Hydroides Elegans Research Articles

Marine Tubeworm Metamorphosis Induced by Arrays of Bacterial Phage Tail–Like Structures

Many benthic marine animal populations are established and maintained by free-swimming larvae that recognize cues from surface-bound bacteria to settle and metamorphose. Larvae of the tubeworm Hydroides elegans, an important biofouling agent, require contact with surface-bound bacteria to undergo metamorphosis; however, the mechanisms that underpin this microbially mediated developmental transition have been enigmatic. Here, we show that a marine bacterium, Pseudoalteromonas luteoviolacea, produces arrays of phage tail-like structures that trigger metamorphosis of H. elegans. These arrays comprise about 100 contractile structures with outward-facing baseplates, linked by tail fibers and a dynamic hexagonal net. Not only do these arrays suggest a novel form of bacterium-animal interaction, they provide an entry point to understanding how marine biofilms can trigger animal development.

污损性管栖多毛类生态特点及研究展望

PDF HTML阅读 XML下载 导出引用 引用提醒 污损性管栖多毛类生态特点及研究展望 DOI: 10.5846/stxb201311022651 作者: 作者单位: 中国科学院南海海洋研究所,中国科学院大学,国防科学技术大学理学院,中国科学院南海海洋研究所,国防科学技术大学理学院 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金(41176102,31100260); 广州市科技计划项目(2013J4300046); 广东省海洋与渔业科技推广专项重点项目(A201101F03) An overview of fouling sedentary polychaetes Author: Affiliation: South China Sea Institute of Oceanology,Chinese Academy of Sciences,,,, Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:污损性管栖多毛类属环节动物门,主要由龙介虫科(Serpulidae)、螺旋虫科(Spirorbidae)、缨鳃虫科(Sabellidae)和蛰龙介科(Terebllidae)4科55种组成,以华美盘管虫(Hydroides elegans)、内刺盘管虫(H. ezoensis)、龙介虫(Serpula vermicularis)和克氏无襟毛虫(Pomatoleios kraussii)等种类为优势种,通常成批的附着在物体表面,严重影响人工设施的安全和性能.污损性管栖多毛类的分布具有明显的地域性和季节性,并与深度有关.今后工作应进一步开展管栖多毛类基础生物学研究,探讨外来种的入侵及影响,丰富和发展生态和分类等方面的研究内容. Abstract:Sedentary polychaetes are conspicuous with numerous species in marine environments. They can also be a major component of fouling communities. As fouling organisms, they can be divided into four families (Serpulidae, Spirorbidae, Sabellidae and Terebllidae) with a total of 55 species identified, of which the dominant species are Hydroides elegans, H. ezoensis, H. diramphus, H. norvegicus, H. operculatus, Pomatoleios kraussii, Serpula vermicularis, Spirobranchus polytrema, S. tetraceros, Ficopomatus enigmaticus and Thelepus cincinnatus.Sedentary polychaetes usually live in tubes, which they themselves secrete. Tubes are either attached to surfaces or to each other forming tangled batches; such tubes are difficult to remove even when the occupying worms have died. Their larvae can settle on various underwater man-made substrata, and post-settlement tube growth may cause serious impairment problems such as adding weight to buoys, decreasing ship speed (more fuel consumption, so increasing CO2 emission), blocking seawater pipelines and aquaculture nets. Fouling sedentary polychaetes are widely distributed in tropical, subtropical and temperate waters. However, they are not homogeneously distributed over the different biogeographical regions. In the Pacific Ocean the common species are Hydroides elegans, H. ezoensis, H. centrospina, H. longistylairs, H. multispinosa, H. prisca, Serpula cf. hartmanae and S. tetratropia. Whereas Ficopomatus uschakovi, Hydroides heterocerus, H. minax and Spirobranchus semperi are only found in the Indian Ocean and Hydroides brachyacanthus, Serpula concharum, Spirobranchus lamarcki and Pseudovermilia occidentalis mainly occur in the Atlantic Ocean.Fouling sedentary polychaetes range from shallow coastal habitats to deep water. However, most previous work is restricted to coastal waters as studies in the deep ocean are rare. Moreover, different species prefer particular substrata. For example Pomatoleios kraussii and Hydroides operculatus tend to settle on the hulls of ships, whereas H. ezoensis and H. diramphus are generally abundant on quay and aquaculture equipment. Understanding their settlement processes is likely to contribute to the development of novel antifouling technology.Sedentary polychaetes are appropriate representative animals to evaluate the impact of environmental factors on marine ecological systems and from the viewpoint of antifouling studies, they are also ideal testing models. Therefore, further work should be focused on the aspects of larval development and settlement mechanisms of the dominant species. Moreover, with the increase in oceanic development and utilization activities, more man-made facilities now occur in deeper and colder waters. Lack of information on fouling sedentary polychaetes in such environment means urgent further studies are now necessary.Due to the limitations of traditional taxonomic methods it is sometimes difficult to identify related polychaete species effectively. Modern genetic technology should provide the answers. Furthermore, some sedentary polychaetes can be easily transported by ship to new environments. As such alien invasive species they can cause serious ecological problems. Based on the reasons mentioned above future work should address the issues of taxonomy and invasive species. 参考文献 相似文献 引证文献

