Slime travelers: Early evidence of animal mobility and feeding in an organic mat world

Mobility represents a key innovation in the evolution of complex animal life. The ability to move allows for the exploration of new food sources, escapes from unfavorable environmental conditions, enhanced ability to exchange genetic material, and is one of the major reasons for the diversity and success of animal life today. The oldest widely accepted trace fossils of animal mobility are found in Ediacaran‐aged rocks (635–539 Ma). The earliest definitive evidence for movement associated with exploitation of resources for feeding occurs in the White Sea assemblage of the Ediacara Biota—macroscopic, soft‐bodied fossils of Ediacaran age. Here, we evaluate potential support for mobility in dickinsoniomorphs, presenting new data regarding abundant Dickinsonia and associated trace fossils from the Ediacara Member, South Australia. Results quantitatively demonstrate that Dickinsonia was capable of mobility on relatively short, ecological timescales. This organism was bilaterally symmetrical, likely moved via muscular peristalsis, and left trace fossils due to active removal of the organic mat related to feeding. Analogous structures associated with Yorgia indicate that it was also mobile and fed in a similar manner. Morphological evidence suggests that two other modular taxa, Andiva and Spriggina, were able to move but did not feed in a manner that impacted the organic mat. Together, these data suggest that mobility was present in multiple disparate bilaterally symmetrical Ediacaran taxa.     

Ediacaran developmental biology

Rocks of the Ediacaran System (635–541 Ma) preserve fossil evidence of some of the earliest complex macroscopic organisms, many of which have been interpreted as animals. However, the unusual morphologies of some of these organisms have made it difficult to resolve their biological relationships to modern metazoan groups. Alternative competing phylogenetic interpretations have been proposed for Ediacaran taxa, including algae, fungi, lichens, rhizoid protists, and even an extinct higher‐order group (Vendobionta). If a metazoan affinity can be demonstrated for these organisms, as advocated by many researchers, they could prove informative in debates concerning the evolution of the metazoan body axis, the making and breaking of axial symmetries, and the appearance of a metameric body plan. Attempts to decipher members of the enigmatic Ediacaran macrobiota have largely involved study of morphology: comparative analysis of their developmental phases has received little attention. Here we present what is known of ontogeny across the three iconic Ediacaran taxa Charnia masoni, Dickinsonia costata and Pteridinium simplex, together with new ontogenetic data and insights. We use these data and interpretations to re‐evaluate the phylogenetic position of the broader Ediacaran morphogroups to which these taxa are considered to belong (rangeomorphs, dickinsoniomorphs and erniettomorphs). We conclude, based on the available evidence, that the affinities of the rangeomorphs and the dickinsoniomorphs lie within Metazoa.     

The Homoscleromorph sponge Oscarella lobularis,a promising sponge model in evolutionary and developmental biology

Sponges branch basally in the metazoan phylogenetic tree and are believed to be composed of four distinct lineages with still uncertain relationships. Indeed, some molecular studies propose that Homoscleromorpha may be a fourth Sponge lineage, distinct from Demospongiae in which they were traditionally classified. They harbour many features that distinguish them from other sponges and are more evocative of those of the eumetazoans. They are notably the only sponges to possess a basement membrane with collagen IV and specialized cell‐junctions, thus possessing true epithelia. Among Homoscleromorphs, we have chosen Oscarella lobularis as a model species. This common and easily accessible sponge is characterized by relatively simple histology and cell composition, absence of skeleton, and strongly pronounced epithelial structure. In this review, we explore the specific features that make O. lobularis a promising homoscleromorph sponge model for evolutionary and developmental researches.     

