, density, population structure, and ecology of this species is scarce, and it could be susceptible to the longline fishing practices that take place in the Canary Islands.The main objectives of this study are to define a functional and accurate methodology to measure specimens of A. setubalense by comparing differences in users, techniques, and morphometric measurements; to describe the height-size relationship; to present the population size structure of the species, and to establish a relationship between the size of A. setubalense and the environmental variables that can be found at the “Banco de La Concepción” seamount (BC). The obtained results suggest that surface area is the most reliable measurement to define the size of this species, whilst also showing a clear correlation with the height of the species. The selected methodology has made it possible to measure the surface area of 1035 specimens and thus obtain the size structure of the population of A. setubalense in BC. The GAM model that was used to analyse the relationship between the size of A. setubalense and the geomorphologic variables of BC, shows areas where there is a high probability of finding large specimens of the species. The results of this study greatly enhance the knowledge of this species and its habitat, and should be considered in future conservation directives, or in the development of indicators to show the good environmental state of habitats. Additionally, the study improves analysis methodology that, with the appropriate morphometric measurements, can favour the development of future studies of this species, and indeed others with a similar morphology or growth pattern.

Anisotropic compression behaviors of bio-inspired modified body-centered cubic lattices validated by additive manufacturing

Bio-inspired lattices have been proved to possess better energy absorption capacity than conventional structures. Here, the two-dimensional deep-sea glass sponge structure is extended to three-dimensional and further topologically optimized to design a novel lattice called modified body-centered cubic (MBCC) lattice. The quasi-static compression behavior of different lattices was investigated via extensive finite element (FE) simulations validated by the experimental tests. The results indicated that the proposed MBCC design can further increase the energy absorption capacity compared with the previous bio-inspired and the conventional body-centered cubic designs. Impressively, the new lattice made of steel exhibits specific energy absorption close to that of foams made of titanium alloy. In addition, the influences of the deviation coefficient and the loading direction on the compressive behaviors of MBCC lattice are investigated parametrically. The proposed lattice structures present a new deformation mode and peculiar anisotropy regarding to the specific strength and the oscillation in the stress-strain curves.

Hadal Biodiversity, Habitats and Potential Chemosynthesis in the Java Trench, Eastern Indian Ocean

The Java Trench is the only subduction trench in the Indian Ocean that extends to the hadal zone (> 6,000 m water depth), and except for sevenbenthic trawls acquired around the 1950s, there has been little to no sampling at hadal depths undertaken since. In 2019, we undertook a 5-day expedition comprising a scientific dive using a full ocean depth-rated submersible, the DSV Limiting Factor, seven hadal-lander deployments, and high-resolution bathymetric survey. The submersible performed a video transect from the deepest point of the trench, up a 150 m high near-vertical escarpment located on the forearc, and then across a plateau at a depth of ∼7,050 m to make in situ observations of the habitat heterogeneity and biodiversity inhabiting these hadal depths. We found the Java Trench hadal community to be diverse and represented by 10 phyla, 21 classes, 34 orders and 55 families, with many new records and extensions in either depth or geographic range, including a rare encounter of a hadal ascidian. The submersible transect revealed six habitats spanning the terrain. The deepest trench axis comprised fine-grained sediments dominated by holothurians, whereas evidence of active rock slope failure and associated talus deposits were prevalent in near-vertical and vertical sections of the escarpment. Sediment pockets and sediment pouring down the steep wall in “chutes” were commonly observed. The slope terrain was dominated by two species in the order Actiniaria and an asteroid, as well as 36 instances of orange, yellow, and white bacterial mats, likely exploiting discontinuities in the exposed bedrock, that may indicate a prevalence of chemosynthetic input into this hadal ecosystem. Near the top of the escarpment was an overhang populated by > 100 hexactinellid (glass) sponges. The substrate of the plateau returned to fine-grained sediment, but with a decreased density and diversity of epifauna relative to the trench floor. By providing the first visual insights of the hadal habitats and fauna of the Java Trench, this study highlights how the habitat heterogeneity influences patchy species distributions, and the great benefit of using a hadal-rated exploratory vehicle to comprehensively assess the biodiversity of hadal ecosystems.

