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Pei-yuan Qian - One of the best experts on this subject based on the ideXlab platform.
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HSP90 regulates Larval Settlement of the bryozoan Bugula neritina through the nitric oxide pathway.
The Journal of Experimental Biology, 2018Co-Authors: Xiao-xue Yang, Yu Zhang, Yue Him Wong, Pei-yuan QianAbstract:ABSTRACT The larvae of many sessile marine invertebrates go through a Settlement process, during which planktonic larvae attach to a substrate and metamorphose into sessile juveniles. Larval attachment and metamorphosis (herein defined as ‘Settlement’) are complex processes mediated by many signalling pathways. Nitric oxide (NO) signalling is one of the pathways that inhibits Larval Settlement in marine invertebrates across different phyla. NO is synthesized by NO synthase (NOS), which is a client of the molecular chaperone heat shock protein 90 (HSP90). In the present study, we provide evidence that NO, a gaseous messenger, regulates Larval Settlement of Bugula neritina . By using pharmacological bioassays and western blotting, we demonstrated that NO inhibits Larval Settlement of B. neritina and that NO signals occur mainly in the sensory organ of swimming larvae. The Settlement rate of B. neritina larvae decreased after heat shock treatment. Inhibition of HSP90 induced Larval Settlement, and attenuated the inhibition of NO donors during Larval Settlement. In addition, the expression level of both HSP90 and NOS declined upon Settlement. These results demonstrate that HSP90 regulates the Larval Settlement of B. neritina by interacting with the NO pathway.
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The regulatory role of arginine kinase during Larval Settlement of the bryozoan Bugula neritina
Marine Biology, 2018Co-Authors: Yu Zhang, Xiao-xue Yang, Yue Him Wong, Pei-yuan QianAbstract:Larval attachment and metamorphosis, also collectively known as Settlement, plays an important role in the life history of marine invertebrates with biphasic life cycle. Bugula neritina can settle on any substrate without substrate selection. This complex transformation usually involves an active selection process, while the Larval decision to settle is regulated by both exogenous and endogenous factors. This study focuses on the involvement of arginine kinase (AK), an important enzyme that regulates energy metabolism in marine invertebrates, during Larval Settlement of the bryozoan Bugula neritina. We reveal that AK was highly expressed in the swimming larvae of B. neritina, while its expression was down-regulated post-attachment. When treated with AK inhibitors, the Larval Settlement rate was significantly decreased. In addition, the immunostaining results indicated that AK was mainly localized to the neuro-muscular cord in swimming larvae. Overall, our results suggest the involvement of AK in regulating Larval Settlement of B. neritina.
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Comparative Transcriptomic Analysis Reveals Candidate Genes and Pathways Involved in Larval Settlement of the Barnacle Megabalanus volcano
International journal of molecular sciences, 2017Co-Authors: Guoyong Yan, Zhang, Jin Sun, Jiao-mei Huang, Yi Lan, Cong Zeng, Yong Wang, Pei-yuan QianAbstract:Megabalanus barnacle is one of the model organisms for marine biofouling research. However, further elucidation of molecular mechanisms underlying Larval Settlement has been hindered due to the lack of genomic information thus far. In the present study, cDNA libraries were constructed for cyprids, the key stage for Larval Settlement, and adults of Megabalanus volcano. After high-throughput sequencing and de novo assembly, 42,620 unigenes were obtained with a N50 value of 1532 bp. These unigenes were annotated by blasting against the NCBI non-redundant (nr), Swiss-Prot, Cluster of Orthologous Groups (COG), and Kyoto Encyclopedia of Genes and Genomes (KEGG) databases. Finally, 19,522, 15,691, 14,459, and 10,914 unigenes were identified correspondingly. There were 22,158 differentially expressed genes (DEGs) identified between two stages. Compared with the cyprid stage, 8241 unigenes were down-regulated and 13,917 unigenes were up-regulated at the adult stage. The neuroactive ligand-receptor interaction pathway (ko04080) was significantly enriched by KEGG enrichment analysis of the DEGs, suggesting that it possibly involved in Larval Settlement. Potential functions of three conserved allatostatin neuropeptide-receptor pairs and two light-sensitive opsin proteins were further characterized, indicating that they might regulate attachment and metamorphosis at cyprid stage. These results provided a deeper insight into the molecular mechanisms underlying Larval Settlement of barnacles.
