Molecular and morphological relationships between two closely related species, Turbinaria ornata and T. conoides (Sargassaceae,Phaeophyceae)

We employed four markers (two chloroplastic, one mitochondrial and one nuclear) to investigate whether Turbinaria ornata and Turbinaria conoides, two morphologically similar brown algae, are distinct species. The molecular data revealed reciprocal monophyly, thus confirming the two algae as discrete species. Nevertheless, taxonomical ambiguities remain. T. conoides is more morphologically variable than T. ornata. We identified an atypical T. conoides morphotype whose blade possesses intramarginal teeth, a morphological characteristic of the T. ornata group that is normally absent within T. conoides. The molecular data indicate, nonetheless, that this morphotype belongs genetically to the T. conoides group. Thus, the results cast doubt upon the validity of using intramarginal teeth for species diagnosis.     

Population Dynamics of Meloidogyne incognita on Corn Grown in Soil in Fested with Arthrobotrys conoides

Microplot and greenhouse experiments were conducted to evaluate the effects of soil incorporation of the nematophagous fungus Arthrobotrys conoides and green alfalfa mulch on the population dynamics of Meloidogyne incognita on corn. Reproduction of M. incognita and the incidence of root galling were reduced by the addition of A. conoides and/or green alfalfa in all tests. Numbers of juveniles were reduced by as much as 84%, and eggs were fewest in early to mid-season soil samples from microplots. Yields increased in treatments with A. conoides and/or green alfalfa in greenhouse tests and in the microplot tests in 1979. No interaction was found between the fungus and green alfalfa in the reduction of the nematode population.     

Interaction of nematodes with nematophagus fungi: induction of trap formation, attraction and detection of attractants

Induction of trap formation in Arthrobotrys oligospora, A. conoides and Monacrosporium cystosporum was studied during a 24 h period in the presence of the free-living nematodes Panagrellus redivivus on various nutrient media. A definite pattern of trap formation was observed in these fungi. Low nutrient mineral salt medium had the most pronounced effect on trap formation. Attraction and repulsion of P. redivivus towards these three nematophagous and three non-nematophagous fungi was studied. The nematodes were attracted towards three nematophagous and one non-nematophagous fungi, the other two repelled them. Attractants of the nematophagous fungi were determined by thin-layer chromatography. In the case of A. oligospora and M. cystosporum, four spots were traced, whereas in A. conoides, five spots were detected.     

The Effect of Arthrobotrys conoides on Meloidogyne incognita Population Densities in Corn as Influenced by Temperature,Fungus Inoculum Density,and Time of Fungus Introduction in the Soil

In greenhouse experiments, the effect of Arthrobotrys conoides on Meloidogyne incognita population densities as affected by soil temperature, inoculum density, and green alfalfa was determined. The effect on M. incognita population densities was greater at a soil temperature of 25 C than at 18 or 32 C. Nematode control by A. conoides was most effective when the fungus was introduced into the soil 2 wk prior to nematode inoculation and planting of corn. Inoculum density of A. conoides was positively correlated with plant shoot weight (r = 0.81) and negatively correlated with numbers of Meloidogyne juveniles (r = -0.96), eggs (-0.89) and galls per gram of root (-0.91). A. conoides was not isolated from green alfalfa, but was isolated from alfalfa-amended soil to which no fungus had been added.     

Application of seaweeds for the removal of lead from aqueous solution

Ten different seaweed species were compared on the basis of lead uptake at different pH conditions. The brown seaweed, Turbinaria conoides, exhibited maximum lead uptake (at pH 4.5) and hence was selected for further studies. Sorption isotherms, obtained at different pH (4–5) and temperature (25–35 °C) conditions were fitted using Langmuir and Sips models. According to the Langmuir model, the maximum lead uptake of 439.4 mg/g was obtained at optimum pH (4.5) and temperature (30 °C). The Sips model better described the sorption isotherms with high correlation coefficients at all conditions examined. Various thermodynamic parameters such as ΔG°, ΔH° and ΔS° were calculated indicating that the present system was a spontaneous and endothermic process. Through potentiometric titrations, number of binding sites (carboxyl groups) and pK₁ were determined as 4.1 mmol/g and 4.4, respectively. The influence of co-ions (Na⁺, K⁺, Mg²⁺ and Ca²⁺) on lead uptake was well pronounced in the case of divalent ions compared to monovalent ions. The solution of 0.1 M HCl successfully eluted all lead ions from lead-loaded T. conoides biomass. The regeneration experiments revealed that the alga could be successfully reused for five cycles without any loss in lead biosorption capacity. A glass column (2 cm i.d. and 35 cm height) was used to study the continuous lead biosorption performance of T. conoides. At 25 cm (bed height), 5 ml/min (flow rate) and 100 mg/l (initial lead concentration), T. conoides exhibited lead uptake of 220.1 mg/g. The column was successfully eluted using 0.1 M HCl, with elution efficiency of 99.7%.     

