Adhesion Of Zoospores Research Articles

Research progress of anti-fouling materials for fishing and its application in fisheries

Marine biological fouling is formed by the adsorption, growth and reproduction of marine microorganisms, plants and animals on marine facilities (such as ship hulls, buoys, bridge piers, cages and nets, etc.), which is harmful to aquaculture. Marine fouling organisms such as barnacles (<italic>Balanus</italic>), mussels (<italic>Mytilus edulis</italic>) and algae are prone to adsorb on fishing nets. This can cause poor water exchange between the inside and outside of the fishing net, and substantial increase in water resistance of the net. The existing anti-fouling methods include manual removal method, mechanical removal method, biological anti-fouling method, metal mesh anti-fouling method and anti-fouling coating method. Due to the variety of marine fouling organisms, different sea conditions in aquaculture and the safety for fish, the anti-fouling technology for fishing nets is very difficult. Therefore, it is very important to develop green, long-lasting and economical anti-fouling materials for fishing. This article starts with the introduction of the classification of anti-fouling materials, then three types of anti-fouling materials for fishing, including anti-fouling coatings, anti-fouling functional metal and composite anti-fouling materials are introduced. And advantages and disadvantages of the application of three anti-fouling materials in fishery are revealed. These current applications can provide references for the development of high-performance anti-fouling materials for fishing. Moreover, the main anti-fouling mechanisms are provided: 1) self polishing refers to the automatic polishing of the failed surface layer by washing with seawater; 2) the structure of microphase separation, which has excellent resistance to lipopolysaccharide, protein and zoospore adhesion; 3) the low surface energy and large water contact angle of the surface make it difficult for fouling organisms to attach; 4) slow release of anti-fouling agents; 5) contact death caused by the adsorption of cations. The anti-fouling technology of fishing nets is of great significance for aquaculture industry. In order to meet the needs of green development strategy for aquaculture, the development of green, environment-friendly, long-term, economical anti-fouling materials will be one of the hot spots of future fishery science.

Segmental Enteritis Associated with Pythium insidiosum Infection in a Horse

Background: Pythiosis is an infectious disease caused by the oomycete Pythium insidiosum, with higher occurrence in wetlands and hot climate regions. This microorganism develops its cycle in aquatic plants, and most cases happen because of the contact of animals or people with water containing the motile zoospores (infectious form). Horses are the principal species affected and develop principally cutaneous and subcutaneous lesions, but the gastrointestinal tract is seldom affected. Humans develop various forms of pythiosis, such as a vascular form. The objectives of the current study are to describe an unusual case of intestinal pythiosis, its clinical signs, aspects of pathogenesis, and diagnosis.Case: A 13-year-old Crioula mare, from Santa Maria, RS, Brazil, presented with reduced food and water intake, apathy, restlessness, rolling, nasal reflux, firm abdomen upon palpation, and tachypnea during 2 days. The horses of this farm were fed native pasture and horse feed, and they had access to a nearby pond. Two days following the start of the clinical signs, the horse died and was necropsied on the farm. During necropsy, there was around 400 mL of reddish effusion in the abdominal cavity (modified transudate). A 15 cm segment of jejunum was firm upon palpation and had a severe transmural thickening. The wall of the affected area was up to 3 cm in thickness and firm, with small yellowish and irregular masses that stood out and looked friable, interpreted as kunkers. Microscopically, the yellowish masses (kunkers) were characterized by dense accumulations of intact and degenerate eosinophils (eosinophilic necrosis). Within these kunkers, and also on their periphery, there were multiple negatively stained hyphal profiles. Hyphae were also seen on the wall of small arteries inside the kunkers. These hyphae had nearly parallel walls and were occasionally septate, with a diameter of about 10 μm. The hyphae stained black with Grocott’s methenamine silver stain (GMS) and were positive on immunohistochemistry (IHC) using specific anti-P. insidiosum polyclonal antibody.Discussion: Colic is the principal clinical presentation in horses suffering from gastrointestinal tract disorders. In spite of the presence of colic in this horse, intestinal pythiosis was not clinically suspected in this case, principally because of its rare occurrence in horses. Even though it is persistent to observe horses ingesting water with suspected contamination by P. insidiosum, the cutaneous form of pythiosis is a lot more common than the intestinal form. This is the only case of intestinal pythiosis in a horse in 52 years of routine diagnosis in our laboratory. It is suspected that this horse got infected by drinking contaminated water from the nearby pond and microlesions in the intestinal mucosa due to plant material or some unknown pathogen may have favored zoospore adhesion, encysting and starting the colonization of the tissue by emitting a germ tube. A macroscopic observation of kunkers in the intestine is rare, but when observed it is highly indicative of pythiosis. The immunohistochemistry technique using anti-P. insidiosum antibody, in accordance with the literature, validates the diagnosis of pythiosis. In this case, the presence of hyphae in the blood vessel wall inside the kunkers propose that this finding may be involved in the spread of the lesion but needs more detailed studies.