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Characterization of Arginine Kinase in the Barnacle Amphibalanus Amphitrite and Its Role in the Larval Settlement.
Journal of experimental zoology. Part B Molecular and developmental evolution, 2016Co-Authors: Zhang, Xiao-xue Yang, Yu Zhang, Yue Him Wong, Jin Sun, Guoyong Yan, Pei-yuan QianAbstract:Energy metabolism is a key process in Larval Settlement of barnacles, but the underlying molecular mechanisms remain ambiguous. Arginine kinase (AK) mainly participates in energy metabolism in invertebrates. So far, its roles in barnacles have not been studied. In the present study, we raised an antibody against AK from Amphibalanus amphitrite Darwin to characterize the roles of AK in the Larval Settlement process. Among the developmental stages, AK was highly expressed during the cypris stage. Along with the aging process in cyprids, the level of AK decreased. The immunostaining results showed that AK was localized to muscular tissues in cyprids, including antennules, antennular muscles, and thoracic limbs. The Larval Settlement rate decreased and Larval movement was inhibited in response to treatments with high concentrations of AK inhibitors (rutin and quercetin). These results demonstrated that AK was involved in the Larval Settlement of A. amphitrite through mediating energy supply in muscle tissues. Moreover, further analysis indicated that both the p38 MAPK and NO/cGMP pathways positively mediated the expression of AK in cyprids.
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Cochliomycin A inhibits the Larval Settlement of Amphibalanus amphitrite by activating the NO/cGMP pathway.
Biofouling, 2016Co-Authors: Kai-ling Wang, Zhang, Jin Sun, Zhuang Han, Ling-li Liu, Chang-lun Shao, Qing-ai Liu, Chang-yun Wang, Pei-yuan QianAbstract:Cochliomycin A is a compound with anti-barnacle Settlement activity and low toxicity, but the molecular mechanism of the compound is unknown. Here, isobaric tags for the relative or absolute quantitation (iTRAQ) labeling proteomic method were applied to analyze changes in the proteome of Amphibalanus (=Balanus) amphitrite cyprids in response to cochliomycin A treatment. Cochliomycin A affected the cytochrome P450, glutathione S-transferase (GST) and NO/cGMP pathways, among which the NO/cGMP pathway was considered to play a key role in barnacle Larval Settlement, while the cytochrome P450 and the GST pathways are mainly for detoxification. The results of real-time PCR further suggested the NO/cGMP pathway was activated in response to cochliomycin A. Larval Settlement assays revealed that S-methylisothiourea sulfate (SMIS) and 1H-(1,2,4)oxadiazolo[4,3-a]quinoxalin-1-one (ODQ) rescued cyprids from cochliomycin A-induced inhibition of Larval Settlement. The findings supported the hypothesis that cochliomycin A inhibited barnacle Larval Settlement by stimulating the NO/cGMP pathway.
Tilmann Harder - One of the best experts on this subject based on the ideXlab platform.
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Crustose coralline algae that promote coral Larval Settlement harbor distinct surface bacterial communities
Coral Reefs, 2020Co-Authors: Nahshon Siboni, David Abrego, Eneour Puill-stephan, William L. King, David G. Bourne, Jean-baptiste Raina, Justin R. Seymour, Tilmann HarderAbstract:Most benthic invertebrates, including ecosystem engineers such as corals, sponges and bivalves, have a motile planktonic Larval phase and rely on specific chemical cues to identify a suitable substrate to settle. Crustose coralline algae (CCA) can induce Settlement and metamorphosis responses in many invertebrates including corals. We tested the respective coral Settlement capacity of multiple CCA species in a choice experiment and investigated the composition of their microbiomes. Our findings revealed that coral Larval Settlement was drastically influenced by CCA genera and also suggest that bacterial communities on the CCA surface can potentially serve as a driver of coral Larval Settlement. The composition of the bacterial communities on the surface of the least attractive CCA genus, Neogoniolithon fosliei , was markedly different from the other genera, Porolithon gardineri and Titanoderma prototypum and was significantly enriched in Vibrio and Flammeovirgaceae . The activity of CCA-associated bacterial communities may contribute to some of the variability observed in Settlement responses between CCA species. Specific bacterial ASVs assigned to the Neptuniibacter , Methylotrophic Group 3 and Cellvibrionaceae were positively correlated with coral Settlement. Conversely, ASVs assigned as Vibrio and Flammeovirga were negatively correlated with coral Settlement. This study identifies putative bacterial taxa involved in coral Settlement, which is an essential step to understand the chemical cues involved in this process and to predict the ability of corals to recolonize damaged reefs following disturbances.
