Klaus Rützler

The Role of Burrowing Sponges in Bioerosion

SummaryAmong the large number of limestone-eroding organisms, sponges, mainly of the family Clinonidae are of special interest because of their efficient means of substratum penetration by cellular etching and because they release characteristically shaped calcium carbonate chips which can be detected in the mud-size fraction of many sediments. Identifiable trace fossils and sediments are of great ecological and paleoecological significance.As new data on the excavating mechanism have become available, the questions of burrowing rates and sediment production have gained importance. Extrapolation from shortterm experiments (under 6 months) on substrate invasion are inconclusive because of high initial penetration rates resulting from mechanical stimulation and lack of competition. New experiments show that the rate curve flattens after 6 months and that optimum longterm erosion of CaCO3 does not exceed 700 mg m-2 year-1 (Cliona lampa and C. aprica). Substrate limitations and competition will further reduce this rate.By monitoring the production of CaCO3 chips by Cliona lampa, it was possible to link activity patterns to certain environmental factors. Mechanical stimuli, high light intensity, strong currents and, possibly, low temperature seem to accelerate the burrowing process. Sponge-generated chips can make up over 40% of coral mud when deposited in the current shadow of the reef framework.Using transect counts and sponge area-biomass conversion factors, the mean abundance of burrowing sponges on the Bermuda platform could be calculated. On suitable hard bottom substrates it averages 16 g dry weight per m2. From this value the burrowing potential of sponges can be estimated as 256 g CaCO3 per m2 substrate per year. Since 97–98% of the eroded limestone remains in particulate form, the contribution of fine sediments can amount to 250 g m-2 year-1.Attention is called to the fact that erosion rates by burrowers can not directly be compared with those of borers or scrapers. The former are intermittent and their activities are affected by environmental and biological interactions, while activities of the latter are rather constant and guided by the need for food.

The black band disease of Atlantic reef corals. I: Description of the cyanophyte pathogen

Position systematique du nouveau pathogene Phormidium corallyticum. Etude en microscopie electronique

Sponge burrowing: Fine structure of Cliona lampa penetrating calcareous substrata

Cliona lampa Laubenfels (Porifera: Hadromerida), a common burrowing organism in Bermuda, has been used to study the method of sponge penetration into calcareous objects. To progress beyond the results obtained by previous authors, electron-microscope techniques, in addition to light-microscope observations, were employed. Burrowing patterns, fine structure of the tissue-substratum interface and of calcareous fragments removed by sponge activity are described on the basis of scanning electron microscopy. Cell types and cytological features have been identified by light and transmission electron microscope. One cell type of archeocyte origin is demonstrated; it carves out chips of calcium carbonate (and conchiolin) by means of filopodial extensions and etching secretions. The cells undergo plasmolysis during this process; the substratum chips are expelled through the exhalent canal system. It is calculated that only 2 to 3% of the eroded material is removed in solution.

Reconstruction of Family-Level Phylogenetic Relationships within Demospongiae (Porifera) Using Nuclear Encoded Housekeeping Genes

Background Demosponges are challenging for phylogenetic systematics because of their plastic and relatively simple morphologies and many deep divergences between major clades. To improve understanding of the phylogenetic relationships within Demospongiae, we sequenced and analyzed seven nuclear housekeeping genes involved in a variety of cellular functions from a diverse group of sponges. Methodology/Principal Findings We generated data from each of the four sponge classes (i.e., Calcarea, Demospongiae, Hexactinellida, and Homoscleromorpha), but focused on family-level relationships within demosponges. With data for 21 newly sampled families, our Maximum Likelihood and Bayesian-based approaches recovered previously phylogenetically defined taxa: Keratosap, Myxospongiaep, Spongillidap, Haploscleromorphap (the marine haplosclerids) and Democlaviap. We found conflicting results concerning the relationships of Keratosap and Myxospongiaep to the remaining demosponges, but our results strongly supported a clade of Haploscleromorphap+Spongillidap+Democlaviap. In contrast to hypotheses based on mitochondrial genome and ribosomal data, nuclear housekeeping gene data suggested that freshwater sponges (Spongillidap) are sister to Haploscleromorphap rather than part of Democlaviap. Within Keratosap, we found equivocal results as to the monophyly of Dictyoceratida. Within Myxospongiaep, Chondrosida and Verongida were monophyletic. A well-supported clade within Democlaviap, Tetractinellidap, composed of all sampled members of Astrophorina and Spirophorina (including the only lithistid in our analysis), was consistently revealed as the sister group to all other members of Democlaviap. Within Tetractinellidap, we did not recover monophyletic Astrophorina or Spirophorina. Our results also reaffirmed the monophyly of order Poecilosclerida (excluding Desmacellidae and Raspailiidae), and polyphyly of Hadromerida and Halichondrida. Conclusions/Significance These results, using an independent nuclear gene set, confirmed many hypotheses based on ribosomal and/or mitochondrial genes, and they also identified clades with low statistical support or clades that conflicted with traditional morphological classification. Our results will serve as a basis for future exploration of these outstanding questions using more taxon- and gene-rich datasets.