Development of a feeding trochophore in the polychaete Hydroides elegans.

Hydroides elegans is an indirectly developing polychaete with equal spiral cleavage, gastrulation by invagination, and a feeding trochophore. Expression of several transcription factors and differentiation genes has been characterized. Comparative analysis reveals evolutionarily conserved roles. For example, the synexpression of transcription factors FoxA and Brachyury suggests homology of primary and secondary gut openings in protostomes and deuterostomes, and the expression of Sall suggests similar regulatory controls in the posterior growth zone of bilaterians. Differences in gene expression suggest regulatory differences control gastrulation by invagination in polychaetes with a feeding trochophore and gastrulation by epiboly in polychaetes without a feeding trochophore. Association of histone variant H2A.Z with transcriptional potency and its expression suggest a developmental role during both embryogenesis and the larva-to-adult transformation. Methods are being developed for experimental exploration of the gene regulatory networks involved in trochophore development in Hydroides. It is unknown if polychaete feeding trochophores evolved from a larval stage already present in the life cycle of the last common ancestor of protostomes and deuterostomes. Previous evolutionary scenarios about larval origins overemphasize the discontinuity between larval and adult development and require the early evolution of undifferentiated and transcriptionally potent "set aside" cells. Indirect development may proceed by developmental remodeling of differentiated cells and could have evolved after gradual transformation of juveniles into larvae; undifferentiated and transcriptionally potent cells would have evolved secondarily. Comprehensive characterization of gene regulatory networks for feeding trochophore development may help resolve these major evolutionary questions.

Proteomic response of marine invertebrate larvae to ocean acidification and hypoxia during metamorphosis and calcification

Calcifying marine invertebrates with complex life cycles are particularly at risk to climate changes as they undergo an abrupt ontogenetic shift during larval metamorphosis. Although our understanding of the larval response to climate changes is rapidly advancing, the proteome plasticity involved in a compensatory response to climate change is still unknown. In this study, we investigated the proteomic response of metamorphosing larvae of the tubeworm Hydroides elegans, challenged with two climate change stressors, ocean acidification (OA; pH 7.6) and hypoxia (HYP; 2.8 mg O2 l(-1)), and with both combined. Using a two-dimensional gel electrophoresis (2-DE)-based approach coupled with mass spectrometry, we found that climate change stressors did not affect metamorphosis except under OA, but altered the larval proteome and phosphorylation status. Metabolism and various stress and calcification-related proteins were downregulated in response to OA. In OA and HYP combined, HYP restored the expression of the calcification-related proteins to the control levels. We speculate that mild HYP stress could compensate for the negative effects of OA. This study also discusses the potential functions of selected proteins that might play important roles in larval acclimation and adaption to climate change.