A trophic framework for animal origins

Metazoans emerged in a microbial world and play a unique role in the biosphere as the only complex multicellular eukaryotes capable of phagocytosis. While the bodyplan and feeding mode of the last common metazoan ancestor remain unresolved, the earliest multicellular stem‐metazoans likely subsisted on picoplankton (planktonic microbes 0.2–2 μm in diameter) and dissolved organic matter (DOM), similarly to modern sponges. Once multicellular stem‐metazoans emerged, they conceivably modulated both the local availability of picoplankton, which they preferentially removed from the water column for feeding, and detrital particles 2–100 μm in diameter, which they expelled and deposited into the benthos as waste products. By influencing the availability of these heterotrophic food sources, the earliest multicellular stem‐metazoans would have acted as ecosystem engineers, helping create the ecological conditions under which other metazoans, namely detritivores and non‐sponge suspension feeders incapable of subsisting on picoplankton and DOM, could emerge and diversify. This early style of metazoan feeding, specifically the phagocytosis of small eukaryotic prey, could have also encouraged the evolution of larger, even multicellular, eukaryotic forms less prone to metazoan consumption. Therefore, the first multicellular stem‐metazoans, through their feeding, arguably helped bridge the strictly microbial food webs of the Proterozoic Eon (2.5–0.541 billion years ago) to the more macroscopic, metazoan‐sustaining food webs of the Phanerozoic Eon (0.541–0 billion years ago).     

Phylogenetic Position of the Hexactinellida Within the Phylum Porifera Based on the Amino Acid Sequence of the Protein Kinase C from Rhabdocalyptus dawsoni

Recent analyses of genes encoding proteins typical for multicellularity, especially adhesion molecules and receptors, favor the conclusion that all metazoan phyla, including the phylum Porifera (sponges), are of monophyletic origin. However, none of these data includes cDNA encoding a protein from the sponge class Hexactinellida. We have now isolated and characterized the cDNA encoding a protein kinase C, belonging to the C subfamily (cPKC), from the hexactinellid sponge Rhabdocalyptus dawsoni. The two conserved regions, the regulatory part with the pseudosubstrate site, the two zinc fingers, and the C2 domain, as well as the catalytic domain were used for phylogenetic analyses. Sequence alignment and construction of a phylogenetic tree from the catalytic domains revealed that the yeast Saccharomyces cerevisiae and the protozoan Trypanosoma brucei are at the base of the tree, while the hexactinellid R. dawsoni branches off first among the metazoan sequences; the other two classes of the Porifera, the Calcarea (the sequence from Sycon raphanus was used) and the Demospongiae (sequences from Geodia cydonium and Suberites domuncula were used), branch off later. The statistically robust tree also shows that the two cPKC sequences from the higher invertebrates Drosophila melanogaster and Lytechinus pictus are most closely related to the calcareous sponge. This finding was also confirmed by comparing the regulatory part of the kinase gene. We suggest, that (i) within the phylum Porifera, the class Hexactinellida diverged first from a common ancestor to the Calcarea and the Demospongiae, which both appeared later, and (ii) the higher invertebrates are more closely related to the calcareous sponges. Received: 6 August 1997 / Accepted: 24 October 1997     

From Vendian to Cambrian: the beginning of morphological disparity of modern metazoan phyla

Continuity of the transition from Precambrian to the Phanerozoic metazoan fauna at the phylum level is analyzed. The discrete traces of feeding on bacterial mats by Dickinsonia and similar organisms are explained by extracorporeal digestion, characteristic of a placozoan level of organization, as in the extant Trichoplax. The absence of a morphologically developed anterior end of the body, of food-gathering appendages of any kind, and of appendages responsible for movement suggest that these animals were at this level of organization. Probably, an expanded placozoan level of organization can be assumed for most Vendian animals. Against this background, new characters emerged in the Cambrian to be included in the body plan of extant animal phyla. The relationships between the morphological archetype (body plan) and morphogenetic archetype are considered. It is shown that major features of a morphogenetic archetype could be retained from the time the taxon was formed.     