Characterization of Zoospore Type IV Pili in Actinoplanes missouriensis.

The rare actinomycete Actinoplanes missouriensis produces terminal sporangia containing a few hundred flagellated spores. After release from the sporangia, the spores swim rapidly in aquatic environments as zoospores. The zoospores stop swimming and begin to germinate in niches for vegetative growth. Here, we report the characterization and functional analysis of zoospore type IV pili in A. missouriensis The pilus gene (pil) cluster, consisting of three apparently σFliA-dependent transcriptional units, is activated during sporangium formation similarly to the flagellar gene cluster, indicating that the zoospore has not only flagella but also pili. With a new method in which zoospores were fixed with glutaraldehyde to prevent pilus retraction, zoospore pili were observed relatively easily using transmission electron microscopy, showing 6 ± 3 pili per zoospore (n = 37 piliated zoospores) and a length of 0.62 ± 0.35 μm (n = 206), via observation of fliC-deleted, nonflagellated zoospores. No pili were observed in the zoospores of a prepilin-encoding pilA deletion (ΔpilA) mutant. In addition, the deletion of pilT, which encodes an ATPase predicted to be involved in pilus retraction, substantially reduced the frequency of pilus retraction. Several adhesion experiments using wild-type and ΔpilA zoospores indicated that the zoospore pili are required for the sufficient adhesion of zoospores to hydrophobic solid surfaces. Many zoospore-forming rare actinomycetes conserve the pil cluster, which indicates that the zoospore pili yield an evolutionary benefit in the adhesion of zoospores to hydrophobic materials as footholds for germination in their mycelial growth.IMPORTANCE Bacterial zoospores are interesting cells in that their physiological state changes dynamically: they are dormant in sporangia, show temporary mobility after awakening, and finally stop swimming to germinate in niches for vegetative growth. However, the cellular biology of a zoospore remains largely unknown. This study describes unprecedented zoospore type IV pili in the rare actinomycete Actinoplanes missouriensis Similar to the case for the usual bacterial type IV pili, zoospore pili appeared to be retractable. Our findings that the zoospore pili have a functional role in the adhesion of zoospores to hydrophobic solid surfaces and that the zoospores use both pili and flagella properly according to their different purposes provide an important insight into the cellular biology of the zoospore.

Effects of sediment influx on the settlement and survival of canopy-forming macrophytes.

Kelp forests on coastal rocky shores are negatively impacted by sudden sediment loads that can occur with storms and floods. Using laboratory experiments, we studied the effects of sediment deposition on the survival of the large brown alga Eisenia bicyclis juveniles (zoospores and gametophytes) to quantify the potential impacts of particulate matter on kelp forests. The zoospore adhesion rate and the gametophyte survival and growth rates all declined markedly with increasing sediment load, particularly with smaller particle diameter. Using experimental results, we derived an equation to calculate the rate of initial kelp depletion with sediment load based on the quantity and size distribution of sediment particles. The equation enabled the estimation of E. bicyclis depletion rates in the field by measurement of particle quantity and diameter distribution of sediments on the reef substrate.