Temperature Dependent Effects of Elevated CO2 on Shell Composition and Mechanical Properties of Hydroides elegans: Insights from a Multiple Stressor Experiment

The majority of marine benthic invertebrates protect themselves from predators by producing calcareous tubes or shells that have remarkable mechanical strength. An elevation of CO2 or a decrease in pH in the environment can reduce intracellular pH at the site of calcification and thus interfere with animal’s ability to accrete CaCO3. In nature, decreased pH in combination with stressors associated with climate change may result in the animal producing severely damaged and mechanically weak tubes. This study investigated how the interaction of environmental drivers affects production of calcareous tubes by the serpulid tubeworm, Hydroides elegans. In a factorial manipulative experiment, we analyzed the effects of pH (8.1 and 7.8), salinity (34 and 27‰), and temperature (23°C and 29°C) on the biomineral composition, ultrastructure and mechanical properties of the tubes. At an elevated temperature of 29°C, the tube calcite/aragonite ratio and Mg/Ca ratio were both increased, the Sr/Ca ratio was decreased, and the amorphous CaCO3 content was reduced. Notably, at elevated temperature with decreased pH and reduced salinity, the constructed tubes had a more compact ultrastructure with enhanced hardness and elasticity compared to decreased pH at ambient temperature. Thus, elevated temperature rescued the decreased pH-induced tube impairments. This indicates that tubeworms are likely to thrive in early subtropical summer climate. In the context of climate change, tubeworms could be resilient to the projected near-future decreased pH or salinity as long as surface seawater temperature rise at least by 4°C.

Hypoxia induces abnormal larval development and affects biofilm–larval interaction in the serpulid polychaete Hydroides elegans

Hydroides elegans, a worldwide fouling polychaete, can spawn throughout the year, but its recruitment drops during summer when hypoxia prevails. Here, the influence of hypoxia on larval development and settlement of H. elegans was investigated. Results showed that larval development was compromised at 1mg O2 l−1 with a lower proportion of competent larvae and a higher proportion of malformed larvae, probably due to reduction in clearance rate. Regarding larval settlement, although most of the larvae were reluctant to settle at 1mg O2 l−1, regardless of the biofilm nature, they settled quickly within 24h in response to the resumption of dissolved oxygen. Furthermore, only about 5% of the larvae settled on the biofilms developed under hypoxia, regardless of dissolved oxygen levels of the seawater. The delayed larval development and potential alteration of biofilm nature owing to hypoxia explained why the recruitment of H. elegans declines during summer.

Effect of parental hypoxic exposure on embryonic development of the offspring of two serpulid polychaetes: Implication for transgenerational epigenetic effect

Sperm production and motility, fecundity, and egg size, complexity and viability of serpulid polychaetes Hydroides elegans and Hydroides diramphus after 2-week treatment to hypoxia (2mg O2l−1) was compared with those under normoxia (6mg O2l−1). Despite reduced fecundity, the effect of parental hypoxic exposure on gamete quality was not discernible for both species. However, regardless of their subsequent dissolved oxygen environment, eggs spawned by H. elegans after hypoxic exposure were found to have lower fertilization success, slower embryonic development and a significantly higher yield of malformed embryos than those with a parental normoxic treatment. In contrast, neither fertilization success nor rate of embryonic development was affected for H. diramphus. The results implied that hypoxia was a potential stress reducing the recruitment of H. elegans through non-adaptive epigenetic effect, whereas H. diramphus was a more tolerant species to survive hypoxic events.

An organizing activity is required for head patterning and cell fate specification in the polychaete annelid Capitella teleta: New insights into cell–cell signaling in Lophotrochozoa

Many lophotrochozoans (i.e., molluscs, annelids, nemerteans, and polyclad flatworms) display a well-conserved early developmental program called spiral cleavage that contrasts with the high diversity of adult body forms present in this group. Due to this stereotypical development, each cell can be uniquely identified and its lineage history known following intracellular injection of lineage tracers. Cell deletion experiments performed mainly in molluscs have demonstrated that one or two cells associated with the endomesodermal lineage represent an embryonic organizer of subsequent development and are causally involved in cell fate and body patterning. Utilizing the published fate map of the spiral-cleaving annelid Capitella teleta, we used infrared laser cell deletions to dissect the role of individual cells on the patterning of the larval body. Thirteen uniquely identifiable individual blastomeres and two double cell combination deletions were studied to assess larval phenotypes by scoring multiple morphological structures and cell type-specific molecular markers differentially expressed along the antero-posterior and dorso-ventral axes. Surprisingly, our results show that in C. teleta, the cellular identity of the “organizing cell” and the timing of the organizing activity are different from that of other spiralians. In C. teleta, the ectodermal primary somatoblast, 2d, is the key cell responsible for organizing activity during early embryonic development, and is necessary for bilateral symmetry and dorso-ventral axis organization of the head as well as neural, foregut and mesoderm tissue formation. Furthermore, we show that the ERK/MAPK signaling pathway does not appear to be involved in organizing activity in C. teleta. This contrasts with data from molluscs and the molecular mechanism suggested for another polychaete, Hydroides elegans, highlighting likely molecular level variation among spiralian embryos. These results reinforce the idea that an embryonic organizing activity is present across spiralians. Our data also emphasize the developmental variation within lophotrochozoans, and may ultimately provide insight into the role of developmental processes in the evolution of diverse body forms in metazoans.