The oldest labechiid stromatoporoids from intraskeletal crypts in lithistid sponge–Calathium reefs

Early Ordovician (early Floian) reefs of South China include lithistid sponge–Calathium reefs with a three‐dimensional skeletal framework. These structures are among the first post‐Cambrian skeletal‐dominated reef structures and provides an opportunity to test how the novel metazoan builders changed the environments and increased topographic complexity within benthic communities. We document the oldest labechiid stromatoporoid (Cystostroma) in a lithistid sponge–Calathium reef of the Hunghuayuan Formation in southeastern Guizhou, South China. These earliest stromatoporoids may have originated in reefs, and we argue that the complex topography created by the hypercalcified sponge Calathium facilitated the emergence of stromatoporoids. Beyond Cystostroma, keratose sponges, Pulchrilamina (hypercalcified sponge) and bryozoans have also inhabited in the micro‐habitats (cavities and hard substrates) provided by Calathium. These findings suggest that ecosystem engineering by Calathium played an important role in the further diversification of reefs during the Ordovician.     

An unprecedented new genus and family of Tetractinellida (Porifera,Demospongiae) from New Zealand's Colville Ridge,with a new type of mitochondrial group I intron

A remarkable sponge with unprecedented megascleres and systematic affinities was collected recently from a previously unidentified volcano on Colville Ridge to the north‐east of New Zealand. The sponge has the appearance of a tetillid sponge (family Tetillidae Sollas, 1886) with a perfectly spherical external form, radiating internal skeleton of huge oxeas and triaenes, and microspined sigmaspires as microscleres. The triaene megascleres, however, are unprecedented in their form and ornamentation; they are huge clubbed orthotriaenes the upper third of which is acanthose. S tupenda singularis gen. et sp. nov. is described here and the phylogenetic affinity and taxonomic position of this unique sponge is explored in relation to a broad range of tetractinellid sponges (order Tetractinellida Marshall, 1876) using the Folmer + Erpenbeck fragment of the cytochrome c oxidase subunit I (COI) gene and a nearly complete sequence of the 18S rDNA gene. Mitochondrial introns are rare in sponges but S . singularis gen. et sp. nov. possesses a mitochondrial group I intron at position 387 in COI; it hosts a putative LAGLIDADG endonuclease gene. This intron is the first of its kind in sponges: the self‐splicing intron is homologous to a placozoan COI intron whereas the LAGLIDADG endonuclease gene may be related to Fungi LAGLIDADG endonuclease genes. © 2015 The Linnean Society of London     

Molecular phylogeny of the freshwater sponges in Lake Baikal

The phylogenetic relationship of the freshwater sponges (Porifera) in Lake Baikal is not well understood. A polyphyletic and/or monophyletic origin have been proposed. The (endemic) Baikalian sponges have been subdivided into two families: endemic Lubomirskiidae and cosmopolitan Spongillidae. In the present study, two new approaches have been made to resolve the phylogenetic relationship of Baikalian sponges; analysis of (1) nucleotide sequences from one mitochondrial gene, the cytochrome oxidase subunit I (COI) and of (2) one selected intron from the tubulin gene. Specimens from the following endemic Baikalian sponge species have been studied; Lubomirskia baicalensis , Baikalospongia intermedia, Baikalospongia recta , Baikalospongia bacillifera and Swartschewskia papyracea . They are all grouped to the family of Lubomirskiidae. Sequence comparisons were performed with the ubiquitously distributed freshwater sponge Spongilla lacustris (family Spongillidae) as well as with one marine sponge, Suberites domuncula . A sequence comparison * * The sequences reported here are being deposited in the EMBL data base. of the mitochondrial COI gene revealed a monophyletic grouping of the endemic Baikalian sponges with S. lacustris as the most related species to the common ancestor. The sequences of the COI gene from B. recta , B. intermedia , B. bacillifera and L. baicalensis were found to be identical and separated from those of S. lacustris and S. papyracea . In a second approach, the exon/intron sequences framing the intron‐2 of the sponge tubulin gene were chosen for the phylogenetic analysis. The intron sequences were aligned and used for construction of a phylogenetic tree. This analysis revealed again a monophyletic grouping with S. lacustris as the closest related species to the common ancestor. It is concluded that the Baikalian sponges, which have been studied here, are of monophyletic origin. Furthermore, the data suggest that the endemic species S. papyracea is the phylogenetically oldest, extant, endemic Baikalian sponge species.     