The effects of nitric oxide in settlement and adhesion of zoospores of the green alga Ulva

Previous studies have shown that elevated nitric oxide (NO) reduces adhesion in diatom, bacterial and animal cells. This article reports experiments designed to investigate whether elevated NO reduces the adhesion of zoospores of the green alga Ulva, an important fouling species. Surface-normalised values of NO were measured using the fluorescent indicator DAF-FM DA and parallel hydrodynamic measurements of adhesion strength were made. Elevated levels of NO caused by the addition of the exogenous NO donor SNAP reduced spore settlement by 20% and resulted in lower adhesion strength. Addition of the NO scavenger cPTIO abolished the effects of SNAP on adhesion. The strength of attachment and NO production by spores in response to four coatings (Silastic® T2; Intersleek® 700; Intersleek® 900 and polyurethane) shows that reduced adhesion is correlated with an increase in NO production. It is proposed that in spores of Ulva, NO is used as an intracellular signalling molecule to detect how conducive a surface is for settlement and adhesion. The effect of NO on the adhesion of a range of organisms suggests that NO-releasing coatings could have the potential to control fouling.

Membrane recycling and calcium dynamics during settlement and adhesion of zoospores of the green alga Ulva linza

Recruitment of individuals of the marine alga Ulva linza on to a suitable habitat involves the settlement of motile zoospores on to a substratum during which a preformed adhesive is secreted by vesicular exocytosis. The fluorescent styryl dye FM 1-43 and fluorescent Ca(2+) indicators were used to follow membrane cycling and changes in cytosolic Ca(2+) ([Ca(2+)](cyt)) associated with settlement. When swimming zoospores were exposed continuously to FM 1-43, the plasma membrane was preferentially labelled. During settlement, FM 1-43-labelled plasma membrane was rapidly internalized reflecting high membrane turnover. The internalized membrane was focused into a discrete region indicating targeting of membrane to an endosome-like compartment. Acetoxymethyl (AM)-ester derivatives were found to be unsuitable for monitoring [Ca(2+)](cyt) because the dyes were rapidly sequestered from the cytoplasm into sub-cellular compartments. [Ca(2+)](cyt) was, however, reliably measured using dextran-conjugated calcium indicators delivered into cells using a biolistic technique. Cells loaded with Oregon Green BAPTA-1 dextran (Invitrogen, Paisley, UK) showed diffuse cytosolic loading and reliably responded to imposed changes in [Ca(2+)](cyt). During settlement, zoospores exhibited both localized and diffuse increases in [Ca(2+)](cyt) implying a role for [Ca(2+)](cyt) in exocytosis of the adhesive.

The Antifouling and Fouling-Release Perfomance of Hyperbranched Fluoropolymer (HBFP)−Poly(ethylene glycol) (PEG) Composite Coatings Evaluated by Adsorption of Biomacromolecules and the Green Fouling Alga Ulva

Cross-linked hyperbranched fluoropolymer (HBFP) and poly(ethylene glycol) (PEG) amphiphilic networks with PEG weight percentages of 14% (HBFP-PEG14), 29% (HBFP-PEG29), 45% (HBFP-PEG45), and 55% (HBFP-PEG55) were prepared on 3-aminopropyl)triethoxysilane (3-APS) functionalized microscope glass slides for marine antifouling and fouling-release applications. The surface-free energies (gamma(s)), polar (gamma(s)(p) and gamma(s)(AB)), and dispersion (gamma(s)(d) and gamma(s)(LW)) components were evaluated using advancing contact angles by two-liquid geometric-mean and three-liquid Lifshitz-van der Waals acid-base approaches. The HBFP coating exhibited a low surface energy of 22 mJ/m(2), while the gamma(s) and gamma(s)(p) of the cross-linked HBFP-PEG coatings increased proportionally with the PEG weight percentages in the networks. The adsorption of bovine serum albumin (BSA), lectin from Codium fragile (CFL), lipopolysaccharides from Escherichia coli (LPSE) and Salmonella minnesota (LPSS) upon glass, APS-glass, HBFP, PEG, and the cross-linked HBFP-PEG network coatings were investigated by fluorescence microscopy. The marine antifouling and fouling-release properties of the cross-linked HBFP-PEG coatings were evaluated by settlement and release assays involving zoospores of green fouling alga Ulva (syn. Enteromorpha; Hayden, H. S.; Blomster, J.; Maggs, C. A.; Silva, P. C.; Stanhope, M. J.; Waaland, J. R. Eur. J. Phycol. 2003, 38, 277). The growth and release of Ulva sporelings were also investigated upon the HBFP-PEG45 coating in comparison to a poly(dimethylsiloxane) elastomer (PDMSE) standard material. Of the heterogeneous cross-linked network coatings, the maximum resistances to protein, lipopolysaccharide, and Ulva zoospore adhesion, as well as the best zoospore and sporeling release properties, were recorded for the HBFP-PEG45 coating. This material also exhibited better performance than did a standard PDMSE coating, suggesting its unique applicability in fouling-resistance applications.