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Single-species bacteria in sediments induce Larval Settlement of the infaunal polychaetes Polydora cornuta and Streblospio benedicti
Marine Biology, 2013Co-Authors: Zita Sebesvari, Rebecca Neumann, Thorsten Brinkhoff, Tilmann HarderAbstract:Larval Settlement of the infaunal spionid polychaetes Polydora cornuta and Streblospio benedicti is mediated by sediment-associated microorganisms. To investigate if Larval preference for certain sediment is guided by individual sediment-associated bacteria, 13 bacterial isolates (5 phyla) obtained from the natural habitat of adult polychaetes (Wadden Sea, Germany) in 2008 were screened in still-water, no-choice Settlement assays. Two isolates (α-Proteobacterium-Strain DF11 and Flavobacterium-Strain 54) significantly triggered Larval Settlement in comparison with sterile sediment. In still-water, multiple-choice Settlement assays comprising natural and sterile sediment and sediment re-inoculated with isolates DF11 and 54, significant preferences for natural sediment and sediment containing bacterial isolates at 108 cells g−1 were observed. Larval Settlement was influenced by bacterial abundance in sediment but the correlation was not strictly positive; thus, maximum Larval Settlement in response to single bacterial species may occur at certain optimum densities. Non-viable or suspended bacteria and water-soluble bacterial products did not induce Larval Settlement, suggesting that sediment-associated bacterial Settlement cues for P. cornuta and S. benedicti were either produced in situ and/or consisted of heat-labile bacterial products.
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Effects of halogenated metabolites from infaunal polychaetes on Larval Settlement of the spionid polychaete Streblospio benedicti
Marine Ecology Progress Series, 2008Co-Authors: Ferdinand Esser, Zita Sebesvari, M. Winterberg, Tilmann HarderAbstract:Considering that a variety of infaunal polychaetes release halogenated metabolites with potent bactericidal effects into the surrounding sediment, we tested the hypothesis that polychaete- derived halometabolites may either pose a direct negative effect on larvae or alter the bacterial com- munity in surface sediments, and thus indirectly influence Larval Settlement. Commercially available halogenated compounds identical or similar to the dominant halometabolites found in Streblospio benedicti and Capitella sp. I served as experimental proxies in single- and multiple-choice Settlement assays with larvae of S. benedicti. In multiple-choice assays, the hypothesis of a direct influence of halogenated proxies on Larval Settlement was verified with 1-chlorononane at concentrations of 3.5 µg g -1 sediment. A similar effect was not observed with 2,6-dibromophenol. The no-choice assays did not show a direct influence of halometabolites on polychaete larvae. On the other hand, the hypothesis of an indirect influence of halogenated proxies on Larval Settlement via modification of the sediment microbial assemblage was clearly rejected. However, an analysis of similarity of the PCR-amplified bacterial genes coding for 16S rRNA corresponding to distinct phylotypes revealed a significant change in bacterial community richness between untreated and natural sediment spiked and incubated with halogenated proxies for 7 d. The change was characterized by the absence of up to 13 phylotypes and the appearance of up to 11 previously undetected phylotypes. The shift in bacterial community richness of sediments exposed to the halogenated proxies was not recognized by larvae, indicating that the halogenated proxies elicited no differential response in larvae of S. benedicti.
