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  • 1
    Electronic Resource
    Electronic Resource
    Periods of non-feeding in Polysyncraton lacazei (Ascidiacea: Didemnidae): a rejuvenative process? (1992)
    Springer
    Marine biology 112 (1992), S. 647-655 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Polysyncraton lacazei (Giard) (Ascidiacea: Didemnidae) displays short periods of non-feeding during the warm season in the northwestern Mediterranean Sea (NE of Spain). These periods were analyzed from 1988 to 1990 by monitoring naturally occurring colonies and by morphological and histological observation of non-feeding colonies. During this phase the surface of the colonies is covered by a glassy pellicle and the siphonal apertures are sealed. The phenomenon consists of a reabsorption of the branchial portion of the zooids and a budding of new thoraces. This process does not fit into either the propagative or survival categories of budding proposed for ascidians, and is interpreted as a rejuvenative phenomenon which extends the life span of the zooids.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00346183
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  • 2
    Electronic Resource
    Electronic Resource
    Small-scale association measures in epibenthic communities as a clue for allelochemical interactions (1996)
    Springer
    Oecologia 108 (1996), S. 351-360 
    Details
    ISSN: 1432-1939
    Keywords: Allelopathy ; Spatial competition ; Association ; Epibenthic communities ; Monte Carlo methods
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The small-scale associations in a rocky subtidal community in the northwestern Mediterranean were studied by a development of the continuous line transect method. This method allowed the overall measurement of non-randomness in interspecific contacts and the assignment of an association index to each species-pair, whose, significance was tested by Monte Carlo procedures. At the same time, the continuous recording allowed the study of the weakening of the interactions with increasing distances. Our purpose was to uncover evidence for allelochemical mechanisms of space occupation and maintenance. A strong non-randomness was found in the interspecific associations. This was mostly due to the interactions of the poecilosclerid sponge Crambe crambe (Schmidt) with its neighbours, especially its negative associations with other sponge species. The strength of the relationships fell drastically over the first few centimeters from the contact borders of the different species. The results pointed strongly to an allelochemical mechanism. The extracts of this sponge featured high bioactivity in laboratory assays, and field experiments demonstrated that the sponge can inhibit the growth of species in the community studied. Standard sampling techniques would have overlooked the spatial structure present in the data. The study emphasizes the need for both contact data and distance data in order to identify the underlying processes reliably. The line transect method provides both types of information easily and allows testing of models and identification of organisms likely to use chemical defenses in space competition. Its use as a preliminary step in studies of chemical ecology might help to detect presumptive allelochemical processes prior to experimental work on the potentially active species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00334661
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  • 3
    Electronic Resource
    Electronic Resource
    Natural variation of toxicity in encrusting spongeCrambe crambe (Schmidt) in relation to size and environment (1995)
    Springer
    Journal of chemical ecology 21 (1995), S. 1931-1946 
    Details
    ISSN: 1573-1561
    Keywords: Chemical ecology ; natural toxicity ; spatial variation ; defensive strategy ; encrusting sponges
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The presence of intraspecific variation in toxicity and its relationship with biological or ecological factors were studied in the spongeCrambe crambe. Within-specimen (periphery and central part), between-size (〈1000 mm2 in area, between 1000 and 10,000 mm2 and 〉10,000 mm2) and between-habitat (well-illuminated and dark communities) variations in toxicity were evaluated by the Microtox bioassay. Quantitative differences were detected that were not attributable to within-specimen variation but to size and habitat effects. Habitat comparisons showed that sponges in the shaded habitat were significantly more toxic than those of the well-illuminated community. Sponges of the smaller size classes displayed significantly less toxicity than the medium-sized specimens. Results are interpreted under the optimal defense theory and their ecological implications are considered.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02033853
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  • 4
    Electronic Resource
    Electronic Resource
    Multiple Functions for Secondary Metabolites in Encrusting Marine Invertebrates (1997)
    Springer
    Journal of chemical ecology 23 (1997), S. 1527-1547 
    Details
    ISSN: 1573-1561
    Keywords: Secondary metabolites ; chemical defense ; evolution ; ascidians ; sponges