First hexactinellid spicules from the Late Cambrian olitofish of the Los Sombreros Formation, Tontal Range, San Juan Precordillera, Argentina

A moderately diverse fauna of hexactinellid sponges is described from one Late Cambrian olitofish of the Los Sombreros Formation from Tres Saltos Gulch in the Tontal Range, Western Precordillera, San Juan Province. Argentina. Protospongia sp., Diagoniella? Sp., Kiwetinokia, anchoring spicules, prodiaenes, diagonally arranged spicules and root tuft are present. The preservation degree of the spicules and the patterns allow us to presume that after their death, they were transported not very far from the original sponges oases. The Cambrian oolitic grainstone limestone with spicules conform an olitofish which was transported and resedimented during the Ordovician by gravity flows within a pelitic matrix of the terrigenous-carbonate talus of the Los Sombreros Formation.

Extraordinarily early Venus' flower basket sponges (Hexactinellida, Euplectellidae) from the uppermost Ordovician Anji Biota, China

AbstractThe deep‐sea hexactinellid sponge Euplectella is an iconic living genus with no known fossil record. The family Euplectellidae (which includes a subset of genera that share the common name ‘Venus' flower basket’) has a very sparse record from the Middle Cretaceous onwards, and an estimated crown‐group origin at around 300 Ma based on molecular clocks. New material of Venus' flower baskets from the latest Ordovician Anji Biota of China (444 Ma) dramatically extends the known and predicted range of the group, with implications for the diversification of the class Hexactinellida and the timing of development of deep‐sea ecosystems. The new material is described as Anjiplectella davidipharus gen. et sp. nov., with an additional taxon remaining in open nomenclature but demonstrating diversification within the group by this time.

Arrested in Glass: Actin within Sophisticated Architectures of Biosilica in Sponges.

Actin is a fundamental member of an ancient superfamily of structural intracellular proteins and plays a crucial role in cytoskeleton dynamics, ciliogenesis, phagocytosis, and force generation in both prokaryotes and eukaryotes. It is shown that actin has another function in metazoans: patterning biosilica deposition, a role that has spanned over 500 million years. Species of glass sponges (Hexactinellida) and demosponges (Demospongiae), representatives of the first metazoans, with a broad diversity of skeletal structures with hierarchical architecture unchanged since the late Precambrian, are studied. By etching their skeletons, organic templates dominated by individual F‐actin filaments, including branched fibers and the longest, thickest actin fiber bundles ever reported, are isolated. It is proposed that these actin‐rich filaments are not the primary site of biosilicification, but this highly sophisticated and multi‐scale form of biomineralization in metazoans is ptterned.

A probable hyalonematid sponge (Hexactinellida: Amphidiscophora) from the Middle Ordovician of the Builth Inlier, Wales

Modern hexactinellid sponges are diverse, but almost exclusively deep-marine organisms with a very intermittent fossil record. Aside from the fused skeletons of hexactinosan lineages (which are also exceptionally rare in Palaeozoic sediments), identifying other families is challenging due to the microscopic nature of many diagnostic characters, and the need for exceptional preservation in a deep-water palaeoenvironment. Among the more distinctive living families is the Hyalonematidae, which have several preservable diagnostic features. A new sponge (Nectocollare zakdouli n. gen. n. sp.) from the Middle Ordovician Castle Bank fauna of Wales, UK, shows several of these characters, including pinular pentactine dermalia, unbundled choanosomal diactins, and a reticulate marginal rim at the apex. No root tuft is preserved, but these are often detached from fossil sponges. Although there remains some uncertainty over the assignment to Hyalonematidae, this sponge represents the only probable example from the Palaeozoic. Even in the absence of diagnostic microscleres, it likely represents a derived, crown-group hexactinellid, and further confirms the diversification of the class during the earliest Palaeozoic.

Super durable graphene aerogel inspired by deep-sea glass sponge skeleton

Herein, a facile hydrothermal self-assembling strategy is employed to prepare a reduced graphene oxide (rGO) aerogel with a multi-scale hierarchical cellular structure inspired by deep-sea glass sponge. This hierarchical cellular structure of the rGO aerogel, obtained by changing the carbon wall to cellular structure, can be broken down into six levels from the nano- to the macro-scale. Remarkably, the rGO aerogel, with multi-step reductions, shows significant flexibility and toughness under extra-high compressions: 99.9% of the original height is remained after 20 000 compression cycles at a high strain of 90%, whereas 79.8% of height is still preserved after 10 000 compression cycles at an extreme strain of 99%. Moreover, the rGO aerogel demonstrates outstanding compressive strength: the stress of 1.5 MPa under 99% strain and the ratio of strength to density of 177 kPa cm3 mg−1, which overcomes the shortcoming of low stress tolerance for general graphene aerogels. In addition, the rGO aerogel shows high electrical conductivity of 42.7 S m−1 and exceptionally stable current signal response even after tens of thousands of compression cycles under extreme strain (99%). The outstanding properties of this graphene aerogel demonstrate its promising potential as a piezoresistive sensor with high stability and wide detection range.