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Sediment-associated cues for Larval Settlement of the infaunal spionid polychaetes Polydora cornuta and Streblospio benedicti
Journal of Experimental Marine Biology and Ecology, 2006Co-Authors: Zita Sebesvari, Ferdinand Esser, Tilmann HarderAbstract:Do patchy distribution patterns of infaunal polychaetes result from active site selection of larvae influenced by sedimentassociated microbial cues? This hypothesis was tested with still-water laboratory Settlement assays revealing the acceptance or rejection of polychaete larvae to qualitatively different sediments. Laboratory brood cultures of the spionid polychaetes Polydora cornuta and Streblospio benedicti yielded a sufficient number of larvae with planktotrophic development for bioassays. High Settlement rates (75–95%) of test larvae were observed in response to natural sediment. Sterilization of natural sediment significantly decreased Settlement of P. cornuta (25–55%) while combustion of sediment significantly decreased the Settlement rate in both species (5–50%). Differences in Settlement responses to sediments treated by sterilization or combustion most likely resulted from a variety of factors such as modified sediment fabric, grain size distribution and quantity of adsorbed organic matter. To experimentally address the potential role of microorganisms and microbial metabolites as mediators of Larval Settlement, ashed sediment was inoculated with viable microorganisms obtained from natural sediment. In both polychaete species, this treatment significantly increased Larval Settlement in comparison to the control of ashed sediment indicating that Larval Settlement was at least partially mediated by the presence of microorganisms associated with sediment.
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Induction of Larval Settlement in the polychaete Hydroides elegans by extracellular polymers of benthic diatoms
Marine Ecology Progress Series, 2005Co-Authors: Cindy Lam, Tilmann Harder, Pei-yuan QianAbstract:Larval Settlement of the polychaete Hydroides elegans Haswell, 1883 is mediated by marine biofilms; complex agglomerates of bacteria, diatoms, fungi and protozoa enmeshed in a matrix of extracellular polymers (EPS). In our previous investigations, benthic diatoms were demon- strated to be potent mediators of Larval Settlement in H. elegans. The putative diatom-derived settle- ment cues were heat-stable components in close association with the diatom surface. For an in-depth investigation of the chemical nature of diatom-derived Larval Settlement cues, the EPS of the induc- tive (Achnanthes sp., Nitzschia constricta) and non-inductive (Amphora tenerrima, Nitzschia frustu- lum) diatoms were bioassayed for their effect on Larval Settlement. When EPS fractions larger than 100 kDa were immobilized in stable hydrogels to mimic their association to a solid substratum, they evoked an effect on Larval Settlement similar to that of the respective monospecies diatom films. The crude exopolymer samples mainly consisted of polysaccharides with a small proportion of proteina- ceous sample components. After enzymatic removal of proteinaceous EPS components, the samples evoked an effect on Larval Settlement similar to that of the crude EPS samples, indicating the negligible role of large proteins or glycoproteins as Settlement cues.
Stanley C.k. Lau - One of the best experts on this subject based on the ideXlab platform.
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Induction of Larval Settlement in the serpulid polychaete Hydroides elegans (Haswell): role of bacterial extracellular polymers.
Biofouling, 2003Co-Authors: Stanley C.k. Lau, Tilmann Harder, Pei-yuan QianAbstract:Larval Settlement in the marine polychaete Hydroides elegans is effectively mediated upon contact with the surface of marine bacterial films. Using the bacterium Roseobacter litoralis as a model strain, the effect of bacterial extracellular polymers (exopolymers) on Larval Settlement of H. elegans was investigated. Bioassays with exopolymer fractions dissociated from bacterial films evoked the initial stages of the Larval Settlement process, i.e. larvae slowed down, secreted a mucous thread and crawled over the surface. This response is typical of larvae that encounter an attractive bacterial film. In contrast, bioassays with exopolymers in association with UV-irradiated, metabolically inactive bacterial films evoked complete Settlement. However, the percentage of responding larvae was negatively correlated with the magnitude of UV-dosage. Since UV energy crosslinks both intra- and extracellular proteinaceous components, it could not be distinguished whether the decrease in Larval Settlement was due to a modification of proteinaceous components of exopolymers or due the elimination of cellular activity. Nevertheless, the results ascribe bacterial exopolymers the role of an indicator of substratum suitability and provide evidence that the polysaccharide moiety of exopolymers does not complement this effect.