Phylogenetic diversity of culturable fungi associated with the Hawaiian Sponges Suberites zeteki and Gelliodes fibrosa

Sponges are well documented to harbor large amounts of microbes. Both culture-dependent and molecular approaches have revealed remarkable bacterial diversity in marine sponges. Fungi are commonly isolated from marine sponges, yet no reports on phylogenetic diversity of sponge-inhabiting fungi exist. In this report, we investigated the phylogenetic diversity of culturable fungi from the Hawaiian alien marine sponges Suberites zeteki and Gelliodes fibrosa. A total of 44 independent isolates were recovered from these two sponge species, representing 7 orders and 22 genera of Ascomycota. The majority (58%) of fungal isolates from S. zeteki resided in the Pleosporales group, while the predominant isolates (52%) from G. fibrosa were members of the Hypocreales group. Though differing in fungal species composition and structure, culturable communities of these two sponges displayed similar phylogenetic diversity. At the genus level, only two genera Penicillium and Trichoderma in the Eurotiales and Hypocreales orders, respectively, were present in both sponge species. The other genera of the fungal isolates were associated with either S. zeteki or G. fibrosa. Some of these fungal genera had been isolated from sponges collected in other marine habitats, but more than half of these genera were identified for the first time in these two marine sponges. Overall, the diversity of culturable fungal communities from these two sponge species is much higher than that observed in studies of marine sponges from other areas. This is the first report of phylogenetic diversity of marine sponge-associated fungi and adds one more dimension to our current understanding of the phylogenetic diversity of sponge-symbiotic microbes.     

ENDOSYMBIOTIC CALCIFYING BACTERIA: A NEW CUE TO THE ORIGIN OF CALCIFICATION IN METAZOA?

Sponges show the highest diversity of associated bacteria among marine invertebrates. Immunological evidence traces the origin of the sponge bacterial symbioses to the Precambrian era. Hence, sponges appear to be ideally suited for studying the evolutionary origins of prokaryote–metazoan associations. Sponges produce either calcareous or siliceous skeletons, which only coexist in a relict group of demosponges, the sclerosponges. We report here, for the first time, intensive calcification in nonsclerosponge siliceous demosponges. Calcification is mediated by endosymbiotic bacteria (calcibacteria) located in archeocyte‐like sponge cells. These calcibacteria are devoid of bacterial walls and divide within sponge cells until they became surrounded by a calcitic sheet, being subsequently extruded to the sponge subectosomal (subepithelial) zone. Thousands of bacteria‐produced calcitic spherules cover the surface of the host sponges, forming a cortex‐like structure that mimics a rudimentary peripheral skeleton. Calcibacteria are vertically transferred to the sponge larvae during embryogenesis. Calcium detoxification may have generated this symbiotic association, with some additional benefits for the sponges, such as skeletal formation and deterrence from predation. This unique symbiosis holds implications for sponge biology and may advance discussions on the role of bacteria in early biocalcification processes in metazoans.     

16S rDNA clone library-based bacterial phylogenetic diversity associated with three South China Sea sponges

Culture-independent molecular techniques, 16S rDNA clone library alongside RFLP and phylogenetic analysis, were applied to investigate the bacterial diversity associated with three South China Sea sponges, Stelletta tenui, Halichondria rugosa and Dysidea avara. A wide bacterial diversity was detected according to total genomic DNA-based 16S rDNA clone library, abundant clones with low identify with sequences retrieved from database were found as well as uncultured sponge symbionts. The phylogenetic analysis shows that the bacterial community structure of Stelletta tenui is similar to that of Halichondria rugosa comprising gamma-Proteobacteria and Firmicutes. Whereas, alpha-Proteobacteria, gamma-Protebacteria, Bacteroidetes and uncultured sponge symbionts were found in sponge Dysidea avara, suggesting that Dysidea avara has the highest bacteria diversity among these sponges. A specific sponge–microbe association is suggested based on the difference of bacterial diversity among these three sponges from the same geography location and the observed sponge species-specific bacteria.     

