Nanostructural organization of naturally occurring composites - part II: silica-chitin-based biocomposites

Investigations of the micro- and nanostructures and chemical composition of the sponge skeletons as examples for natural structural biocomposites are of fundamental scientific relevance. Recently, we show that some demosponges (Verongula gigantea, Aplysina sp.) and glass sponges (Farrea occa, Euplectella aspergillum) possess chitin as a component of their skeletons. The main practical approach we used for chitin isolation was based on alkali treatment of corresponding external layers of spicules sponge material with the aim of obtaining alkali-resistant compounds for detailed analysis. Here, we present a detailed study of the structural and physicochemical properties of spicules of the glass sponge Rossella fibulata. The structural similarity of chitin derived from this sponge to invertebrate alpha chitin has been confirmed by us unambiguously using physicochemical and biochemical methods. This is the first report of a silica-chitin composite biomaterial found in Rossella species. Finally, the present work includes a discussion related to strategies for the practical application of silica-chitin-based composites as biomaterials

Recruitment, growth and mortality of an Antarctic hexactinellid sponge, Anoxycalyx joubini.

Polar ecosystems are sensitive to climate forcing, and we often lack baselines to evaluate changes. Here we report a nearly 50-year study in which a sudden shift in the population dynamics of an ecologically important, structure-forming hexactinellid sponge, Anoxycalyx joubini was observed. This is the largest Antarctic sponge, with individuals growing over two meters tall. In order to investigate life history characteristics of Antarctic marine invertebrates, artificial substrata were deployed at a number of sites in the southern portion of the Ross Sea between 1967 and 1975. Over a 22-year period, no growth or settlement was recorded for A. joubini on these substrata; however, in 2004 and 2010, A. joubini was observed to have settled and grown to large sizes on some but not all artificial substrata. This single settlement and growth event correlates with a region-wide shift in phytoplankton productivity driven by the calving of a massive iceberg. We also report almost complete mortality of large sponges followed over 40 years. Given our warming global climate, similar system-wide changes are expected in the future

Molecular evolution of rDNA in early diverging Metazoa

Background: The cytoplasmic ribosomal small subunit (SSU, 18S) ribosomal RNA (rRNA) is the most frequently-used gene for molecular phylogenetic studies. However, information regarding its secondary structure is neglected in most phylogenetic analyses. Incorporation of this information is essential in order to apply specific rRNA evolutionary models to overcome the problem of co-evolution of paired sites, which violates the basic assumption of the independent evolution of sites made by most phylogenetic methods. Information about secondary structure also supports the process of aligning rRNA sequences across taxa. Both aspects have been shown to increase the accuracy of phylogenetic reconstructions within various taxa. Here, we explore SSU rRNA secondary structures from the three extant classes of Phylum Porifera (Grant, 1836), a pivotal, but largely unresolved taxon of early branching Metazoa. This is the first phylogenetic study of poriferan SSU rRNA data to date that includes detailed comparative secondary structure information for all three sponge classes. Results: We found base compositional and structural differences in SSU rRNA among Demospongiae, Hexactinellida (glass sponges) and Calcarea, (calcareous sponges). We showed that analyses of primary rRNA sequences, including secondary structure-specific evolutionary models, in combination with reconstruction of the evolution of unusual structural features, reveal a substantial amount of additional information. Of special note was the finding that the gene tree topologies of marine haplosclerid demosponges, which are inconsistent with the current morphology-based classification, are supported by our reconstructed evolution of secondary structure features. Therefore, these features can provide alternative support for sequencebased topologies and give insights into the evolution of the molecule itself. To encourage and acilitate the application of rRNA models in phylogenetics of early metazoans, we present 52 SSU rRNA secondary structures over the taxonomic range of Porifera in a database, along with some basic tools for relevant format-conversion. Conclusions: We demonstrated that sophisticated secondary structure analyses can increase the potential phylogenetic information of already available rDNA sequences currently accessible in databases and conclude that the importance of SSU rRNA secondary structure information for phylogenetic reconstruction is still generally underestimated, at least among certain early branching metazoans

Mitochondrial genome evolution in the Metazoa: Insights from Class Hexactinellida (Phylum Porifera) and Phylum Cnidaria

Metazoan mitochondrial genomes provide a model system for evolutionary genomic studies. Due to their relatively small size, sequences for complete mitochondrial DNAs (mtDNAs) are now available for animals over a large phylogenetic spectrum, including recent additions for the three classes of Porifera and various cnidarians. This wealth of data gives us a unique opportunity to infer the mechanisms underlying the evolution of genomes. In this dissertation, I will address the example of extensive parallel evolution between two distantly related groups, the Bilateria and Class Hexactinellida (Phylum Porifera; glass sponges), citing the specific examples of degenerated tRNA secondary structures and changes in the genetic code. Much of the plasticity of metazoan mtDNA is linked to the variation of tRNA genes, and I will hypothesize upon the mechanisms that bring about this variation. I will also discuss possible mechanisms involved in the mitochondrial genome reduction of Nematostella vectensis (Class Anthozoa, Phylum Cnidaria), where all but two tRNAs are lost from the mtDNA. Finally, mitochondrial genome data from the Hexactinellida indicates +1 translational frameshifting in protein coding genes, which has only rarely been reported in the mt-genomes of animals. The application of molecular phylogenies both resolves questionable phylogenetic relationships inside Hexactinellida, but also suggests a pattern of evolution for various unusual mt-genomic features