Removal of rhodamine B from aqueous solution by sorption on Turbinaria conoides (Phaeophyta)

The ability of the brown seaweed, Turbinaria conoides to absorb rhodamine B (RB) from aqueous solution was investigated in a batch system. The effects of various experimental parameters (e.g., morphology, initial dye concentration, temperature, and pH) were investigated and optimal experimental condition was ascertained. The results revealed that sorption capacity of T. conoides increased with increasing temperature, and decreasing initial dye concentration and pH. Sorption equilibrium studies using Langmuir and Freundlich models demonstrated that RB biosorption fitted well to the Langmuir isotherm. This study suggested that T. conoides can be used as a potential biosorbent for the removal of RB from wastewater.     

Volatile halocarbon emissions by three tropical brown seaweeds under different irradiances

The emission rates of eight volatile halogenated compounds by three tropical brown seaweed species collected from Cape Rachado, west coast Peninsular Malaysia, under different irradiances have been determined. A purge-and-trap sample preparation system with a gas chromatograph and mass-selective detector was used to measure a suite of halocarbons released by Sargassum binderi Sonder ex J. Agardh, Padina australis Hauck, and Turbinaria conoides (J. Agardh) Kützing. All species are widely distributed in Peninsular Malaysia, with S. binderi a dominant seaweed species at our survey site. Release of few halocarbons was found to be influenced by irradiance. Correlations were also observed between emission of certain halocarbons with photosynthetic activity, especially bromo-and iodinated compounds (0.6?<?r?<0.9; p?<?0.01) suggesting that environmental factors such as light can affect the release of these volatile halogenated compounds by the seaweeds into the atmosphere. Compared with temperate and polar brown seaweeds, tropical species, such as T. conoides, may emit higher levels of bromoform, CHBr₃, and other halocarbons. It is therefore important to investigate the contribution of tropical seaweeds towards the local atmospheric composition of halocarbons.     

Development,Distribution, and Host Studies of the Fungus Macrobiotophthoira vermicola (Entomophthorales)

The life cycle and host range of Macrobiotophthora vermicola were studied. Secondary spores produced from forcibly ejected primary spores adhered to the cuticle of Cruznema tripartitum, germinated, and penetrated the cuticle within 30 minutes. New primary spores were produced within 24 hours of initial spore adhesion. In a host range study, species of Rhabditidae, Diplogasteridae, and Aphelenchoidea were hosts, but not species of Bunonematidae, Tripylidae, Cephalobida, or Tylenchina. Numbers of second-stage Meloidogyne incognita juveniles were not decreased when added to soil seeded with infected C. tripartitum. In six Tennessee soybean fields, Macrobiotophthora vermicola was the most commonly encountered nematode-destroying fungus, followed by a sterile, nonseptate fungus and Arthrobotrys conoides. Nematophagous fungi were isolated more frequently from silt loam soils than from clay soils. Addition of C. tripartitum to soil extract plates as a bait nematode did not increase isolations of nematophagous fungi.     

Interaction of Mercuric Ions with Different Marine Algal Species

The use of different seaweeds such as Sargassum sp., Turbinaria conoides, and Ulva sp. in removing mercury(II) from aqueous solutions were investigated. The initial experimental runs, conducted at different equilibrium pH conditions, demonstrated that brown seaweeds outperformed green seaweed in Hg(II) biosorption at all pH conditions. In particular, at pH 5, maximum biosorption capacities of 170.3 and 145.8 mg/g were recorded for the brown seaweeds T. conoides and Sargassum sp., respectively, compared with 138.4 mg/g for the green seaweed Ulva sp. Isotherm data were modeled and interpreted using the Langmuir, Freundlich, Redlich-Peterson, and Toth models, with the latter described the Hg(II) isotherms with high correlation coefficients and low % error values. The kinetic data indicate the rapidity of the biosorption process, with the equilibrium achieved within 90 min. Several models, including the Elovich, pseudo-first-order, and pseudo-second-order models, were examined for their suitability with the present data; the correlation coefficient and % error values, along with better prediction of equilibrium uptake values, favored the pseudo-first-order model. The desorption experiments were highly successful for T. conoides biomass with 0.05 M HCl, whereas for the other two seaweeds, 0.05 M HCl resulted in high biomass weight loss. Reusing T. conoides biomass in three successive sorption-desorption cycles resulted in only 8.8% reduction in Hg(II) biosorption capacity compared with its original uptake.     