Compressive performance and fracture mechanism of bio-inspired heterogeneous glass sponge lattice structures manufactured by selective laser melting

High precision lattice structure (LS) shows great potential applications in aerospace, acoustic, biomedical, and wearable products due to its multifunctional characteristics and excellent mechanical properties. Inspired by lightweight, high-strength, and high-stability glass sponges (GSs), a unique circle-/grid-like heterogeneous glass sponge lattice structure (GSLS) was successfully designed and manufactured by selective laser melting (SLM) with Ti6Al4V alloy. Compared with the commonly used body-centred cubic (BCC), face-centred cubic (FCC), honeycomb and diamond LSs, GSLS displays the strongest compressive properties (E = 1560 MPa, σmax = 40 MPa, σy0.2 = 34 MPa, W = 5.95 J). The normalised elastic modulus and normalised compressive strength of GSLS are almost 1.4 and 1.3 times, 2.6 and 2.4 times, 2.7 and 3.5 times, 18 and 8.3 than that of FCC, BCC, honeycomb, and diamond LSs, respectively. Most importantly, unlike the 45° diagonal shear failure of homogeneous BCC and FCC, the FEA simulation reveals that the heterogeneous unit cell in GSLS can enhance the strut connectivity, disperse the stress, and exhibits a unique fracture mechanism of cell-after-cell and layer-by-layer. The fracture mechanism of GSLS can improve the load-bearing capability, maintain strength, and protect its interior and entire integrity during compression.

Impact of growth media and pressure on the diversity and antimicrobial activity of isolates from two species of hexactinellid sponge.

Access to deep-sea sponges brings with it the potential to discover novel antimicrobial candidates, as well as novel cold- and pressure-adapted bacteria with further potential clinical or industrial applications. In this study, we implemented a combination of different growth media, increased pressure and high-throughput techniques to optimize recovery of isolates from two deep-sea hexactinellid sponges, Pheronema carpenteri and Hertwigia sp., in the first culture-based microbial analysis of these two sponges. Using 16S rRNA gene sequencing for isolate identification, we found a similar number of cultivable taxa from each sponge species, as well as improved recovery of morphotypes from P. carpenteri at 22–25 °C compared to other temperatures, which allows a greater potential for screening for novel antimicrobial compounds. Bacteria recovered under conditions of increased pressure were from the phyla Proteobacteria , Actinobacteria and Firmicutes , except at 4 %O2/5 bar, when the phylum Firmicutes was not observed. Cultured isolates from both sponge species displayed antimicrobial activity against Micrococcus luteus, Staphylococcus aureus and Escherichia coli .

Insights into the structure and morphogenesis of the giant basal spicule of the glass sponge Monorhaphis chuni

