Isoswinholide B and swinholide K,potently cytotoxic dimeric macrolides from Theonella swinhoei

Chemical investigation of an Indonesian specimen of Theonella swinhoei afforded the new dimeric macrolides isoswinholide B (5) and swinholide K (6), along with the known swinholides A (1), B (2) and D (3) and isoswinholide A (4). Isoswinholide B showed an unprecedented 21/19′ lactonization pattern, while swinholide K included an sp² methylene attached at C-4 and an additional oxymethine group at C-5, whose configuration has been determined through application of J-based configuration analysis. The isolated swinholides (1–6), with the exception of isoswinholide B, showed a cytotoxic activity on HepG2 (hepatocarcinoma cell line) in the nanomolar range.     

Organism–quartz interactions in structuring benthic communities: towards a marine bio-mineralogy?

Abiotic and biotic factors determine the distribution and structure of marine benthic communities but the processes invoked to explain such patterns are often inadequate. We demonstrate that the presence of quartz grains in sediments inhibits animal colonization on marine soft-bottoms. We suggest that this phenomenon may be related to the oxidant properties of the quartz crystal surface derived by the generation of silicon-based radicals due to water movement. The interaction between organisms and the crystallographic structure of substrata might play a neglected but important role in structuring coastal benthic communities.     

The aquiferous system of two <Emphasis Type="Italic">Oceanapia</Emphasis> species (Porifera,Demospongiae) studied by corrosion casts

The aquiferous systems of two Indopacific Oceanapia species (Oceanapiidae) were studied by corrosion casts: O. amboinensis living in shallow lagoons and O. fistulosa living at the base of the reef slope. Both species show a massive, entirely buried body, emerging from the sediment only by long, completely close fistules. Particularly in O. fistulosa the corrosion casts revealed a complex, grape-like structure of the choanosome organised in anatomical and functional units composed by an incurrent web whose anastomosed meshes are crossed by a central excurrent canal. A system of thin canals connects the two systems giving rise to an area of choanocyte chambers. The corrosion casts revealed that in both species incurrent water penetrates into the sponge body by the fistules and that it is expelled through specialised structures buried in the sediment. This observation is in accordance with field experiments performed on O. fistulosa. In some specimens of this species, a solution of china ink injected into plastic bags enveloping the external fistules was observed, after waiting for a while, to flow through the buried structures.     

Bioerosion features of boring polydorid polychaetes in the North Adriatic Sea

Hydrobiologia - Considering the pivotal role played by erosive organisms in the marine habitat and the scanty knowledge of this phenomenon in the Mediterranean Sea, the present study aimed to...     

Diversity of Porifera in the Mediterranean coralligenous accretions,with description of a new species

Temperate reefs, built by multilayers of encrusting algae accumulated during hundreds to thousands of years, represent one of the most important habitats of the Mediterranean Sea. These bioconstructions are known as “coralligenous” and their spatial complexity allows the formation of heterogeneous microhabitats offering opportunities for a large number of small cryptic species hardly ever considered.Although sponges are the dominant animal taxon in the coralligenous rims with both insinuating and perforating species, this group is until now poorly known. Aim of this work is to develop a reference baseline about the taxonomic knowledge of sponges and, considering their high level of phenotypic plasticity, evaluate the importance of coralligenous accretions as a pocket for biodiversity conservation.Collecting samples in four sites along the coast of the Ligurian Sea, we recorded 133 sponge taxa (115 of them identified at species level and 18 at genus level). One species, Eurypon gracilis is new for science; three species, Paratimea oxeata, Clathria (Microciona) haplotoxa and Eurypon denisae are new records for the Italian sponge fauna, eleven species are new findings for the Ligurian Sea. Moreover, seventeen species have not been recorded before from the coralligenous community. The obtained data, together with an extensive review of the existing literature, increase to 273 the number of sponge species associated with the coralligenous concretions and confirm that this habitat is an extraordinary reservoir of biodiversity still largely unexplored, not only taxonomically, but also as to peculiar adaptations and life histories.     

Desulfohaplosamate, a new phosphate-containing steroid from Dasychalina sp., is a selective cannabinoid CB2 receptor ligand

From the polar organic extract of the Indonesian sponge Dasychalina sp. we have isolated haplosamate A (1), a unique C(28) sterol containing a sulfate group at C-3 and a methyl phosphate at C-15, along with its new desulfo analogue 2, whose structure has been secured by detailed NMR investigation. Compounds 1 and 2, as well as their semi-synthetic analogues 3-5, have been evaluated for interaction with CB(1) and CB(2) receptors through a binding test. Desulfohaplosamate (2) showed a selective affinity for CB(2) receptors in the low μM range, while a semi-synthetic derivative with cleaved ring B showed a complete loss of affinity for both receptors, highlighting the importance of an intact steroid nucleus. To our knowledge, haplosamate derivatives represent the first CB receptor ligands belonging to the class of steroids.     

The aquiferous system of<Emphasis Type="Italic"> Scolymastra joubini</Emphasis> (Porifera,Hexactinellida) studied by corrosion casts

The aquiferous system of the hexactinellid sponge Scolymastra joubini was studied by corrosion casts in specimens from 30 m depth in Terra Nova Bay (Ross Sea, Antarctica). The aquiferous system of hexactinellids is traditionally considered different from that of Demospongiae, lacking a true canal organisation, with water percolating through a trabecular net. The corrosion cast analysis provided evidence that the aquiferous system of S. joubini is characterised by the presence of a system of vessels and not simple spaces or lacunas inside the trabecular net. These vessels constitute incurrent and excurrent ramified structures modularly repeated, respectively, on the external and internal surfaces. This evidence strongly confirms, on a morphological basis, the idea of a unidirectional water flow in Hexactinellida and must be taken into consideration in the study of the phylogenetic relationships between different higher taxa of the Porifera.     

Diatom invasion in the antarctic hexactinellid sponge Scolymastra joubini

Sponges often host large amounts of symbionts, mainly represented by cyanobacteria and dinoflagellates. Recent findings show a widespread presence of symbiotic diatoms living inside antarctic demosponges. In this paper, the invasion by large populations of the diatom Melosira sp. into specimens of the hexactinellid sponge Scolymastra joubini is reported. SEM analyses support the hypothesis that the embedded living diatoms have a negative impact on sponge tissues, leading to degenerative processes. Received: 1 December 1999 / Accepted: 20 February 2000