Demospongic Acids Revisited

The well-known fatty acids with a Δ5,9 unsaturation system were designated for a long period as demospongic acids, taking into account that they originally occurred in marine Demospongia sponges. However, such acids have also been observed in various marine sources with a large range of chain-lengths (C16–C32) and from some terrestrial plants with short acyl chains (C18–C19). Finally, the Δ5,9 fatty acids appear to be a particular type of non-methylene-interrupted fatty acids (NMA FAs). This article reviews the occurrence of these particular fatty acids in marine and terrestrial organisms and shows the biosynthetic connections between Δ5,9 fatty acids and other NMI FAs

Compositional and Quantitative Insights Into Bacterial and Archaeal Communities of South Pacific Deep-Sea Sponges (Demospongiae and Hexactinellida)

In the present study, we profiled bacterial and archaeal communities from 13 phylogenetically diverse deep-sea sponge species (Demospongiae and Hexactinellida) from the South Pacific by 16S rRNA-gene amplicon sequencing. Additionally, the associated bacteria and archaea were quantified by real-time qPCR. Our results show that bacterial communities from the deep-sea sponges are mostly host-species specific similar to what has been observed for shallow-water demosponges. The archaeal deep-sea sponge community structures are different from the bacterial community structures in that they are almost completely dominated by a single family, which are the ammonia-oxidizing genera within the Nitrosopumilaceae. Remarkably, the archaeal communities are mostly specific to individual sponges (rather than sponge-species), and this observation applies to both hexactinellids and demosponges. Finally, archaeal 16s gene numbers, as detected by quantitative real-time PCR, were up to three orders of magnitude higher than in shallow-water sponges, highlighting the importance of the archaea for deep-sea sponges in general

Hexactinellida (Porifera) from the Drake Passage (Southern Ocean) with a description of three new species

Goodwin, Claire E., Berman, Jade, Janussen, Dorte, Göcke, Christian, Hendry, Katharine R. (2016): Hexactinellida (Porifera) from the Drake Passage (Southern Ocean) with a description of three new species. Zootaxa 4126 (2): 207-220, DOI: http://doi.org/10.11646/zootaxa.4126.2.

An integrative systematic framework helps to reconstruct skeletal evolution of glass sponges (Porifera, Hexactinellida)

BACKGROUND: Glass sponges (Class Hexactinellida) are important components of deep-sea ecosystems and are of interest from geological and materials science perspectives. The reconstruction of their phylogeny with molecular data has only recently begun and shows a better agreement with morphology-based systematics than is typical for other sponge groups, likely because of a greater number of informative morphological characters. However, inconsistencies remain that have far-reaching implications for hypotheses about the evolution of their major skeletal construction types (body plans). Furthermore, less than half of all described extant genera have been sampled for molecular systematics, and several taxa important for understanding skeletal evolution are still missing. Increased taxon sampling for molecular phylogenetics of this group is therefore urgently needed. However, due to their remote habitat and often poorly preserved museum material, sequencing all 126 currently recognized extant genera will be difficult to achieve. Utilizing morphological data to incorporate unsequenced taxa into an integrative systematics framework therefore holds great promise, but it is unclear which methodological approach best suits this task. RESULTS: Here, we increase the taxon sampling of four previously established molecular markers (18S, 28S, and 16S ribosomal DNA, as well as cytochrome oxidase subunit I) by 12 genera, for the first time including representatives of the order Aulocalycoida and the type genus of Dactylocalycidae, taxa that are key to understanding hexactinellid body plan evolution. Phylogenetic analyses suggest that Aulocalycoida is diphyletic and provide further support for the paraphyly of order Hexactinosida; hence these orders are abolished from the Linnean classification. We further assembled morphological character matrices to integrate so far unsequenced genera into phylogenetic analyses in maximum parsimony (MP), maximum likelihood (ML), Bayesian, and morphology-based binning frameworks. We find that of these four approaches, total-evidence analysis using MP gave the most plausible results concerning congruence with existing phylogenetic and taxonomic hypotheses, whereas the other methods, especially ML and binning, performed more poorly. We use our total-evidence phylogeny of all extant glass sponge genera for ancestral state reconstruction of morphological characters in MP and ML frameworks, gaining new insights into the evolution of major hexactinellid body plans and other characters such as different spicule types. CONCLUSIONS: Our study demonstrates how a comprehensive, albeit in some parts provisional, phylogeny of a larger taxon can be achieved with an integrative approach utilizing molecular and morphological data, and how this can be used as a basis for understanding phenotypic evolution. The datasets and associated trees presented here are intended as a resource and starting point for future work on glass sponge evolution

Occurrence and paleoecological significance of lyssacinosid sponges in the Upper Cretaceous deposits of southern Poland

Cretaceous lyssacinosid sponges (Hexactinellida) are rare and poorly recognized. This is the first description of lyssacinosid sponges from the Cretaceous of Poland. The sponges (including six species and three types of root tufts) come from the Upper Turonian-Lower Coniacian of the Opole Trough, Upper Campanian of the Miechów synclinorium, and Upper Campanian of the SE part of the border synclinorium. All localities lie southwards of the previous reports, widening thus the paleogeographic distribution of the group within the North European Province. Cretaceous lyssacinosids seem to be a useful tool in paleoecological interpretations. The presence of thin-walled lyssacinosids with root tufts indicates a soft substrate, slow rate of sedimentation, and calm and deeper water conditions