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bioactivity of bacterial strains isolated from marine biofilms in hong kong waters for the induction of Larval Settlement in the marine polychaete hydroides elegans
Marine Ecology Progress Series, 2002Co-Authors: Stanley C.k. Lau, Karen K W Mak, Feng Chen, Pei-yuan QianAbstract:In the present study, 38 bacterial isolates were obtained from a marine biofilm, identi- fied by the comparison of 16S rRNA gene sequences, and investigated by laboratory bioassays for their effects on Larval Settlement of the marine polychaete Hydroides elegans (Haswell). The bacter- ial isolates belonged to 3 phylogenetic branches: γ-Proteobacteria (26 isolates), Gram-positive (8 iso- lates) and Cytophaga-Flexibacter-Bacteroides (4 isolates). Most of the isolates were affiliated to the genera Vibrio (7 isolates), Alteromonas (8 isolates) or Pseudoalteromonas (8 isolates), which are in the γ-Proteobacteria branch. According to their efficacy to induce Larval Settlement of H. elegans in lab- oratory bioassays, the isolates were categorized as strongly, moderately, and non-inductive for Larval Settlement. About 42% of the isolates were categorized as non-inductive and the rest of the isolates contained equal numbers of highly and moderately inductive strains. The results indicated that lar- val Settlement of H. elegans could be induced by bacteria in a wide range of taxa. The isolates that induced high and moderate levels of Larval Settlement belonged to the genus Cytophaga in the Cytophaga-Flexibacter-Bacteroides branch; the genera Bacillus, Brevibacterium, Micrococcus and Staphylococcus in the Gram-positive branch; and the genera Alteromonas, Pseudoalteromonas and Vibrio in the γ-Proteobacteria branch. Results also showed that isolates affiliating to the same genus might have tremendously different activities for the induction of Larval Settlement. For example, isolates that were affiliated to the genus Alteromonas or Pseudoalteromonas distributed over the 3 categories of activity for induction of Larval Settlement.
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Isolation of bacterial metabolites as natural inducers for Larval Settlement in the marine polychaete Hydroides elegans (Haswell).
Journal of Chemical Ecology, 2002Co-Authors: Tilmann Harder, Stanley C.k. Lau, Hans-uwe Dahms, Pei-yuan QianAbstract:The bacterial component of marine biofilms plays an important role in the induction of Larval Settlement in the polychaete Hydroides elegans. In this study, we provide experimental evidence that bacterial metabolites comprise the chemical signal for Larval Settlement. Bacteria were isolated from biofilms, purified and cultured according to standard procedures. Bacterial metabolites were isolated from spent culture broth by chloroform extraction as well as by closed-loop stripping and adsorption of volatile components on surface-modified silica gel. A pronounced biological activity was exclusively observed when concentrated metabolites were adsorbed on activated charcoal. Larvae did not respond to waterborne metabolites when prevented from contacting the bacterial film surface. These results indicate that an association of the chemical signal with a sorbent-like substratum may be an essential cofactor for the expression of biological activity. The functional role of bacterial exopolymers as an adsorptive matrix for Larval Settlement signals is discussed.
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Larval Settlement in the serpulid polychaete Hydroides elegans in response to bacterial films: An investigation of the nature of putative Larval Settlement cue
Marine Biology, 2001Co-Authors: Stanley C.k. Lau, Pei-yuan QianAbstract:Larval Settlement in the marine polychaete Hydroides elegans (Haswell) is induced by certain bacteria in marine biofilms. The exact nature of the Settlement cue that larvae of H. elegans receive from these bacteria remains unknown. In this study, we revealed some properties of the bacterially derived Larval Settlement cue by investigating the Larval Settlement inductive activity of two bacterial strains after various treatments. These two bacterial strains, Roseobacter sp. and an α-subclass Proteobacteria, are highly inductive to Larval Settlement of H. elegans. The larvae responded similarly to Roseobacter and Proteobacteria in all the Larval Settlement bioassays, suggesting that the Larval Settlement-inducing substances produced by these bacteria may share common characteristics. First of all, the larvae did not settle in the seawater conditioned by the bacteria attached as a film or by the bacteria that were freely suspended in seawater. The results suggest that the putative Larval Settlement cue is not released into seawater and, therefore, should be associated with the surface of the bacteria. Secondly, formaldehyde treatment entirely eliminated the Larval Settlement induction activity of the bacterial films, and streptomycin treatment reduced the percentage of Larval Settlement on the bacterial films in a concentration-dependent manner. Since both treatments can kill bacteria with little damage to the surface chemistry of bacterial cells, the decline in Larval Settlement is suggested be due to a reduction of the viable bacterial population in the bacterial films. In fact, the reduction of Larval Settlement in the streptomycin treatments coincided with the decrease in viable bacterial populations in broth cultures containing respective concentrations of streptomycin. These results suggest that the viability of Roseobacter and Proteobacteria is important to their Settlement induction effect. Since the Larval Settlement induction activity of the bacterial strains appears to correlate with their viability, we suggest that the putative Larval Settlement cue is derived from a metabolic pathway in the bacteria and that the cue is exported to and concentrated at the extracellular polymer matrix of the bacterial cell, at which the larvae establish contact with the bacteria. The Larval Settlement cue may be highly susceptible to degradation so that a metabolically active bacterial film is needed to maintain the putative cue at a concentration that surpasses the threshold for induction of Larval Settlement.
