Species Of Aquatic Hyphomycetes Research Articles

Effects of metals on growth and sporulation of aquatic fungi

Aquatic hyphomycetes are a relevant group of fungi that play a crucial role as intermediaries between plant detritus and invertebrates in clean or metal-polluted streams. In this study, we investigated the effects of Zn, Cu, Ni, and Cd on the growth and sporulation of several aquatic hyphomycete species. Effects of these metals on growth were assessed in solid and liquid media with different compositions [1% malt extract (ME) and a mineral medium supplemented with vitamins and 2% glucose (MK)], and fungal sensitivity to metals was compared. The exposure to Zn or Cd inhibited the sporulation of Heliscus submersus and Tricladium chaetocladium, with these effects being stronger in the latter species. In solid medium, mydelial growth was linear, and, in most cases, metals negatively affected fungal growth. The sensitivity of aquatic hyphomycetes to metals, assessed as the metal concentration inhibiting biomass production in 50% (EC50), showed that Ypsilina graminea and Varicosporium elodeae were the most resistant species to Zn, while Alatospora acuminata, H. submersus, and Flagellospora curta appeared to be the most resistant fungus to Cu. Generally, lower toxicity of Zn or Cu than Ni or Cd was found. However, EC50 values were about 20 times higher in solid than in liquid medium. Changes in nutrient supplies to fungi affected metal toxicity, as shown by higher EC50 values in MK than ME. Complementarily, fungal tolerance to metals varied with fungal species as well as metal type.

Natural UVR Does Not Affect Decomposition by Aquatic Hyphomycetes

AbstractWe performed field and laboratory experiments to evaluate the effect of solar radiation (UVR and PAR) on leaf litter decomposition, fungal biomass and sporulation rates, in the Andean Patagonia, where high UVR levels are common. Leaves of Alnus glutinosa exposed to three treatments, normal radiation (PAR + UVR), protected from UVR and protected from total radiation (SHADE) by plastic films lost 31–37% of their mass. Leaves of Nothofagus pumilio lost 61–64% of their mass under the same conditions. For both leaf species, differences in mass losses among treatments were not statistically significant. Sporulation rates were significantly lower in the SHADE treatment. Fungal biomass accounted for 6.2 to 7.1% of leaf mass, without significant differences among treatments.In the laboratory, leaf discs of A. glutinosa colonized by single species of aquatic hyphomycetes (Articulospora tetracladia, Flagellospora curta or Lunulospora curvula) and exposed to or protected from UVR did not differ in mass loss and sporulation rates. Pure cultures of two fungal species grew at the same rates when exposed to light (PAR and PAR + UVR) or to the SHADE. In summary, we found no evidences that current high levels of UV radiation affect litter decomposition mediated by aquatic hyphomycetes. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Aquatic Hyphomycetes in the Parque Estadual das Fontes do Ipiranga - PEFI, São Paulo, Brazil

In the State Park Parque Estadual das Fontes do Ipiranga - PEFI, located in the city of Sao Paulo, samples of submerged mixed leaf litter were collected monthly from 10 sites with different levels of eutrophication, from October 2003 to April 2005. Some abiotic factors, such as pH, temperature, conductivity and dissolved oxygen were simultaneously measured in 20 cm deep water at each site. The leaf litter samples were washed in laboratory, cut into 1 cm2 pieces and incubated in Petri dishes containing distilled sterile water for five to seven days at 15 °C to 20 °C. Twenty-four aquatic Hyphomycete species were identified, with predominance of Anguillospora crassa Ingold, Lunulospora curvula Ingold, Tetrachaetum elegans Ingold and Camposporium pellucidum (Grove) Hughes. First reports for South America are: Anguillospora filiformis Greathead, Dendrospora erecta Ingold and Pyramidospora casuarinae Nilsson. These species, as well as Tetracladium setigerum (Grove) Ingold, Tricladium splendens Ingold and Varicosporium elodeae Kegel, are reported for the first time in Brazil. According to the multivariate analysis, the occurrence of the aquatic Hyphomycetes was mainly influenced by the trophic level of the aquatic environments.