BackgroundA basal spicule of the hexactinellid sponge Monorhaphis chuni may reach up to 3 m in length and 10 mm in diameter, an extreme case of large spicule size. Generally, sponge spicules are of scales from micrometers to centimeters. Due to its large size many researchers have described its structure and properties and have proposed it as a model of hexactinellid spicule development. Thorough examination of new material of this basal spicule has revealed numerous inconsistencies between our observations and earlier descriptions. In this work, we present the results of detailed examinations with transmitted light and epifluorescence microscopy, SEM, solid state NMR analysis, FTIR and X-ray analysis and staining of Monorhaphis chuni basal spicules of different sizes, collected from a number of deep sea locations, to better understand its structure and function.ResultsThree morphologically/structurally different silica layers i.e. plain glassy layer (PG), tuberculate layer (TL) and annular layer (AL), and an axial cylinder (AC) characterize adult spicules. Young, immature spicules display only plain glassy silica layers which dominate the spicule volume. All three layers i.e. PG, TL and AL can substitute for each other along the surface of the spicule, but equally they are superimposed in older parts of the spicules, with AL being the most external and occurring only in the lower part of the spicules and TL being intermediate between AL and PG. The TL, which is composed of several thinner layers, is formed by a progressive folding of its surface but its microstructure is the same as in the PG layer (glassy silica). The AL differs significantly from the PG and TL in being granular and porous in structure. The TL was found to display positive structures (tubercles), not depressions, as earlier suggested. The apparent perforated and non-perforated bands of the AL are an optical artefact. The new layer type that we called the Ripple Mark Layer (RML) was noted, as well as narrow spikes on the AL ridges, both structures not reported earlier. The interface of the TL and AL, where tubercles fit into depressions of the lower surface of the AL, represent tenon and mortise or dovetail joints, making the spicules more stiff/strong and thus less prone to breaking in the lower part. Early stages of the spicule growth are bidirectional, later growth is unidirectional toward the spicule apex. Growth in thickness proceeds by adding new layers. The spicules are composed of well condensed silica, but the outermost AL is characterized by slightly more condensed silica with less water than the rest. Organics permeating the silica are homogeneous and proteinaceous. The external organic net (most probably collagen) enveloping the basal spicule is a structural element that bounds the sponge body together with the spicule, rather than controlling tubercle formation. Growth of various layers may proceed simultaneously in different locations along the spicule and it is sclerosyncytium that controls formation of silica layers. The growth in spicule length is controlled by extension of the top of the axial filament that is not enclosed by silica and is not involved in further silica deposition. No structures that can be related to sclerocytes (as known in Demospongiae) in Monorhaphis were discovered during this study.ConclusionsOur studies resulted in a new insight into the structure and growth of the basal Monorhaphis spicules that contradicts earlier results, and permitted us to propose a new model of this spicule’s formation. Due to its unique structure, associated with its function, the basal spicule of Monorhaphis chuni cannot serve as a general model of growth for all hexactinellid spicules.

Active Use of Ambient Flow by a Deep-Sea Glass Sponge

How flow moves through porous structures like sponges has long intrigued physical and biological scientists. Despite sponges having specialized cells that function as biological pumps, their porous bodies are proposed to passively take advantage of ambient currents via ‘inducedflow’. This hypothesis relies on the fact that flow external to perforated or tube-like structures drives flow through the structure, but much of the support for this comes from work on dead specimens. A modern understanding of sponge morphology and physiology however, shows that sponges possess a sophisticated sensory system, even in their canals. We used custom flow and oxygen sensors at a 175m deep sponge reef to test the hypothesis of current-induced passive flow through living glass sponges. Evidence to support a passive flow hypothesis was only found in one of six individuals that filtered more water during periods of higher ambient current. As expected, all individuals stopped pumping independently of ambient currents, illustrating their control over pumping using the well-described electrical conduction system. However, at higher ambient currents, sponges removed 30% less oxygen, suggesting a mechanism by which the sponge senses the ambient flow rates and reduces the metabolic expenditure of filtration. The underlying mechanism by which this happens remains unknown, but it may involve a feedback loop through the canals, potentially via primary cilia that have been shown to sense flow in other sponges. Our experiments reveal that while sponges can take advantage of ambient flow, water movement through these animals is controlled by their complex physiology.

Life in the Fast Lane: Modeling the Fate of Glass Sponge Larvae in the Gulf Stream

Effective conservation management of deep-sea sponges, including design of appropriate marine protected areas, requires an understanding of the connectivity between populations throughout a species’ distribution. We provide the first consideration of larval connectivity among deep-sea sponge populations along the southeastern coast of North America, illustrate the influence of the Gulf Stream on dispersal, and complement published distribution models by evaluating colonization potential. Connectivity among known populations of the hexactinellid sponge Vazella pourtalesii was simulated using a 3-D biophysical dispersal model throughout its distribution from Florida, United States to Nova Scotia, Canada. We found no exchange with an estimated pelagic larval duration of 2 weeks between populations north and south of Cape Hatteras, North Carolina at surface, mid-water and seabed release depths, irrespective of month of release or application of a horizontal diffusion constant specific to cross-Gulf Stream diffusivity. The population north of Cape Hatteras and south of Cape Cod was isolated. There was some evidence that Gulf Stream eddies formed near Cape Hatteras could travel to the northwest, connecting the populations in the two sub-regions, however that would require a much longer pelagic duration than what is currently known. More likely almost all larval settlement will be in the immediate area of the adults. At sub-regional scales, connectivity was found from the Strait of Florida through to the Blake Plateau, southeastern United States, with the latter area showing potential for recruitment from more than one source population. The influence of the Charleston Bump, a shallow feature rising from the Blake Plateau, was substantial. Particles seeded just north of the Bump were transported greater distances than those seeded to the south, some of which were caught in an associated gyre, promoting retention at the seabed. To the north on the Scotian Shelf, despite weaker currents and greater distances between known occurrences, unidirectional transport was detected from Emerald Basin to the Northeast Channel between Georges and Browns Banks. These major conclusions remained consistent through simulations run with different averaging periods for the currents (decades to daily) and using two ocean model products (BNAM and GLORYS12V1).