Physiological and behavioural responses of different life stages of a serpulid polychaete to hypoxia

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 477:135-145 (2013) - DOI: https://doi.org/10.3354/meps10175 Physiological and behavioural responses of different life stages of a serpulid polychaete to hypoxia Y. S. Leung1, P. K. S. Shin1, J. W. Qiu2, P. O. Ang3, J. M. Y. Chiu4, V. Thiyagarajan4, S. G. Cheung1,* 1Department of Biology and Chemistry, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong, SAR 2Department of Biology, Hong Kong Baptist University, Hong Kong, SAR 3School of Life Sciences, Chinese University of Hong Kong, New Territories, Hong Kong, SAR 4School of Biological Sciences, The University of Hong Kong, Pokfulam, Hong Kong, SAR *Corresponding author. Email: bhsgche@cityu.edu.hk ABSTRACT: Hypoxia has become a major threat to coastal marine ecosystems worldwide. Among various groups of marine invertebrates, sessile ones are more susceptible to hypoxia since they cannot move away from hypoxic waters. The serpulid polychaete Hydroides elegans Haswell, 1883 is a fast-proliferating, dominant, sessile-fouling species in the tropical Pacific, which includes Hong Kong. We studied the effects of hypoxia on the fertilization success, embryogenesis and physiological and behavioural responses in both larval and adult stages of H. elegans. Results showed that fertilization success was reduced and embryogenesis was retarded at a dissolved oxygen (DO) level of 2 mg O2 l-1. At this DO level, the swimming velocity of the 2 d old larvae significantly increased, which may serve as an escape response. H. elegans showed a very high tolerance to hypoxia in both larval and adult stages, as indicated by the 24 and 48 h lethal DO concentation (LC50). However, the respiration rate and clearance rate of adult H. elegans were significantly reduced at 2 mg O2 l-1. Partial recovery was observed 2 d after normoxia was resumed. Previous studies have demonstrated that adult H. elegans suffer from high mortality and that there are no new recruits in summer when the temperature is high and DO concentration low. The results are interpreted as the effect of low salinity. Our study has strengthened the notion that low salinity contributes to adult mortality in summer; however, the lack of summer recruitment is possibly a result of the combined effect of low salinity and hypoxia. KEY WORDS: Hypoxia · Hydroides elegans · LC50 · Embryogenesis · Respiration rate · Clearance rate Full text in pdf format PreviousNextCite this article as: Leung YS, Shin PKS, Qiu JW, Ang PO, Chiu JMY, Thiyagarajan V, Cheung SG (2013) Physiological and behavioural responses of different life stages of a serpulid polychaete to hypoxia. Mar Ecol Prog Ser 477:135-145. https://doi.org/10.3354/meps10175 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 477. Online publication date: March 12, 2013 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2013 Inter-Research.

Brachyury, Tbx2/3 and sall expression during embryogenesis of the indirectly developing polychaete Hydroides elegans