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract We used three chemical fractions (spanning a wide range of polarities) from the extracts of four marine invertebrates, the spongesCrambe crambe andHemimycale columella and the ascidiansCystodytes dellechiajei andPolysyncraton lacazei, to test inhibition of cell division, photosynthesis, and settlement. We used assay organisms from the same habitat, seeking to determine whether a species may display diverse, ecologically relevant bioac-tivities and, if so, whether the same types of compound may be responsible for such activities. Cell division was strongly inhibited by the spongeC. crambe. A dichloromethane fraction fromC. crambe prevented development of sea urchinParacentrotus lividus eggs at a concentration of 10 μg/ml, as did the butanolic fraction, but at higher concentrations (50 and 100 μg/ml). At 50 μg/ml, the aqueous fraction ofC. crambe allowed cell division but prevented eggs from developing beyond the gastrula stage. Similar results were recorded with the dichloromethane fraction ofP. lacazei and from the aqueous fraction ofH. columella. Photosynthesis was unaffected by any of the species at 50 μg/ml. Larval settlement was inhibited by one or another fraction from the four species surveyed at a concentration of 50 μg/ml, althoughC. crambe exhibited the greatest amount of activity. We therefore found that various fractions displayed the same type of bioactivity, while compounds from the same fraction were responsible for multiple activities, suggesting that secondary metabolites are multiple-purpose tools in nature, which is relevant to our understanding of species ecology and evolution. Moreover, results showed that the assessment of the role of chemical compounds is significantly influenced by the assay organism, fractionation procedure, concentration, and duration of experiments. All these factors should be carefully considered when testing ecological hypotheses of the roles of chemically-mediated bioactivities.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/B:JOEC.0000006420.04002.2e
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  • 5
    Electronic Resource
    Electronic Resource
    Distribution of brominated compounds within the sponge Aplysina aerophoba: coupling of X-ray microanalysis with cryofixation techniques (2000)
    Springer
    Cell & tissue research 301 (2000), S. 311-322 
    Details
    ISSN: 1432-0878
    Keywords: Secondary metabolites Bromine detection Microanalysis Cryotechniques Symbionts Aplysina aerophoba (Spongiae)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. The major secondary metabolites of the sponge Aplysina aerophoba are brominated compounds. X-ray energy dispersive microanalysis was therefore used to locate secondary metabolites via the Br signal in energy emission spectra from sponge sections. To test the reliability of this method in the face of the loss or redistribution of metabolites during processing, we compared the results obtained by conventional aldehyde fixation with those obtained by cryofixation and cryosubstitution with and without cryoembedding. Bromine appeared to be concentrated in two sponge structures, viz. fibres and spherulous cells, when cryofixed material was examined. However, X-ray microanalysis failed to demonstrate the presence of bromine in spherulous cells in chemically fixed samples, showing the need for cryotechniques to avoid the loss of compounds. Cryofixation plus cryosubstitution methods performed best regarding structural preservation and the immobilization of metabolites. The presence of bromine in the spherulous cells suggests that this cell type is the producer of the secondary metabolites, as described for other sponge species. Nevertheless, the presence of bromine in sponge fibres indicates that they can accumulate metabolic substances, although we have been unable to assess whether the chemicals are in their original form or in a modified state within the fibres. A. aerophoba has both bacterial and cyanobacterial symbionts in its mesohyl; the absence of brominated compounds in them contrasts with previous findings in other sponges with prokaryote symbionts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004410000233
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  • 6
    Electronic Resource
    Electronic Resource
    Silica deposition in Demosponges: spiculogenesis in Crambe crambe (2000)
    Springer
    Cell & tissue research 301 (2000), S. 299-309 
    Details
    ISSN: 1432-0878
    Keywords: Silica deposition Spiculogenesis Microanalysis Uultrastructure Sclerocytes Megascleres Crambe crambe (Demospongiae)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. Transmission electron-microscopy images coupled with dispersive X-ray analysis of the species Crambe crambe have provided information on the process of silica deposition in Demosponges. Sclerocytes (megasclerocytes) lie close to spicules or surround them at different stages of growth by means of long thin enveloping pseudopodia. Axial filaments occur free in the mesohyl, in close contact with sclerocytes, and are triangular in cross section, with an internal silicified core. The unit-type membrane surrounding the growing spicule coalesces with the plasmalemma. The axial filament of a growing spicule and that of a mature spicule contain 50%–70% Si and 30%–40% Si relative to that contained in the spicule wall, respectively. The extracellular space between the sclerocyte and the growing spicule contains 50%–65%. Mitochondria, vesicles and dense inclusions of sclerocytes exhibit less than 10%. The cytoplasm close to the growing spicule and that far from the growing spicule contain up to 50% and less than 10%, respectively. No Si has been detected in other parts of the sponge. The megascleres are formed extracellularly. Once the axial filament is extruded to the mesohyl, silicification is accomplished in an extracellular space formed by the enveloping pseudopodia of the sclerocyte. Si deposition starts at regularly distributed sites along the axial filament; this may be related to the highly hydroxylated zones of the silicatein-α protein. Si is concentrated in the cytoplasm of the sclerocyte close to the plasmalemma that surrounds the growing spicules. Orthosilicic acid seems to be pumped, both from the mesohyl to the sclerocyte and from the sclerocyte to the extra-cellular pocket containing the growing spicule, via the plasmalemma.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004410000234