Evolution and phylogeny of glass-sponge-associated zoantharians, with a description of two new genera and three new species

AbstractHexactinellid sponges are important members of deep-sea benthic ecosystems because they provide available hard substrate habitats for filter-feeding invertebrates. However, symbioses between hexactinellid sponges and their symbionts are poorly known. Zoantharians associated with hexactinellid sponges have been reported widely from deep-sea marine ecosystems, either on the bodies or stalks of hexactinellid sponges. Despite these records, there has been a lack of research on their diversity and phylogenetic relationships. In this study, 20 specimens associated with amphidiscophoran and hexasterophoran sponges were collected from the waters of Australia and Japan in the Pacific, and from Curaçao in the southern Caribbean, and these were examined in addition to museum specimens. Based on molecular phylogenetic analyses and morphological observations, we formally describe two new genera and three new species of Zoantharia and report several previously described species. The results suggest at least two independent origins for the symbioses between hexactinellid sponges and zoantharians. Our results demonstrate that the diversity of hexactinellid sponge-associated zoantharians is much higher than has been previously thought. The new taxa described in this work further reconfirm that the deep-sea harbours high levels of undescribed zoantharian diversity.

Revisiting the phosphorite deposit of Fontanarejo (central Spain): new window into the early Cambrian evolution of sponges and the microbial origin of phosphorites

AbstractFossils within early Cambrian phosphorites worldwide are often well preserved due to early diagenetic permineralization. Here, we examine the fossil record contained within phosphorites of the Lower Cambrian Pusa Formation (late Fortunian to Cambrian Stage 2) in Fontanarejo, central Spain. The sedimentology and age of these phosphorites have been controversial and are here reviewed and discussed, providing also an updated geological map. The Pusa Formation is composed of fine clastic sediments that are partly turbiditic, with channels of quartz-rich conglomerates and abundant phosphorites in the upper part of the succession. The microfacies and mineralogy of these channel deposits are studied here for the first time in detail, showing that they are mainly composed of subspherical apatite clasts, with minor mudstone intraclasts, quartzite and mica grains. Numerous sponge spicules, as well as entirely preserved hexactinellid sponges and demosponges, were collected within these phosphorites and likely represent stem groups. In addition to sponges, other fossils, such as small shelly fossils (SSF) of the molluscAnabarellasp., were found. The phosphorites exhibit multiple evidence of intense microbial activity, including diverse fabrics (phosphatic oncoidal-like microbialites, thrombolites, stromatolites and cements) and abundant fossils of filamentous microbes that strongly resemble extant sulphur-oxidizing bacteria. Our findings strongly suggest that microbial processes mediated the rapid formation of most of the Fontanarejo apatite, probably accounting for the exceptional preservation of fragile fossils such as sponge skeletons. The apparent presence of taxonomically diverse hexactinellid and demosponge communities at the lowermost Cambrian further corroborates a Precambrian origin of the phylum Porifera.

The modeled distribution of corals and sponges surrounding the Salas y Gómez and Nazca ridges with implications for high seas conservation.

The Salas y Gómez and Nazca ridges are two adjacent seamount chains off the west coast of South America that collectively contain more than 110 seamounts. The ridges support an exceptionally rich diversity of benthic and pelagic communities, with the highest level of endemism found in any marine environment. Despite some historical fishing in the region, the seamounts are relatively pristine and represent an excellent conservation opportunity to protect a global biodiversity hotspot before it is degraded. One obstacle to effective spatial management of the ridges is the scarcity of direct observations in deeper waters throughout the region and an accompanying understanding of the distribution of key taxa. Species distribution models are increasingly used tools to quantify the distributions of species in data-poor environments. Here, we focused on modeling the distribution of demosponges, glass sponges, and stony corals, three foundation taxa that support large assemblages of associated fauna through the creation of complex habitat structures. Models were constructed at a 1 km2 resolution using presence and pseudoabsence data, dissolved oxygen, nitrate, phosphate, silicate, aragonite saturation state, and several measures of seafloor topography. Highly suitable habitat for each taxa was predicted to occur throughout the Salas y Gómez and Nazca ridges, with the most suitable habitat occurring in small patches on large terrain features such as seamounts, guyots, ridges, and escarpments. Determining the spatial distribution of these three taxa is a critical first step towards supporting the improved spatial management of the region. While the total area of highly suitable habitat was small, our results showed that nearly all of the seamounts in this region provide suitable habitats for deep-water corals and sponges and should therefore be protected from exploitation using the best available conservation measures.