Expression of the transcription factor genes brachyury, Tbx2/3 and sall is characterized in detail for the first time in an indirectly developing spiralian with a feeding trochophore. In Hydroides elegans, gut formation proceeds by invagination during embryogenesis and is followed by feeding-dependent posterior growth during larval stages. Posterior growth gives rise to the reproductive and segmented portion of the adult and derives primarily from multipotent dorsal blastomeres. Dorsal fate becomes morphologically evident at the 60-cell stage during spiral cleavage, although the timing of dorsal specification remains uncertain. Expression of brachyury anticipates the morphogenetic events associated with both gastrulation by invagination in the endoderm and ventral midline convergent extension in the ectoderm. The absence of brachyury expression in endoderm precursors previously reported in annelids that do not have feeding larvae suggests evolutionarily conserved roles associated with morphogenesis rather than endoderm specification. Synexpression of brachyury and FoxA in the blastopore of eumetazoans as well as in the secondarily formed anus of some protostomes and the mouth of deuterostomes suggests shared regulatory circuits during the formation of both oral and anal openings in protostomes and deuterostomes. Expression of sall during gastrulation, in the protonephridium, and in posterior growth zone precursors, also suggests evolutionarily conserved roles. The dorsal sides of the Hydroides and sea urchin embryos express Tbx2/3 in all three germ layer precursors, suggesting evolutionarily conserved dorsal regionalization functions. The results suggest specific gene usage during tubular gut formation, endoderm specification, dorsoventral specification and anteroposterior body elongation in the context of development by feeding larva.

Decreased pH does not alter metamorphosis but compromises juvenile calcification of the tube worm Hydroides elegans

Using CO2 perturbation experiments, we examined the pre- and post-settlement growth responses of a dominant biofouling tubeworm (Hydroides elegans) to a range of pH. In three different experiments, embryos were reared to, or past, metamorphosis in seawater equilibrated to CO2 values of about 480 (control), 980, 1,480, and 2,300 μatm resulting in pH values of around 8.1 (control), 7.9, 7.7, and 7.5, respectively. These three decreased pH conditions did not affect either embryo or larval development, but both larval calcification at the time of metamorphosis and early juvenile growth were adversely affected. During the 24-h settlement assay experiment, half of the metamorphosed larvae were unable to calcify tubes at pH 7.9 while almost no tubes were calcified at pH 7.7. Decreased ability to calcify at decreased pH may indicate that these calcifying tubeworms may be one of the highly threatened species in the future ocean.

CO2-Driven Ocean Acidification Alters and Weakens Integrity of the Calcareous Tubes Produced by the Serpulid Tubeworm, Hydroides elegans

As a consequence of anthropogenic CO2-driven ocean acidification (OA), coastal waters are becoming increasingly challenging for calcifiers due to reductions in saturation states of calcium carbonate (CaCO3) minerals. The response of calcification rate is one of the most frequently investigated symptoms of OA. However, OA may also result in poor quality calcareous products through impaired calcification processes despite there being no observed change in calcification rate. The mineralogy and ultrastructure of the calcareous products under OA conditions may be altered, resulting in changes to the mechanical properties of calcified structures. Here, the warm water biofouling tubeworm, Hydroides elegans, was reared from larva to early juvenile stage at the aragonite saturation state (ΩA) for the current pCO2 level (ambient) and those predicted for the years 2050, 2100 and 2300. Composition, ultrastructure and mechanical strength of the calcareous tubes produced by those early juvenile tubeworms were examined using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and nanoindentation. Juvenile tubes were composed primarily of the highly soluble CaCO3 mineral form, aragonite. Tubes produced in seawater with aragonite saturation states near or below one had significantly higher proportions of the crystalline precursor, amorphous calcium carbonate (ACC) and the calcite/aragonite ratio dramatically increased. These alterations in tube mineralogy resulted in a holistic deterioration of the tube hardness and elasticity. Thus, in conditions where ΩA is near or below one, the aragonite-producing juvenile tubeworms may no longer be able to maintain the integrity of their calcification products, and may result in reduced survivorship due to the weakened tube protection.

Epibiota of the spider crab Schizophrys dahlak (Brachyura: Majidae) from the Suez Canal with special reference to epizoic diatoms

This study aims to describe the epibiota of the spider crab, Schizophrys dahlak with special reference to epizoic diatoms. Specimens were collected from the Suez Canal between autumn 2008 and summer 2009. Macro-epibionts consisted of the tube worm Hydroides elegans , the barnacles Balanus amphitrite and B. eburneus , the bivalve Brachidontes variabilis and the urochordate Styela plicata . Total coverage of macro-epibionts was greater on females' carapaces than those of males with apparent seasonal variations. The highest coverage was noticed in spring and winter for both males and females. Sixty-five diatoms taxa were recorded as epibionts belonging to 25 genera. The maximal total averages of cell count were observed during summer and spring with the highest average of 10.9 and 4.4 × 10 3 cells dm −2 for males and females, respectively. A single diatom taxon, Fragilaria intermedia , comprising 73.5% of all epizoic diatoms, was the most dominant species during spring, whereas Amphora coffeaeformis and Cocconeis placentula were the dominants during summer. The masking behaviour of S. dahlak was discussed in terms of the significant role of epizoic diatoms.