Spatial competition among porifera: Solution by epizoism

SummarySponges settling on solid substrates which are separated by sediment bottoms compete for the limited space. Some species have solved this problem by occurring as epizoans, thus avoiding the risk of being expelled from the habitat. The supporting species on the other hand, are specialized in that they possess skeletogenous ectosomal structures and aquiferous processes to maintain their integrity and to escape starvation or suffocation. Although specimens are sometimes intimately interwoven no chimaerid mixing of tissues was observed.

Endosymbiotic Yeast Maternally Transmitted in a Marine Sponge

The detection of an endosymbiotic yeast in demosponges of the genus Chondrilla described here records the first such association within the phylum Porifera. The symbiont, interpreted as a yolk body in previous ultrastructural studies, is a chitinous-walled fission yeast. Chitin was detected by an immunocytochemical technique that labels its β-1,4-N-acetyl-d-glucosamine residues. Abundant symbiotic yeast cells (4.4 ± 2.3 cells per 10 μm2) transmitted from the soma through the oocytes to the fertilized eggs are directly propagated by vertical transmission in the female. Vertically transmitted yeast were detected in three Chondrilla species with disjunct biogeographical distributions: the Mediterranean, the Caribbean, and the Australian Pacific. Apparently these yeasts are not present in other demosponge genera. Therefore, the fungal endosymbiosis most likely evolved before or during the diversification of the genus Chondrilla.

Siliceous sponge spicules in coral reef sediments

Experimental etching with hydrofluoric acid indicated that silica deposition occurs in a recognizable pattern in common sponge microscleres. The postdepositional alteration of these spicules has previously been generally unrecognized or misinterpreted in the literature. Early stages of postdepositional etching of sponge spicules were observed in the acid insoluble fraction of sediments from the West Atlantic barrier reef near Carrie Bow Cay, Belize. Preliminary data on silica distribution in the Belize barrier reef show that concentrations in fine sediment (<0.25 mm) increase landward of the main reef tract. Sponge spicules are the main component of particulate silica in sediments of the reef and fore-reef where sponge populations abound, whereas grains prevail in the back-reef lagoon deposits. Recycling of locally dissolved silica appears to be important for the growth of many off-shore reef sponges.

Towards a DNA taxonomy of Caribbean demosponges: a gene tree reconstructed from partial mitochondrial CO1 gene sequences supports previous rDNA phylogenies and provides a new perspective on the systematics of Demospongiae

We present the most comprehensive cytochrome oxidase subunit 1 gene tree published to date for demosponges based on new sequences. The CO1 barcoding fragment is sequenced for 65 species from the Caribbean Sea, and its gene tree reconstructed. Although its deeper nodes are not particularly well-supported, the gene tree provides a variety of information for new phylogenetic patterns, as well as support for previously published 28S rDNA gene trees. In our analysis Halichondriidae cluster with Suberitidae, supporting previous 28S rDNA data. Chelae-bearing Poecilosclerida are monophyletic but most taxa lacking chelae in this dataset cluster more distantly. Haplosclerida are not resolved monophyletically under this fragment. While some species exhibit distinct barcodes, some genera contain species that share CO1 haplotypes.

Family Clionaidae D’Orbigny, 1851

Clionaidae (Demospongiae, Hadromerida) receives a new definition by accepting Spheciospongia and massive species previously assigned to Spirastrella (Spirastrellidae). A recently described genus, Cervicornia (for Alcyonium cuspidiferum Lamarck) is included here and distinguished by its specialized incurrent fistules and endopsammic choanosomal pulp. Clionaopsis new name is suggested to replace the preoccupied [Clionopsis] Thiele. Spheciospongia remains distinct for its pore sieves. All other genera are separated by their spicule complements which include tylostyles (with some oxeote or stylote modifications or additions) as megascleres, and delicate (compared to Spirastrellidae) spirasters, amphiasters, smooth and spiny microxeas, and bent or spiral, smooth or spiny microstrongyles and microrhabds as microscleres. Eight genera are considered to be valid.

Lepidocrocite Iron Mineralization in Keratose Sponge Granules

Reddish-brown granules embedded in the spongin fibers of some keratose sponges consist of very fine crystallites of poorly organized lepidocrocite, γ FeOOH. This is the first occurrence of crystalline iron mineralization in the phylum Porifera and the first indication of hard tissue formation among the Keratosa.