Mixtures of zinc and phosphate affect leaf litter decomposition by aquatic fungi in streams

To better understand the impacts of multiple stressors in freshwaters, we investigated the effects of mixtures of zinc and inorganic phosphorus on microbial decomposition of leaf litter. Alder leaves were colonized in a stream and placed in microcosms with stream water supplemented or not with 3 concentrations of zinc (Zn up to 9.8 mg/l) or phosphate (P–PO 4 3− up to 0.5 mg/l), alone and in all possible combinations. We measured leaf mass loss, and fungal biomass, reproduction and diversity. In control microcosms, 23 species of aquatic hyphomycetes were identified on leaves, and the exposure to the highest zinc concentration reduced diversity to 14 species. Articulospora tetracladia was the dominant species followed by Flagellospora sp. and Alatospora acuminata. The exposure to phosphate increased the contribution of A. acuminata, but this species was negatively affected by zinc. Under high zinc stress, Varicosporium elodeae increased its contribution to the total conidial production. The exposure to high zinc concentration, alone or in mixtures with phosphate, led to shifts in fungal community structure, as indicated by cluster analysis based on sporulation data and denaturing gradient gel electrophoresis (DGGE) fingerprints of fungal DNA. These changes were accompanied by a reduction in leaf decomposition, particularly in mixtures with high Zn concentration, in which leaf mass loss was 30% lower than in the control. This suggests that the co-occurrence of zinc and phosphate may have negative effects on stream ecosystem functioning. However, we did not detect decreased leaf-associated fungal biomass and sporulation, probably because a delay in fungal colonization occurred due to the presence of stressors.

Metal stress induces programmed cell death in aquatic fungi

Aquatic hyphomycetes are a group of fungi that play a key role in organic matter turnover in both clean and metal-polluted streams. We examined the ability of Cu or Zn to induce programmed cell death (PCD) in three aquatic hyphomycete species through the evaluation of typical apoptotic markers, namely reactive oxygen species (ROS) accumulation, caspase-like activity, nuclear morphological alterations, and the occurrence of DNA strand breaks assessed by TUNEL assay. The exposure to both metals induced apoptotic events in all tested aquatic fungi. The most tolerant fungi either to Zn ( Varicosporium elodeae) or Cu ( Heliscus submersus) exhibited higher levels of PCD markers, suggesting that PCD processes might be linked to fungal resistance/tolerance to metal stress. Moreover, different patterns of apoptotic markers were found, namely a PCD process independent of ROS accumulation in V. elodeae exposed to Cu, or independent of caspase-like activity in Flagellospora curta exposed to Zn, or even without the occurrence of DNA strand breaks in F. curta exposed to Cu. This suggests that a multiplicity of PCD pathways might be operating in aquatic hyphomycetes. The occurrence of a tightly regulated cell death pathway, such as PCD, in aquatic hyphomycetes under metal stress might be a part of the mechanisms underlying fungal acclimation in metal-polluted streams, because it would allow the rapid removal of unwanted or damaged cells sparing nutrients and space for the fittest ones.

Leaf Decomposition in a Mountain Stream in the Sultanate of Oman

AbstractDecomposition of Juglans regia leaves was studied in fine and coarse mesh bags in a permanent mountain stream in Oman. A rapid initial mass loss, attributed to leaching, was followed by a more gradual decline. Daily exponential decay rates (k) calculated over 32 days were 0.011 (fine mesh litter bags) and 0.014 (coarse mesh litter bags). The difference between bag types was not significant, suggesting limited impact of leaf‐shredding invertebrates. Ergosterol levels on leaves from fine mesh bags peaked at 0.3 mg g–1 AFDM after 16 days of stream exposure.During the experimental period, which followed the annual leaf fall, the concentration of aquatic hyphomycete conidia in the stream varied between 82 and 1362 l–1. Based on the morphology of conidia found in the water column or released from leaves, we identified 14 species of aquatic hyphomycetes. Tetracladium apiense was the most common taxon (62.2% of conidia in water column during the field experiment). Three other Tetracladium species contributed another 8%. Plating out leaf particles yielded common epiphytic taxa such as Alternaria sp., Aureobasidium pullulans and Phoma sp.The measured metrics of leaf decay in this desert stream fall within the range of values observed in temperate and tropical streams, with clear evidence for an early leaching phase, and no evidence of a strong impact of leaf shredders. The community of aquatic hyphomycetes appears impoverished. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Reproduction and dispersal in aquatic hyphomycetes