Characterization and expression of calmodulin gene during larval settlement and metamorphosis of the polychaete Hydroides elegans

The polychaete Hydroides elegans (Serpulidae, Lophotrochozoa) is a problematic marine fouling organism in most tropical and subtropical coastal environment. Competent larvae of H. elegans undergo the transition from the swimming larval stage to the sessile juvenile stage with substantial morphological, physiological, and behavior changes. This transition is often referred to as larval settlement and metamorphosis. In this study, we examined the possible involvement of calmodulin (CaM) - a multifunctional calcium metabolism regulator, in the larval settlement and metamorphosis of H. elegans. A full-length CaM cDNA was successfully cloned from H. elegans (He-CaM) and it contained an open reading frame of 450 bp, encoding 149 amino acid residues. It was highly expressed in 12h post-metamorphic juveniles, and remained high in adults. In situ hybridization conducted in competent larvae and juveniles revealed that He-CaM gene was continuously expressed in the putative growth zones, branchial rudiments, and collar region, suggesting that He-CaM might be involved in tissue differentiation and development. Our subsequent bioassay revealed that the CaM inhibitor W7 could effectively inhibit larval settlement and metamorphosis, and cause some morphological defects of unsettled larvae. In conclusion, our results revealed that CaM has important functions in the larval settlement and metamorphosis of H. elegans.

Recruitment in the sea: bacterial genes required for inducing larval settlement in a polychaete worm

Metamorphically competent larvae of the marine tubeworm Hydroides elegans can be induced to metamorphose by biofilms of the bacterium Pseudoalteromonas luteoviolacea strain HI1. Mutational analysis was used to identify four genes that are necessary for metamorphic induction and encode functions that may be related to cell adhesion and bacterial secretion systems. No major differences in biofilm characteristics, such as biofilm cell density, thickness, biomass and EPS biomass, were seen between biofilms composed of P. luteoviolacea (HI1) and mutants lacking one of the four genes. The analysis indicates that factors other than those relating to physical characteristics of biofilms are critical to the inductive capacity of P. luteoviolacea (HI1), and that essential inductive molecular components are missing in the non-inductive deletion-mutant strains.

A biomonitor as a measure of an ecologically-significant fraction of metals in an industrialized harbour

Biomonitors are commonly used to assess levels of bioavailable contaminants in the environment, however the relationships between biomonitor tissue concentrations and ecological effects are rarely assessed. The present study investigated metal contamination within a highly industrialised harbour and ecological effects on sessile invertebrates. The native oyster Saccostrea glomerata was deployed as a biomonitor across twenty-six sites to test for correlations between metal levels in their tissues and the recruitment of hard-substrate invertebrates. Concentrations of lead and copper in oyster tissues were negatively correlated with densities of the dominant barnacle, Amphibalanus variegatus, and positively correlated with densities of the dominant polychaete, Hydroides elegans, and the two native encrusting bryozoans Celloporaria nodulosa and Arachnopusia unicornis. Results suggest that highly localised events drive contaminant availability and that these events pose a significant risk to fauna. Biomonitoring studies may be enhanced by running concurrent ecological surveys.

Influence of surface characteristics on biofouling formed on polymers exposed to coastal sea waters of India