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Phlorotannins and related compounds as Larval Settlement inhibitors of the tube-building polychaete Hydroides elegans
Marine Ecology Progress Series, 1997Co-Authors: Stanley C.k. Lau, Pei-yuan QianAbstract:This study examined the inhibition of Hydroides elegans Larval Settlement by brown algal phlorotannins as well as 2 related compounds, tannic acid and phloroglucinol. Two mechanisms have been suggested to explain the antifouling effects of natural compounds: natural compounds may target macrofoulers directly, or they may regulate the growth of microfoulers, such as bacteria, which in turn affects Larval Settlement. We hypothesized that phlorotannins, phloroglucinol and tannic acid inhibit H. elegans Larval Settlement through both mechanisms. In this study, we investigated (1) the LC5, of the 3 compounds on H. elegans larvae, (2) the EC,,, for inhibition of H. elegans Larval Settlement by the 3 compounds, (3) antibacterial activity of the 3 compounds, and (4) Settlement of H. elegans larvae on both monospecies and multispecies bacterial films. Twelve different strains of marine bacteria were isolated for antibiosis assays and Larval Settlement assays. Our results indicated that phlorotannins, tannic acid, and phloroglucinol were inhibitory to H. elegans Larval Settlement and to the growth of certain marine bacteria. Assays of Larval Settlement on bactenal films revealed that H. elegans larvae settled differentially on different species of bacteria. Changes in either bacterial species or ratio of bacterial species in multispecies bacterial films also affected H. elegans Larval Settlement. An integration of results from the antibiosis assays together with those from the assays of Larval Settlement on bacterial films revealed that phlorotannins and the related compounds were inhibitory to some of the bacterial species that induced high levels of H. elegans Larval Settlement; however, some of the bacteria that induced low levels of H. elegans Larval Settlement were resistant to the compounds. Therefore, we speculate that the bacteria which induce high level of H. elegans Larval Settlement may be lacking in a biofilm that is developed under the influence of the compounds, and the niches become available to the phenolic-resistant bacteria that cause low levels of H. elegans Larval Settlement. Consequently, the phenolic-treated biofilm may become unfavorable to H. elegans Larval Settlement.
Zita Sebesvari - One of the best experts on this subject based on the ideXlab platform.
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Single-species bacteria in sediments induce Larval Settlement of the infaunal polychaetes Polydora cornuta and Streblospio benedicti
Marine Biology, 2013Co-Authors: Zita Sebesvari, Rebecca Neumann, Thorsten Brinkhoff, Tilmann HarderAbstract:Larval Settlement of the infaunal spionid polychaetes Polydora cornuta and Streblospio benedicti is mediated by sediment-associated microorganisms. To investigate if Larval preference for certain sediment is guided by individual sediment-associated bacteria, 13 bacterial isolates (5 phyla) obtained from the natural habitat of adult polychaetes (Wadden Sea, Germany) in 2008 were screened in still-water, no-choice Settlement assays. Two isolates (α-Proteobacterium-Strain DF11 and Flavobacterium-Strain 54) significantly triggered Larval Settlement in comparison with sterile sediment. In still-water, multiple-choice Settlement assays comprising natural and sterile sediment and sediment re-inoculated with isolates DF11 and 54, significant preferences for natural sediment and sediment containing bacterial isolates at 108 cells g−1 were observed. Larval Settlement was influenced by bacterial abundance in sediment but the correlation was not strictly positive; thus, maximum Larval Settlement in response to single bacterial species may occur at certain optimum densities. Non-viable or suspended bacteria and water-soluble bacterial products did not induce Larval Settlement, suggesting that sediment-associated bacterial Settlement cues for P. cornuta and S. benedicti were either produced in situ and/or consisted of heat-labile bacterial products.