Evidence for spicule homology in calcareous and siliceous sponges: biminerallic spicules in Lenica sp. from the Early Cambrian of South China

Botting, J.P., Muir, L.A., Xiao, S., Li, X. & Lin, J.‐P. 2012: Evidence for spicule homology in calcareous and siliceous sponges: biminerallic spicules in Lenica sp. from the Early Cambrian of South China. Lethaia, Vol. 45, pp. 463–475. The relationships of the extant sponge classes, and the nature of the last common ancestor of all sponges, are currently unclear. Early sponges preserved in the fossil record differ greatly from extant taxa, and therefore information from the fossil record is critical for testing hypotheses of sponge phylogenetic relationships that are based on modern taxa. New specimens of the enigmatic sponge Lenica sp., from the Early Cambrian Hetang Biota of South China, exhibit an unusual spicule structure. Each spicule consists of a siliceous core with an axial canal, an organic outer layer and a middle layer interpreted to have been originally calcium carbonate. This finding confirms previous work suggesting the existence of biminerallic spicules in early sponges. Combined with data from other early sponges, the new findings imply that the two fundamental spicule structures of modern sponges were derived from a compound, biminerallic precursor. Spicules are therefore homologous structures in Calcarea and Silicea, and if sponges are paraphyletic with respect to Eumetazoa, then spicules may also have been a primitive feature of Metazoa. □Calcarea, Early Cambrian, Hetang Biota, phylogeny, Silicea, taphonomy.     

Glass sponges and bilaterian animals share derived mitochondrial genomic features: a common ancestry or parallel evolution?

Glass sponges (Hexactinellida) are a group of deep-water benthicanimals that have a unique syncytial organization and possessa characteristic siliceous skeleton. Although hexactinellidsare traditionally grouped with calcareous and demosponges inthe phylum Porifera, the monophyly of sponges and the phylogeneticposition of the Hexactinellida remain contentious. We determinedand analyzed the nearly complete mitochondrial genome sequencesof the hexactinellid sponges Iphiteon panicea and Sympagellanux. Unexpectedly, our analysis revealed several mitochondrialgenomic features shared between glass sponges and bilateriananimals, including an Arg Ser change in the genetic code, acharacteristic secondary structure of one of the serine tRNAs,highly derived tRNA and rRNA genes, and the presence of a singlelarge noncoding region. At the same time, glass sponge mtDNAcontains atp9, a gene previously found only in the mtDNA ofdemosponges (among animals), and encodes a with an atypical A11–U24 pair that is alsofound in demosponges and placozoans. Most of our sequence-basedphylogenetic analyses place Hexactinellida as the sister groupto the Bilateria; however, these results are suspect given acceleratedrates of mitochondrial sequence evolution in these groups. Thus,it remains an open question whether shared mitochondrial genomicfeatures in glass sponges and bilaterian animals reflect theirclose phylogenetic affinity or provide a remarkable exampleof parallel evolution.     

Rangeomorphs,Thectardis (Porifera?) and dissolved organic carbon in the Ediacaran oceans

The mid-Ediacaran Mistaken Point biota of Newfoundland represents the first morphologically complex organisms in the fossil record. At the classic Mistaken Point localities the biota is dominated by the enigmatic group of "fractally" branching organisms called rangeomorphs. One of the few exceptions to the rangeomorph body plan is the fossil Thectardis avalonensis, which has been reconstructed as an upright, open cone with its apex in the sediment. No biological affinity has been suggested for this fossil, but here we show that its body plan is consistent with the hydrodynamics of the sponge water-canal system. Further, given the habitat of Thectardis beneath the photic zone, and the apparent absence of an archenteron, movement, or a fractally designed body plan, we suggest that it is a sponge. The recognition of sponges in the Mistaken Point biota provides some of the earliest body fossil evidence for this group, which must have ranged through the Ediacaran based on biomarkers, molecular clocks, and their position on the metazoan tree of life, in spite of their sparse macroscopic fossil record. Should our interpretation be correct, it would imply that the paleoecology of the Mistaken Point biota was dominated by sponges and rangeomorphs, organisms that are either known or hypothesized to feed in large part on dissolved organic carbon (DOC). The biology of these two clades gives insight into the structure of the Ediacaran ocean, and indicates that a non-uniformitarian mechanism delivered labile DOC to the Mistaken Point seafloor.     