Biofouling on six different (silicone rubber, polydimethylsiloxane, polypropylene, high density polyethylene, polyvinylchloride, and polycarbonate) substrata with varying surface energy (18–40 mN/m) and surface roughness ( R a 45–175 μm) was studied in the Eastern coastal waters of India over a short period of time (3 days). The results showed that the substrata surface energy (SE) followed by the surface roughness ( R a) had profound effect on attachment of fouling organisms. After one day of immersion, viable count of bacteria in the biofilm was positively correlated with surface energy ( r = 0.69, p < 0.05) and not with surface roughness ( r = −0.02) of the substratum. Whereas, Pseudomonas count was inversely correlated with surface energy ( r = −0.66, p < 0.05) and surface roughness ( r = −0.52, p < 0.05). The attachment of macrofouler and the surface characteristics were also well correlated with SE 0.48 and with roughness 0.62, p < 0.05. A positive correlation was observed amongst the various biofouling constituents such as bacteria, ATP, carbohydrates and organic matter on almost all the substrata. However after the first day, the surface characteristics of the substratum became less important and the conditioning film that was formed on the substrata appeared to directly influence further fouling on the surfaces, as evidenced by poor correlation between surface energy and macrofouler attachment ( r = −0.11). The observation of high numbers of Hydroides elegans on PVC could be solely due to the influence of surface roughness ( r = 0.62). Though there is no marked difference in the ‘primary film’, and the composition of the biofilm, the amount of attached macrofouler is minimal on silicone rubber and polydimethylsiloxane on subsequent days of immersion, which reveals the foul release quality of these substrata probably due to their flexible nature.

Correlation between pigmentation and larval settlement deterrence by Pseudoalteromonas sp. sf57

The red-pigmented marine bacterium Pseudoalteromonas sp. sf57 forms a biofilm that deters larval settlement of the tube-building polychaete Hydroides elegans. To investigate the correlation between pigmentation and larval settlement deterrence, mutants of sf57 with deficient or altered pigmentation were generated by transposon mutagenesis. Five groups of pigmented mutants were obtained, viz. white, yellow, pink, dark red, and white-to-red. The white mutant WM1, which exhibited a substantial increase in bacterial density in the biofilm, became inductive to larval settlement. The other mutants that showed a lesser increase in bacterial density in their biofilms either retained their deterrence or induced higher larval settlement rates, but did not become inductive strains. Analysis of the disrupted genes in these mutants suggests that the type II secretion pathway, the LysR transcriptional regulator, NAD(P)-binding proteins, exonuclease, pyruvate metabolism, flagella assembly, and cell membrane processes may play a role in the regulation of pigmentation in sf57.

Biofilms and Marine Invertebrate Larvae: What Bacteria Produce That Larvae Use to Choose Settlement Sites

Communities of microorganisms form thin coats across solid surfaces in the sea. Larvae of many marine invertebrates use biofilm components as cues to appropriate settlement sites. Research on the tube-dwelling polychaete worm Hydroides elegans, a globally common member of biofouling communities, is described to exemplify approaches to understanding biofilm bacteria as a source of settlement cues and larvae as bearers of receptors for bacterial cues. The association of species of the bacterial genus Pseudoalteromonas with larval settlement in many phyla is described, and the question of whether cues are soluble or surface-bound is reviewed, concluding that most evidence points to surface-bound cues. Seemingly contradictory data for stimulation of barnacle settlement are discussed; possibly both explanations are true. Paleontological evidence reveals a relationship between metazoans and biofilms very early in metazoan evolution, and thus the receptors for bacterial cues of invertebrate larvae are very old and possibly unique. Finally, despite more than 60 years of intense investigation, we still know very little about either the bacterial ligands that stimulate larval settlement or the cellular basis of their detection by larvae.

清水港に流人する巴川惑潮域に設置した実験板に付着した海洋付着生物の分布について

The distributions of the species of sessile organisms settling on test plates immersed in the lower reaches of the Tomoe River in Shizuoka, Japan, was investigated during late summer in 2002. Sessile organisms settled actively from the mouth of the river to sites about 2 km upstream, while the settlement of fewer species was confirmed farther upstream at about 5 km from the mouth. The main species found settling on the test plates were the barnacles Fistulobalanus albicostatus and Amphibalanus amphitrite, and the polychaetes Hydroides elegans and Dexiospira foraminosa. Fistulobalanus albicostatus and H. elegans settled from the mouth all the way to 5 km upstream while D. foraminosa settled at only two sites about 2 km from the mouth. Cluster analysis conducted according to the dissimilarity of species composition among the 60 test plates classified the sessile organisms into six sub-communities. Near the mouth of the river, the communities were distributed mainly in the middle layer of the water column, while they were distributed among all layers at the sites 2 km upstream. Farther upstream, the communities were distributed in the bottom layers within the salt wedge and became sparse at the uppermost sites. The distributions of sessile organism species were strongly correlated with salinity in the lower reaches of this river.