Isolation of turbinaric acid as a chemomarker of Turbinaria conoides (J. Agardh) Kützing from South Pacific Islands

Several species of the genus Turbinaria coexist along the coasts of islands in the Indian and Pacific Oceans. Among these brown algae, Turbinaria ornata and T. conoides are sister species that are difficult to differentiate using exclusively morphological characters. Based on in vivo nuclear magnetic resonance and chromatographic techniques, i.e., liquid and gas chromatography‐mass spectrometry analysis, combined with phylogenetic data, we successfully identified turbinaric acid in T. conoides samples from several Indian and Pacific Ocean islands. This nonvariable discriminant molecule was only identified in T. conoides specimens, but not in the two allied species T. ornata and T. decurrens. Results are discussed with regard to turbinaric acid as an interesting chemomarker isolated from T. conoides and the rapid discrimination of Turbinaria specimens using chemical assays.     

Production of nematode-attracting and nematicidal substances by predacious fungi

Arthrobotrys conoides Drechsler,Arthrobotrys oligospora Fressenius andMonacrosporium rutgeriensis R. C. Cooke, Pramer belong to the peculiar group of predactious fungi which trap and kill nematodes. We have found that these cultures produce nematode-attracting and nematicidal substances the production of which is potentiated in the presence of nematodes. Our method of nematode attraction assay is also described.     

Meristoderm in Turbinaria conoides (Fucales,sargassaceae)

In Turbinaria conoides (J. Agardh) Kützing, the hapteron, thallus and receptacle meristoderm cells are columnar, polarized and have thick longitudinal walls. In the thallus apical cavity, however, these cells are elongate and possess cap-like structures and thin, longitudinal walls. The meristoderm cells, except for those present at the apical cavities and ostiole regions, are overarched by 1–5 extracellular layers that are deposited in an orderly manner.The histochemistry of the meristoderm suggests that its cell walls contain alginic acid, cellulose and sulphated polysaccharides. The extracellular layers and the materials in the cap-like structures contain a mixture of alginic acid and sulphated polysaccharides, and little cellulose. The possible role of meristoderm cells lining the apical cavity of the thallus and that of extracellular layers is discussed.     

Effects of nutrient enrichment and herbivory on morphology,reproduction and chemical content of Turbinaria conoides (Phaeophyceae)

The effects of nutrient enrichment and herbivory on resource allocation patterns among morphology, reproduction, and chemical content of the brown alga, Turbinaria conoides (J. Agardh) Kützing were tested in the shallow subtidal zone of the Gulf of Thailand. The field experimental design comprised 36 plots (50 × 50 cm²) with and without herbivores, and two nutrient levels. Cages (uncaged and fully caged plots) were used to exclude herbivorous fishes and two nutrients levels were achieved by experimental enrichment above ambient nutrient concentrations. For morphology of Turbinaria, the maximum length (holdfast to frond apex), the width of the base of the stipe, number of blades, holdfast and stipe diameter were measured. Biomass, reproductive output, and tissue nutrient (carbon: nitrogen: phosphorus) content of T. conoides were examined. Phlorotannin concentrations were examined using a modified Folin‐Ciocalteu method. The results showed that herbivory had no effect on morphology, reproduction, or phlorotannin concentrations. This could be due to the structural and morphological deterrents of alga, which might minimize grazing effects from herbivorous fishes. Nutrient enrichment had no effect on morphology and reproduction of T. conoides, possibly due to low nutrient demand in Turbinaria. However, nutrient enrichment did affect phlorotannin concentrations, as phlorotannins in the enriched plots were lower than the ambient plots. These results support, in part, the carbon–nutrient balance hypothesis that states algae will allocate fewer resources to production of anti‐herbivore chemical compounds when enriched with potential growth‐limiting nutrients.     

Volatile Substances Produced by Fusarium oxysporum from Coffee Rhizosphere and Other Microbes affect Meloidogyne incognita and Arthrobotrys conoides

Microorganisms produce volatile organic compounds (VOCs) which mediate interactions with other organisms and may be the basis for the development of new methods to control plant-parasitic nematodes that damage coffee plants. In the present work, 35 fungal isolates were isolated from coffee plant rhizosphere, Meloidogyne exigua eggs and egg masses. Most of the fungal isolates belonged to the genus Fusarium and presented in vitro antagonism classified as mutual exclusion and parasitism against the nematode-predator fungus Arthrobotrys conoides (isolated from coffee roots). These results and the stronger activity of VOCs against this fungus by 12 endophytic bacteria may account for the failure of A. conoides to reduce plant-parasitic nematodes in coffee fields. VOCs from 13 fungal isolates caused more than 40% immobility to Meloidogyne incognita second stage juveniles (J₂), and those of three isolates (two Fusarium oxysporum isolates and an F. solani isolate) also led to 88-96% J₂ mortality. M. incognita J₂ infectivity decreased as a function of increased exposure time to F. oxysporum isolate 21 VOCs. Gas chromatography-mass spectrometry (GC-MS) analysis lead to the detection of 38 VOCs produced by F. oxysporum is. 21 culture. Only five were present in amounts above 1% of the total: dioctyl disulfide (it may also be 2-propyldecan-1-ol or 1-(2-hydroxyethoxy) tridecane); caryophyllene; 4-methyl-2,6-di-tert-butylphenol; and acoradiene. One of them was not identified. Volatiles toxic to nematodes make a difference among interacting microorganisms in coffee rhizosphere defining an additional attribute of a biocontrol agent against plant-parasitic nematodes.     