Effects of sponge and barnacle encrustation on survival of the scallop <Emphasis Type="Italic">Chlamys hastata</Emphasis>

The scallop Chlamys hastata frequently carries epibionts such as sponges and barnacles on its shells. Although the scallop-sponge relationship has been characterized as a mutualism, little is known about the scallop-barnacle relationship. This study investigated the effects of sponge and barnacle encrustation on the ability of C. hastata to avoid predation by the sea star Pycnopodia helianthoides. In feeding trials, P. helianthoides caught and consumed significantly more barnacle-encrusted scallops (7.7 ± 0.8 out of 20 scallops) than scallops encrusted by either of the sponges Myxilla incrustans (4.1 ± 0.9) or Mycale adhaerens (3.0 ± 0.5). Epibiont-free scallops (5.7 ± 0.5) formed an intermediate treatment between barnacle-encrusted and sponge-encrusted scallops. Possible mechanisms by which the sponges protected the scallops were investigated in two ways: two feeding trials were videotaped to allow qualitative analysis of sea star and scallop behavior and sea star feeding responses to scallop and sponge homogenates were determined to investigate if sea stars accept scallops and sponges as prey. Sea stars displayed positive feeding responses to scallop puree 97.5% ± 1.6 of the time while only displaying positive responses to Mycale adhaerens homogenate 4.4% ± 2.0 of the time and to Myxilla incrustans homogenate 4.4% ± 2.9 of the time. The videotaped feeding trials indicated that interference with tube feet adhesion by the sponge deterred predation. Observations of both sea stars that were videotaped showed that neither avoided trying to capture sponge-encrusted scallops, and at no time was a captured scallop willingly released by the sea stars. Thus, it appears that sponges provide tactile-mechanical protection and possibly chemical or tactile camouflage in this predator/prey relationship. Finally, the effects of sponge encrustation on barnacle settlement were determined. Field experiments showed that barnacle larvae settled more frequently on epibiont-free scallops than on those with either of the two sponges, potentially protecting the scallops from an epibiont that increases the scallop’s susceptibility to predation. Handling editor: K. Martens     

Structural Evidence for the Evolution of Pyrogenic Toxin Superantigens

Cells from metazoan organisms are eliminated in a variety of physiological and pathophysiological processes by apoptosis. In this report, we describe the cloning and characterization of molecules from the marine sponges Geodia cydonium and Suberites domuncula, whose domains show a high similarity to those that are found in molecules of the vertebrate Bcl-2 superfamily and of the death receptors. The Bcl-2 proteins contain up to four Bcl-2 homology regions (BH). Two Bcl-2-related molecules have been identified from sponges that are provided with two of those regions, BH1 and BH2, and are termed Bcl-2 homology proteins (BHP). The G. cydonium molecule, BHP1_GC, has a putative size of 28,164, while the related sequence from S. domuncula, BHP1_SD, has a M _r of 24,187. Phylogenetic analyses of the entire two sponge BHPs revealed a high similarity to members of the mammalian Bcl-2 superfamilies and to the Caenorhabditis elegans Ced-9. When the two domains, BH1 and BH2, are analyzed separately, again the highest similarity was found to the members of the Bcl-2 superfamily, but a clearly lower relationship to the C. elegans BH1 and BH2 domains in Ced-9. In unrooted phylogenetic trees the sponge BH1 and BH2 are grouped among the mammalian sequences and are only distantly related to the C. elegans BH domains. The analysis of the gene structure of the G. cydonium BHP showed that the single intron present is located within the BH2 domain at the same position as in C. elegans and rat Bcl-x_L. In addition, a sponge molecule comprising two death domains has been characterized from G. cydonium. The two death domains of the potential proapoptotic molecule GC_DD2, M _r 24,970, share a high similarity with the Fas-FADD/MORT1 domains. A death domain-containing molecule has not been identified in the C. elegans genome. The phylogenetic analysis revealed that the sponge domain originated from an ankyrin building block from which the mammalian Fas-FADD/MORT1 evolved. It is suggested that the apoptotic pathways that involve members of the Bcl-2 superfamily and of the death receptors are already present in the lowest metazoan phylum, the Porifera. Received: 27 July 1999 / Accepted: 28 December 1999     