Roughness-dependent Removal of Settled Spores of the Green Alga Ulva (syn. Enteromorpha) Exposed to Hydrodynamic Forces from a Water Jet

Topographic features change the hydrodynamic regime over surfaces subjected to flow. Hydrodynamic microenvironments around topographic structures may have consequences for recruitment and removal of propagules of marine benthic organisms. The settlement and adhesion of zoospores from the green alga Ulva linza (syn. Enteromorpha linza) to defined topographies was investigated. A range of topographic size scales (Rz: 25 – 100 μm) was manufactured from plankton nets, creating patterns with ridges and depressions. The topographic scales span a roughness similar to that of natural substrata and antifouling coatings. Spores were removed from the surfaces by a calibrated water jet. Fewer spores were removed from the smallest topographic structure tested (Rz: 25 μm) compared to both the smooth (Rz: 1) and the roughest (Rz: 100 μm) structures. Zoospores that settled in depressions were less likely to be removed compared to spores on the ridges. The results in terms of the interaction between surface topography and hydrodynamic forces have implications for both natural substrata exposed to wave action and antifouling surfaces on ships' hulls. The possible effects of topography on increasing zoospore adhesion and offering a refuge from hydrodynamic forces are discussed.

Inhibitory Effects of Hydrogels on the Adhesion, Germination, and Development of Zoospores Originating from Laminaria angustata

The inhibition of germination and development of zoospores originating from Laminaria angustata originated on various kinds of hydrogels is studied. The effects of the water content of the gel (the degree of swelling), the electrical nature (neutral, positive charge, negative charge), the charge density, the counterions of hydrogels on the inhibition of zoospore germination and development of gametophytes are phenomenologically investigated. Among the gels investigated, poly(acrylic acid) (PAA) gel showed a dramatic inhibition to germination, and might serve as a novel, environmentally safe inhibitor of zoospore adhesion.

Brefeldin A affects adhesion of zoospores of the green alga Enteromorpha.

Primary adhesion of zoospores of the green macroalga Enteromorpha to substrata involves a massive release of adhesive glycoproteins from Golgi-derived, membrane-bounded vesicles in the anterior region of the spore, followed by rapid curing. This process is sensitive to low concentrations (5-10 microg x ml(-1)) of the secretion-inhibiting antibiotic, brefeldin A (BFA). The proportion of cells that settled in BFA was reduced by approximately 50%, but the effect was fully reversed by washing in seawater to remove the BFA. Ultrastructural observations showed that BFA caused the breakdown of Golgi stacks in the majority of cells examined. When settled cells were subjected to shear stress, a greater proportion of those settled in the presence of BFA were detached, compared with controls, indicating reduced adhesion strength in the presence of the antibiotic. The most likely reason for this is that strong adhesion to substrata either requires the synthesis of extra adhesive materials beyond those present in the swimming spore, or the secretion of an additional component required for adhesive curing. The novel use of atomic force microscopy in force modulation mode demonstrated that the adhesive secreted by most spores in the presence of BFA did not undergo the rapid curing process typical of control spores. However, some variation between zoospores was observed, with some cells showing no ultrastructural changes and normal adhesive curing. These results are discussed in relation to variations observed in the propensity and competence of spores to settle, which may be reflected in differential requirements for de novo synthesis and secretion of materials needed for full adhesion.

Cellular and molecular approaches to understanding primary adhesion in Enteromorpha: an overview