Morphological and molecular characterization,predatory behaviour and effect of organic extracts of four nematophagous fungi from Mexico

Four nematophagous fungi (NF) were identified by traditional and molecular techniques, and their in vitro predatory activity (PA) against Haemonchus contortus (Hc), and Panagrellus redivivus (Pr) was assessed. Additionally, the nematocidal activity (NA) of fungal organic extracts (OEs) obtained from a methanol/dichloromethane system was assessed. Fungi were grown in PDB medium under shaking (SchC) and static conditions (StatC). The PA of Arthrobotrys conoides (Ac), A. oligospora (Ao), A. arthrobotryoides (Aa) and Purpureocillium lilacinum (Pl) against Hc were 75, 71, 66 and 52%, respectively. Meanwhile, the PA against Pr for same fungal genera/species were 99.8, 99.9, 99.4 and 96.3%, respectively. The highest NA of the OEs were 89.5, 81.6 and 72.1% for Aa, Ac and Ao, respectively, under StatC. Moreover, Pl cultured under SchC caused 78% Hc larval mortality. The four assessed NF and their OEs are promising candidates as potential biocide agents against parasitic nematodes.     

Biological control of sheep parasite nematodes by nematode-trapping fungi: <Emphasis Type="Italic">in vitro</Emphasis> activity and after passage through the gastrointestinal tract

Summary The main method used for the control of gastrointestinal nematodes in sheep production is the application of chemotherapeutic agents, which often lead to the selection of parasites resistant to given active principles. Biological control can be considered a promising alternative, contributing to an increase in the efficacy of verminous control. We determined the in vitro activity and in situ survival of the predatory fungi Arthrobotrys musiformis and Arthrobotrys conoides during passage through the gastrointestinal tract of sheep after oral administration of conidia in microencapsulated form and as a liquid in natura. Initial in vitro tests showed that both fungi were efficient in the predation of trichostrongylid L3 larvae present in the faeces of sheep naturally infected with gastrointestinal nematodes. The fungi presented high nematophagous activity, which was 99.3% for A. conoides and 73.7% for A. musiformis. A. conoides did not survive passage through the gastrointestinal tract under the conditions of the present experiment. On the other hand, A. musiformis was reisolated after administration in either microencapsulated or liquid form, suggesting that this species is a promising alternative for the control of nematodes in sheep since it survives without any protection (in natura).     

Extraction and characterisation of alginate from brown seaweeds (Fucales,Phaeophyceae) collected from Port Dickson,Peninsular Malaysia

Four species of brown seaweeds, namely Sargassum baccularia, Sargassum binderi, Sargassum siliquosum and Turbinaria conoides, harvested from Port Dickson, Negeri Sembilan, Malaysia were analysed for ash content, alginate yield and alginate properties. Seaweeds calcined at 450°C were found to have low amount of non-combustible residue as these were not contaminated by calcareous animals. Alginate was extracted from these seaweeds by two methods: hot and cold. In the hot method, the storing time was 3 h and the processing temperature was 50°C, whilst in the cold method, the sample was stored overnight at room temperature. Higher yield of alginate was obtained by the hot method compared to the cold method, but alginate extracted by the cold method gave higher molecular weight. In the hot method, 49.9% of alginate was extracted from S. siliquosum, followed by T. conoides (41.4%), S. binderi (38.9%) and S. baccularia (26.7%). Alginate extracted from T. conoides has an average molecular weight, M _w, of 8.06 × 10⁵ g mol⁻¹, whereas alginate from S. siliquosum was the lowest in M _w (4.81 × 10⁵ g mol⁻¹) when the extraction was done at room temperature. Alginate extracted from S. baccularia was found to be very heat-sensitive. Its M _w has dropped more than 83%, from 7.52 × 10⁵ to 1.23 × 10⁵ g mol⁻¹, when the extraction temperature was raised. The effect of heat on the extent of depolymerisation of the alginate molecule of the other three brown seaweed species was less significant, with decrease in molecular weight ranging between 13% and 16%.