Scanning electron microscope evidence for diatom uptake by two Antarctic sponges

Scanning electron microscopy (SEM) investigation of two Antarctic sponges, Phorbas glaberrima and Tedania charcoti, showed that the exopinacoderm effects a direct uptake of benthic diatoms which settle on the sponge surface. In P. glaberrima, planktonic diatoms were also observed penetrating through the inhalant system, the primary way of feeding in sponges. Benthic diatoms which accumulate in the mesohyl underneath the exopinacoderm help to strengthen the sponge cortex and may be an alimentary source during oligotrophic periods in the Antarctic environment.     

Precambrian–Cambrian boundary interval occurrence and form of the enigmatic tubular body fossil Shaanxilithes ningqiangensis from the Lesser Himalaya of India

The affinity of the Ediacaran fossil Shaanxilithes ningqiangensis and putatively related forms has long been enigmatic; over the past few decades, interpretations ranging from trace fossils to algae to metazoans of uncertain phylogenetic placement have been proposed. Combined morphological and geochemical evidence from a new occurrence of S. ningqiangensis in the Krol and Tal groups of the Lesser Himalaya of India indicates that S. ningqiangensis is not a trace fossil, but rather an organic‐walled tubular body fossil of unknown taxonomic affinity. Specimens consist of compressed organic cylindrical structures, characterized by extended, overlapping or fragmented iterated units. Where specimens intersect, overlapping rather than branching or intraplanar crossing is observed. Lithologic comparisons and sequence stratigraphic data all suggest a late Ediacaran age for the uppermost Krol Group and basalmost Tal Group. By extending the biogeographical distribution of S. ningqiangensis, hitherto confined to the Ediacaran of China and potentially Siberia, to the Precambrian–Cambrian boundary interval of India, this new occurrence of S. ningqiangensis expands the biostratigraphic utility of this enigmatic fossil to the inter‐regional and intercontinental scale. Moreover, study of these new and exceptionally preserved samples may help to significantly constrain the long‐debated problem of Shaanxilithes' affinity, elucidating its ‘problematic’ status and shedding new light upon the ecology and taphonomy of one of the most significant intervals in early life history.     

Thermal stress responses in the bacterial biosphere of the Great Barrier Reef sponge,Rhopaloeides odorabile

Marine sponges are diverse, abundant and provide a crucial coupling point between benthic and pelagic habitats due to their high filtration rates. They also harbour extensive microbial communities, with many microbial phylotypes found exclusively in sponge hosts and not in the seawater or surrounding environment, i.e. so‐called sponge‐specific clusters (SCs) or sponge‐ and coral‐specific clusters (SCCs). We employed DNA (16S rRNA gene) and RNA (16S rRNA)‐based amplicon pyrosequencing to investigate the effects of sublethal thermal stress on the bacterial biosphere of the Great Barrier Reef sponge Rhopaloeides odorabile. A total of 8381 operational taxonomic units (OTUs) (97% sequence similarity) were identified, affiliated with 32 bacterial phyla from seawater samples, 23 bacterial phyla from sponge DNA extracts and 18 bacterial phyla from sponge RNA extracts. Sublethal thermal stress (31°C) had no effect on the present and/or active portions of the R. odorabile bacterial community but a shift in the bacterial assemblage was observed in necrotic sponges. Over two‐thirds of DNA and RNA sequences could be assigned to previously defined SCs/SCCs in healthy sponges whereas only 12% of reads from necrotic sponges could be assigned to SCs/SCCs. A rapid decline in host health over a 1°C temperature increment suggests that sponges such as R. odorabile may be highly vulnerable to the effects of global climate change.