The attachment of motile spores of the green alga Enteromorpha to the substratum is an active process involving an irreversible commitment to adhesion and the secretion of an adhesive. This paper provides an overview of the spore adhesion processes and outlines the results of an experimental approach towards the molecular characterisation of the adhesive, based on the use of monoclonal antibody (mAb) technology. Hybridomas were produced to settled spores displaying secreted adhesive. Candidates producing mAbs to putative adhesive were selected using a range of criteria based on cellular localisation, time of secretion and functional inhibition of adhesion. MAb Ent 6 immunolabelled fibrillar material which was secreted during the early stages of adhesion and low (nM) concentrations of this mAb, or its F(ab)2 fragments, strongly inhibited the attachment of zoospores. A related antibody (Ent 1) also labelled the spore adhesive apparatus, but the antigen appeared to be secreted later during the adhesion process and was predominantly associated with the developing cell wall. Ent 1 also inhibited settlement in spore adhesion assays but the effect was most pronounced at later time points which suggests that this antigen does not have a role in the earliest stages of adhesion. Immunolocalisation showed that both antigens were absent from the cytoplasm or organelles of vegetative tissue but labelled the vegetative cell wall, suggesting a relationship between cell wall components and materials involved in primary adhesion. Both mAbs labelled the Golgi region of settled spores, suggesting continued synthesis of both antigens after adhesion. Both mAbs recognised a 110 kDa N‐linked polydisperse and heterogeneous glycoprotein in extracts of swimming spores under denaturing conditions. In native form the antigens behaved as high molecular weight aggregates (Mr>1.3 × 106). The antigens became progressively insoluble after zoospore attachment. Taken together, the data suggest that the two antibodies recognise closely related, polydisperse, self‐aggregating cell wall glycoproteins in which there is some structural variation to suit alternative roles in primary adhesion and cell wall formation. The two mAbs Ent 1 and Ent 6 partially discriminate between these structural and functional variants. A model for zoospore adhesion is discussed in which adhesion is viewed as an extension of cell wall synthesis, with cross‐links between glycoproteins and other cell wall matrix components providing a strong physical continuum between the cell and the adhesive at the substratum interface.

Effects of concanavalin A on the net formation of zoospores in Hydrodictyon reticulatum (Chlorococcales, Chlorophyceae)

SUMMARY In the green alga Hydrodictyon reticulatum (L.) Lager-heim (Chlorococcales, Chlorophyceae), zoospores are arranged in a regular fashion to form an intricate hexagonal network during the asexual reproductive cycle. Polypeptides that bind concanavalin A (Con A) in zoospores increased in amount during net formation and decreased after the completion of the adhesion between zoospores. Fluorescein isothiocyanate-Con A-binding sites corresponded to the contact sites of zoospores immediately after cessation of the movement. Treatment with 25 μg mL−1 Con A inhibited adhesion of isolated immotile zoospores obtained from parental cells, and Con A-treated zoospores could not form hexagonal nets. Moreover, when isolated immotile zoospores were treated with Con A, the cessation of the zoospore movement was retarded in dose-dependent manner. These results suggest that the Con A-binding sites may participate in the adhesion of zoospores during hexagonal net formation.

Attachment of zoospores of the fouling alga enteromorpha in the presence of zosteric acid

The effect on adhesion of Enteromorpha zoospores of a range of concentrations of zosteric acid (p‐(sulpho‐oxy) cinnamic acid) and two unsulphated phenolic acid analogues viz. p‐coumaric acid and trans‐cinnamic acid, was tested. At concentrations up to 0.25 mM, zosteric acid inhibited zoospore adhesion by up to approximately 50% whilst there were no significant differences between the number of adhered zoospores in the presence of p‐coumaric acid and cinnamic acid. None of the test compounds affected the viability of adhered zoospores (measured in terms of germination) at concentrations below 0.5 mM. However, viability decreased in the presence of all the test compounds at concentrations above 0.5 mM. The basis of the non‐toxic inhibition of zoospore adhesion by zosteric acid is discussed.

Enhanced adhesion and chemoattraction of zoospores of the fouling alga enteromorpha to some foul‐release silicone elastomers

Significantly higher numbers of zoospores of the fouling, green alga Enteromorpha adhered to silicone elastomers cured by dibutyltin dilaurate (DBTDL) than to identical polymers cured by dibutyltin diacetate (DBTDA). Enhanced zoospore adhesion was shown to be due to the presence of DBTDL and the effect was concentration‐dependent. Further experiments revealed that enhanced zoospore adhesion also occurred to glass coverslips coated with lauric acid (C12) and other saturated fatty acids. The possibility that fatty acids may act as chemical cues (chemoattractants), guiding motile zoospores to the substratum for settlement in the natural environment is discussed. Settlement of other fouling organisms to DBTDL‐cured silicone elastomers is currently being investigated.