Massive cryptic microbe-sponge deposits in a Devonian fore-reef slope (Elbingerode Reef Complex, Harz Mts., Germany)

A massive occurrence of microbial carbonates, including abundant sponge remains, within the Devonian Elbingerode Reef Complex was likely deposited in a former cavity of the fore-reef slope during the early Frasnian. It is suggested that the formation of microbial carbonate was to a large part favored by the activity of heterotrophic, i.e., sulfate-reducing bacteria, in analogy to Quaternary coral reef microbialites. The Elbingerode Reef Complex is an example of an oceanic or Darwinian barrier reef system. In modern barrier reef settings, microbialite formation is commonly further facilitated by weathering products from the central volcanic islands. The Devonian microbialites of the Elbingerode Reef Complex occur in the form of reticulate and laminated frameworks. Reticulate framework is rich in hexactinellid glass sponges, the tissue decay of which led to the formation of abundant micrite as well as peloidal and stromatactis textures. Supposed calcimicrobes such as Angusticellularia (formerly Angulocellularia) and Frutexites, also known from cryptic habitats, were part of the microbial association. The microbial degradation of sponge tissue likely also contributed to the laminated framework accretion as evidenced by the occurrence of remains of so-called “keratose” demosponges. Further typical textures in the microbialite of the Elbingerode Reef Complex include zebra limestone, i.e., the more or less regular intercalation of microbial carbonate and cement. Elevated concentrations of magnesium in the microbialite as compared to the surrounding metazoan (stromatoporoid-coral) reef limestone suggests that the microbialite of the Elbingerode Reef Complex was initially rich in high-magnesium calcite, which would be yet another parallel to modern, cryptic coral reef microbial carbonates. Deposition and accretion of the microbialite largely occurred in oxygenated seawater with suboxic episodes as indicated by the trace element (REE + Y) data.

Rossellid glass sponges (Porifera, Hexactinellida) from New Zealand waters, with description of one new genus and six new species.

New Zealand’s surrounding deep waters have become known as a diversity hotspot for glass sponges (Porifera: Hexactinellida) in recent years, and description and collection efforts are continuing. Here we report on eight rossellids (Hexasterophora: Lyssacinosida: Rossellidae) collected during the 2017 RV Sonne cruise SO254 by ROV Kiel 6000 as part of Project PoribacNewZ of the University of Oldenburg, Germany. The material includes six species new to science, two of which are assigned to a so far undescribed genus; we further re-describe two previously known species. The known extant rossellid diversity from the New Zealand region is thus almost doubled, from nine species in five genera to 17 species in eight genera. The specimens described here are only a small fraction of hexactinellids collected on cruise SO254. Unfortunately, the first author passed away while working on this collection, only being able to complete the nine descriptions reported here. The paper concludes with an obituary to him, the world-leading expert on glass sponge taxonomy who will be greatly missed.

Mechanical and hydrodynamic analyses of helical strake-like ridges in a glass sponge.

From the discovery of functionally graded laminated composites, to near-structurally optimized diagonally reinforced square lattice structures, the skeletal system of the predominantly deep-sea sponge Euplectella aspergillum has continued to inspire biologists, materials scientists and mechanical engineers. Building on these previous efforts, in the present study, we develop an integrated finite element and fluid dynamics approach for investigating structure-function relationships in the complex maze-like organization of helical ridges that surround the main skeletal tube of this species. From these investigations, we discover that not only do these ridges provide additional mechanical reinforcement, but perhaps more significantly, provide a critical hydrodynamic benefit by effectively suppressing von Kármán vortex shedding and reducing lift forcing fluctuations over a wide range of biologically relevant flow regimes. By comparing the disordered sponge ridge geometry to other more symmetrical strake-based vortex suppression systems commonly employed in infrastructure applications ranging from antennas to underwater gas and oil pipelines, we find that the unique maze-like ridge organization of E. aspergillum can completely suppress vortex shedding rather than delaying their shedding to a more downstream location, thus highlighting their potential benefit in these engineering contexts.