The conidia of aquatic hyphomycetes were discovered by C.T. Ingold some 60 years ago. They are typically multiradiate or sigmoid, relatively fragile, and produced in enormous numbers. Their main function seems to be the rapid colonization of a periodic superabundance of leaves common in most streams. Conidia are unlikely to survive adverse conditions and to be responsible for the apparently worldwide distribution of many aquatic hyphomycete species. It has repeatedly been suggested that meiospores are responsible for long-distance dispersal; however, to date, only some 10% of described species have been connected to a teleomorph. To determine additional connections, and to document the potential role of meiospores in long-distance dispersal of aquatic hyphomycetes, the application of modern molecular methods is essential.

Diversity and activity of aquatic fungi under low oxygen conditions

Summary1. The objective was to test whether a decrease in oxygen concentration in streams affects the diversity and activity of aquatic hyphomycetes and consequently leaf litter decomposition.2. Senescent leaves of Alnus glutinosa were immersed for 7 days in a reference stream, for fungal colonization, and then incubated for 18 days in microcosms at five oxygen concentrations (4%, 26%, 54%, 76% and 94% saturation). Leaf decomposition (as loss of leaf toughness), fungal diversity, reproduction (as spore production) and biomass (ergosterol content) were determined.3. Leaf toughness decreased by 70% in leaves exposed to the highest O2 concentration, whereas the decrease was substantially less (from 25% to 45%) in treatments with lower O2. Fungal biomass decreased from 99 to 12 mg fungi g−1 ash‐free dry mass on exposure to 94% and 4% O2 respectively. Sporulation was strongly inhibited by reduction of dissolved O2 in water (3.1 × 104 versus 1.3 × 103 spores per microcosms) for 94% and 4% saturation respectively.4. A total of 20 species of aquatic hyphomycetes were identified on leaves exposed to 94% O2, whereas only 12 species were found in the treatment with 4% O2 saturation. Multidimensional scaling revealed that fungal assemblages exposed to 4% O2 were separated from all the others. Articulospora tetracladia, Cylindrocarpon sp. and Flagellospora curta were the dominant species in microcosms with 4% O2, while Flagellospora curvula and Anguillospora filiformis were dominant at higher O2 concentrations.5. Overall results suggest that the functional role of aquatic hyphomycetes as decomposers of leaf litter is limited when the concentration of dissolved oxygen in streams is low.

Elevated Aluminium Concentration in Acidified Headwater Streams Lowers Aquatic Hyphomycete Diversity and Impairs Leaf-Litter Breakdown

Aquatic hyphomycetes play an essential role in the decomposition of allochthonous organic matter which is a fundamental process driving the functioning of forested headwater streams. We studied the effect of anthropogenic acidification on aquatic hyphomycetes associated with decaying leaves of Fagus sylvatica in six forested headwater streams (pH range, 4.3-7.1). Non-metric multidimensional scaling revealed marked differences in aquatic hyphomycete assemblages between acidified and reference streams. We found strong relationships between aquatic hyphomycete richness and mean Al concentration (r = -0.998, p < 0.0001) and mean pH (r = 0.962, p < 0.002), meaning that fungal diversity was severely depleted in acidified streams. By contrast, mean fungal biomass was not related to acidity. Leaf breakdown rate was drastically reduced under acidic conditions raising the issue of whether the functioning of headwater ecosystems could be impaired by a loss of aquatic hyphomycete species.