海水中懸濁粒子の沈降・堆積がワカメ遊走子の着生とその生長に及ぼす阻害作用

Effects of suspended and accumulated kaolinite particles on the adhesion and the development of Undaria pinnatifida zoospores on the substratum were investigated under the following three types of condition; Case-1: suspended particles together with zoospores, Case-2: zoospores released after accumulation of particles on the substratum, and Case-3 : accumulated particles on zoospores adhered on the substratum.Case-2 was the most effective inhibition for the adhesion of zoospores, and 50% of effective concentration of particles (EC50) was 29 μg·cm-2. It was difficult for gametophytes to develop to sporophytes in Case-3. Furthermore, in comparing Undaria zoospores with Porphyra conchospores, the zoospores showed higher tolerance to suspended particles.

PRIMARY ADHESION OF ENTEROMORPHA (CHLOROPHYTA, ULVALES) PROPAGULES: QUANTITATIVE SETTLEMENT STUDIES AND VIDEO MICROSCOPY1

ABSTRACTQuantitative methods and associated kinetic analyses have been used for the first time to study detailed aspects of the settlement and adhesion of various types of Enteromorpha popagule. Time course experiments showed that quadri and biflagellate zoospores and zygotes adhered rapidly, but a proportion within any one population appeared to be incompetent at adhering to the substratum. Kinetic (Scatchard) analysis of adhesion experiments performed at a range of zoospore concentrations revealed density‐dependent effects not previously reported, with positive cooperativity at low spore densities and negative cooperativity at high spore densities. High‐resolution video microscopy was used for the first time to reveal details of the various stages in the settlement and adhesion of zoospores and zygotes. Novel observations were made of an initial, temporary phase of attachment via the apical papilla, followed by a permanent phase of commitment, characterized by discharge of adhesive‐containing cytoplasmic vesicles, as the cell contracted against the surface, and adsorption of flagella. The phase of commitment was followed by exploitation of the surface through amoeboid‐like movements at the interface. Gregarious settlement behavior was frequently observed leading to the formation of rafts of cells. The possible mechanisms and significance of density‐dependent spore adhesion are discussed.

Orientated zoospore attachment and cyst germination in Catenaria anguillulae, a facultative endoparasite of nematodes

Zoospores of the nematode-parasitic Catenaria anguillulae (Chytridiomycota) were studied by videomicroscopy in sealed films of water on microscope slides in the presence or absence of freeze-inactivated nematodes ( Panagrellus redivivus ). Zoospores swam for more than 1 h at a mean velocity of 104 μm s -1 , interspersed with repeated phases (1–2 min) of amoeboid crawling on glass or nematode surfaces. They were attracted to and encysted near the mouth, excretory pore, and anus of nematodes, or eventually encysted at random on glass and nematode surfaces. The single posterior flagellum was immobile during amoeboid crawling but resumed rapid beating when the last pseudopodium was being retracted. Zoospores encysted by adhesion of the anterior of an amoeboid cell to a surface; then the cell posterior was raised above the anterior so that the flagellum projected perpendicular to the surface, and the flagellum was retracted by rotation of the cell contents. Cysts germinated within 20–60 min by a narrow germ-tube at the site of adhesion. The germ-tube grew a short distance, then formed an intercalary vesicle into which the cyst contents emptied by expansion of a cyst vacuole. In several cases the germ-tube penetrated a nematode and formed the vesicle inside the host. Rhizoids or assimilative hyphae developed from the vesicle or by growth of the germ-tube tip. An increasing proportion of zoospores that remained motile after 1 h in water films had a globose body in contrast to the normal elongated form. This seemed to be caused by damage during repeated transitions between the amoeboid and swimming phases, because pseudopodia sometimes remained firmly attached to a glass surface. C. anguillulae showed consistent orientation (polarity) of zoospore encystment and cyst germination. This parallels the behaviour of other zoosporic fungi or fungus-like organisms ( Plasmodiophora brassicae, Rozella allomycis, Pythium, Phytophthora and Saprolegnia spp.) suggesting that it is a common feature of zoosporic parasites. Surface-recognition for encystment by C. anguillulae was mediated by the zoospore soma, not the flagellum. In addition, we redefine the early development of C. anguillulae , including flagellar retraction by rotation of cell contents, non-specific adhesion of zoospores and cysts to surfaces, and evacuation of cyst contents into a vesicle from which further growth occurs.