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  • 7
    Electronic Resource
    Electronic Resource
    Chemically-mediated interactions in benthic organisms: the chemical ecology of Crambe crambe (Porifera, Poecilosclerida) (1997)
    Springer
    Hydrobiologia 355 (1997), S. 77-89 
    Details
    ISSN: 1573-5117
    Keywords: Chemical bioactivity ; defence ; toxicity quantification ; toxicity variation ; sponges
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We studied the chemically-mediated interactions of theencrusting sponge Crambe crambe, one of the mosttoxic and widespread species in rocky sublittoralhabitats in the Northwestern Mediterranean. Guanidinealkaloids accounted for C. crambe‘s toxicity,which seems to have multiple functions in nature, asevidence has been found for antifouling,antipredation, and space competition roles.We investigated the factors underlying the chemicaldefence strategy of this species by assessingvariation in the production of toxic substances as afunction of different biological and environmentalvariables. The working hypothesis was that theproduction of these metabolites should be optimizedaccording to the biological features (morphogenesis,reproduction, growth, life history) and ecologicalconditions (biotic pressures and abiotic factors) ofthe particular specimens.One cell type, the spherulous cell, which wasconcentrated near the sponge‘s surface, accumulatedthe toxic substances. Within-specimen analyses showedthat toxicity was higher in the ectosome than in thechoanosome of the sponges. There was a seasonalpattern of change in the toxicity of the species.Life-history stage also proved significant in theproduction of toxic substances: larvae were non-toxic,and feeding-deterrence experiments showed that larvaeand newly metamorphosed individuals were not protectedfrom predation, while two-week-old recruits alreadyshowed strong feeding deterrence. Overall, toxicityincreased from small to medium-sized adult sponges,and decreased again in larger individuals. Variationin toxicity was also found at an ecological level: thevalues at a highly competitive site dominated byslow-growing animal species were higher than those atan adjacent, well-lit site with algal dominance. Therelative investment in structural material (collagen,fibres, spicules...) was also higher in the shadedhabitat, thus a positive relationship was foundbetween investment in chemical and physical defences.In the two habitats compared, allocation to defencecorrelated negatively with reproduction and growth,and positively with survival.The results showed that C. crambe can adjust, atorganismal and population levels, the production ofbioactive substances to different environmental andphysiological situations. Space competition emergedas a key factor explaining the variation found in theproduction of bioactive substances.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1003019221354
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  • 8
    Electronic Resource
    Electronic Resource
    New light on the cell location of avarol within the sponge Dysidea avara (Dendroceratida) (1996)
    Springer
    Cell & tissue research 285 (1996), S. 519-527 
    Details
    ISSN: 1432-0878
    Keywords: Key words: Cell fractionation ; Density gradients ; Secondary metabolites ; Avarol ; Choanocytes ; Sponge ; Dysidea avara (Polifera)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. Many sponges produce and store secondary metabolites with interesting pharmacological bioactivities. Identification of the cell type(s) responsible for the production and/or storage of these compounds may be a crucial step for the future culture and production of these substances if the biosynthesis is not envisageable and the producer organism is rare or too slow-growing for feasible exploitation. Localisation of these cells within the sponge may also contribute to ascertaining the ecological role of these compounds. The cell type containing the main bioactive metabolite (avarol) and its derivative avarone in the sponge Dysidea avara has been identified by cell isolation in a density gradient and by chromatographic techniques. Preliminary cytological characterisation of the cell types in each particular sponge species under study is required, otherwise the identification of the cells in suspensions is inaccurate. In contrast with the findings reported for other sponge species, the active metabolites of D. avara are not contained within spherulous cells but within choanocytes that line the chambers of the aquiferous system. The possible ecological role of avarol is discussed in the light of its internal position and the biological functions of the cells storing the bioactive compounds.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004410050668
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  • 9
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    Enzymatic Kinetics of Cellulose Hydrolysis:  A QCM-D Study (2008)
    American Chemical Society
    Details
    Publication Date: 2008-04-01
    Print ISSN: 0743-7463
    Electronic ISSN: 1520-5827
    Topics: Chemistry and Pharmacology
    Published by American Chemical Society
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  • 10
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    Distribution of brominated compounds within the sponge Aplysina aerophoba : coupling of X-ray microanalysis with cryofixation techniques (2000)
    Springer
    Details
    Publication Date: 2000-07-19
    Print ISSN: 0302-766X
    Electronic ISSN: 1432-0878
    Topics: Biology , Medicine
    Published by Springer
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