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Effects of halogenated metabolites from infaunal polychaetes on Larval Settlement of the spionid polychaete Streblospio benedicti
Marine Ecology Progress Series, 2008Co-Authors: Ferdinand Esser, Zita Sebesvari, M. Winterberg, Tilmann HarderAbstract:Considering that a variety of infaunal polychaetes release halogenated metabolites with potent bactericidal effects into the surrounding sediment, we tested the hypothesis that polychaete- derived halometabolites may either pose a direct negative effect on larvae or alter the bacterial com- munity in surface sediments, and thus indirectly influence Larval Settlement. Commercially available halogenated compounds identical or similar to the dominant halometabolites found in Streblospio benedicti and Capitella sp. I served as experimental proxies in single- and multiple-choice Settlement assays with larvae of S. benedicti. In multiple-choice assays, the hypothesis of a direct influence of halogenated proxies on Larval Settlement was verified with 1-chlorononane at concentrations of 3.5 µg g -1 sediment. A similar effect was not observed with 2,6-dibromophenol. The no-choice assays did not show a direct influence of halometabolites on polychaete larvae. On the other hand, the hypothesis of an indirect influence of halogenated proxies on Larval Settlement via modification of the sediment microbial assemblage was clearly rejected. However, an analysis of similarity of the PCR-amplified bacterial genes coding for 16S rRNA corresponding to distinct phylotypes revealed a significant change in bacterial community richness between untreated and natural sediment spiked and incubated with halogenated proxies for 7 d. The change was characterized by the absence of up to 13 phylotypes and the appearance of up to 11 previously undetected phylotypes. The shift in bacterial community richness of sediments exposed to the halogenated proxies was not recognized by larvae, indicating that the halogenated proxies elicited no differential response in larvae of S. benedicti.
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Sediment-associated cues for Larval Settlement of the infaunal spionid polychaetes Polydora cornuta and Streblospio benedicti
Journal of Experimental Marine Biology and Ecology, 2006Co-Authors: Zita Sebesvari, Ferdinand Esser, Tilmann HarderAbstract:Do patchy distribution patterns of infaunal polychaetes result from active site selection of larvae influenced by sedimentassociated microbial cues? This hypothesis was tested with still-water laboratory Settlement assays revealing the acceptance or rejection of polychaete larvae to qualitatively different sediments. Laboratory brood cultures of the spionid polychaetes Polydora cornuta and Streblospio benedicti yielded a sufficient number of larvae with planktotrophic development for bioassays. High Settlement rates (75–95%) of test larvae were observed in response to natural sediment. Sterilization of natural sediment significantly decreased Settlement of P. cornuta (25–55%) while combustion of sediment significantly decreased the Settlement rate in both species (5–50%). Differences in Settlement responses to sediments treated by sterilization or combustion most likely resulted from a variety of factors such as modified sediment fabric, grain size distribution and quantity of adsorbed organic matter. To experimentally address the potential role of microorganisms and microbial metabolites as mediators of Larval Settlement, ashed sediment was inoculated with viable microorganisms obtained from natural sediment. In both polychaete species, this treatment significantly increased Larval Settlement in comparison to the control of ashed sediment indicating that Larval Settlement was at least partially mediated by the presence of microorganisms associated with sediment.
Shelah Mae A. Buen - One of the best experts on this subject based on the ideXlab platform.
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Evaluation of mucus, Navicula, and mixed diatoms as Larval Settlement inducers for the tropical abalone Haliotis asinina
Aquaculture, 2003Co-Authors: Wenresti G. Gallardo, Shelah Mae A. BuenAbstract:Abstract Different biological films reportedly effective in Larval Settlement of other abalone species were tested on the tropical abalone Haliotis asinina to determine the most effective Settlement inducers for the species. Larval attachment was significantly higher on mucus, Navicula , Navicula +mucus, and mixed diatoms+mucus than on mixed diatoms and the blank control. Metamorphosis was significantly higher on Navicula , Navicula +mucus. These results indicate the important contribution of mucus in Larval Settlement and the effectiveness of Navicula as a single species over mixed diatoms in Larval Settlement of the tropical abalone H. asinina .