海中の濁りの藻場への影響 ＩＶ 褐藻類カジメ・ワカメ遊走子の着生率と基質傾斜の関係

As one of the studies towards the rehabilitation of the seaweed-bed deteriorated with turbid water, the relationships between the zoospore adhesion of brown algae such as Ecklonia cava and Undaria pinnatifida and the gradients of the seaweed substrate were investigated. The rate of adhesion in the filtered sea water was reduced in inverse proportion to the gradients of the substrate almost in a linear fashion. In the turbid water with suspended particles, however, the deviations in rate of adhered zoospores caused by different gradients of the substrate became smaller as the turbidity increased. Furthermore, when the sediments were deposited very slightly on substrate, the rate of zoospore adhesion decreased suddenly, and the adhesion on a substrate having inclination angle became impossible with sediments only as much as 3mg/cm2, When it was considered that the deposited sediments decreased by the inclination of substrate, the larger the gradient was, the larger was the rate of zoospore adhesion. Under sedimentation of 3mg/cm2, the rate of adhesion with a gradient of 90 degrees showed a maximum value. Also, the adhesion of zoospores relates to the flow of water, and exhibited a maximum value with an approximate flow speed of 3cm/s. Under such circumstances, it was confirmed that the larger its gradient was, the larger was the rate of zoospore adhesion.

Infrared monitoring of the adhesion of Catenaria anguillulae zoospores to solid surfaces

Electron microscopic studies of nematodes infected with the chytridiomycetous fungus Catenaria anguillulae indicated that zoospores of the fungus adhered to the cuticle of nematodes by a layer of extracellular polymers. The chemical composition of the adhesive polymers and their interaction with a solid surface were examined with Fourier transform infrared spectroscopy, using an attenuated total reflectance cell. On-line monitoring of the adhesion of zoospores to a germanium crystal with this technique showed that the adhesive polymers consisted of a protein(s) containing amide I and II bands. The adsorption of these proteins, measured as the increase in the amide II band, had a rapid initial phase of ca. 20 minutes, followed by a slower increase during the course of incubation. Fluorescein isothiocyanate staining of the attached cells at the end of the experiment showed that the adhesion of the zoospores occurred before the formation of the cyst wall.

Culture of seaweedsmonostroma

A species of genus Monostroma cultured and grown in south central Japan along the Pacific coast serves the country as an important source of food. Both in respect of the region where it grows and its ecological characteristics, this is a seaweed that shows striking resemblance with ‘amanori’. The methods of culturing either this species or amanori are also very similar. Most of the species goes into the preparation of a seasoning known as ‘nori tsukudani’. It is also used as the principal ingredient for ‘shirumono’ or soups. In recent years around 1 400 tons (dry weight) of the species has been produced annually, almost 70% of which comes from its main sources. Besides Mie Prefecture, these include Fukushima, Shizuoka, Aichi, and Kagoshima Prefectures. Some basic studies have already been reported on Monostroma and substantial data is available on its morphology, life history, and ecology. These studies, centering on topics like morphology, pattern of growth and life history, indicate that this seaweed belongs to Monostroma latissimum (Kuetz.) Wittr. As for its morphology, it differs considerably according to the environment within which it grows. Furthermore, they may be classified into three types, namely the inner bay, estuary, and outer sea type, according to the external appearance of their mature fronds. To the inner bay type belongs cultured Monostroma as is evident from its leaf frond characteristics. Techniques of growing cultured Monostroma have yet to be developed to the level of ‘amanori’. One has so far depended on nature for seeding Monostroma, though more recent studies have led to the development of artificial methods that have since been applied widely. Artificial seeding of cultured Monostroma consists of culturing in tanks zygotes of the summer generation and artificially inducing adhesion of zoospores emerging in early Autumn on to seeding nets. The technique also facilitates easy retention of the seeding nets. On the other hand, increase in the number of culture nets of late has tended to overcrowd the culture grounds. At times this causes diseases of the leaf fronds and, accordingly, affects both the yield and quality of cultured Monostroma. Studies must now be taken up to stabilize production by installing the exact number of culture nets in the culture grounds according to their expected production. Research is also needed in the field of manufacturing technology for food products using Monostroma to help increase demand for this seaweed.