The ecology of aero-aquatic hyphomycetes

We observed 35 species of aero-aquatic hyphomycetes belonging to 21 genera and 4 unidentified taxa of the Clavariopsis, Dactilella, Helicoon, and Tetracladium genera. Substrate preferences were detected in some species. Species such as Anguillospora longissima, Tetracladium marchalianum, and Fusarium aqueductum were found on different types of substrata. Only 11 species are developed on pine needles, while 20 species were observed on leaves. Eight species of aquatic hyphomycetes (Alatospora acuminata, Angullospora aquatica, Lemonniera aquatica, Tetracladium setigerum, Tricladium angulatum, Tripospermum campelopardus, Septonema secedens, and Spermospora sp.) were revealed on leaves taken from water habitats, whereas 15 species were found in litter. The jointly grown species did not demonstrate any inhibiting effects on each other except for Tripospermum campelopardus, which inhibited the growth of other species (Table 3). The microcyclic development of a Dactilella sp. was detected for the first time while being incubated on leaves in the laboratory. The frequency of appearance changes, and the diversity of the species of aquatic hyphomycetes appears to be higher on intact leaves than on skeletonized ones. The seasonal dynamics of aquatic hyphomycetes with two peaks of mass conidia development (vernal and sharper autumnal) were described. Some species were observed throughout the entire vegetation season. The conidial development in the leaf samples incubated in the laboratory lasted for 30–40 days. Therefore, the method of incubation for 7–10 days recommended in the literature did not allow for the complete investigation of species diversity in aquatic hyphomycetes.

Influence of conidial traits and leaf structure on attachment success of aquatic hyphomycetes on leaf litter

Attachment of conidia on leaves is a critical first step in the life cycle of aquatic hyphomycetes in streams. In a first series of microcosm experiments, attachment success of three common aquatic hyphomycete species differing in conidial shape (compact, filiform and tetraradiate) was determined on two leaf species, black alder and downy oak. Fungal species identity and leaf surface structure significantly affected conidial attachment after 24 h. The lower sides of oak leaves with extensive tufts trapped 2.4-8.8 more conidia than the upper sides of oak leaves and both sides of alder leaves. In a second experiment with seven fungal species, attachment success of two species with tetraradiate conidia was much greater than that of two other tetraradiate and three compact conidia, which all had similar attachment success. The species with the largest spores was also the most successful, but this pattern was not consistent across the size range of tested conidia. These results highlight the importance of leaf surface structure, possibly conidial shape and size and additional properties of aquatic hyphomycete conidia in determining attachment success on leaves and they point to the potential role of these factors in structuring fungal communities on decomposing leaves in streams.

Influence of conidial traits and leaf structure on attachment success of aquatic hyphomycetes on leaf litter

Attachment of conidia on leaves is a critical first step in the life cycle of aquatic hyphomycetes in streams. In a first series of microcosm experiments, attachment success of three common aquatic hyphomycete species differing in conidial shape (compact, filiform and tetraradiate) was determined on two leaf species, black alder and downy oak. Fungal species identity and leaf surface structure significantly affected conidial attachment after 24 h. The lower sides of oak leaves with extensive tufts trapped 2.4–8.8 more conidia than the upper sides of oak leaves and both sides of alder leaves. In a second experiment with seven fungal species, attachment success of two species with tetraradiate conidia was much greater than that of two other tetraradiate and three compact conidia, which all had similar attachment success. The species with the largest spores was also the most successful, but this pattern was not consistent across the size range of tested conidia. These results highlight the importance of leaf surface structure, possibly conidial shape and size and additional properties of aquatic hyphomycete conidia in determining attachment success on leaves and they point to the potential role of these factors in structuring fungal communities on decomposing leaves in streams.

Metal-binding proteins and peptides in the aquatic fungi Fontanospora fusiramosa and Flagellospora curta exposed to severe metal stress

The production of thiol-containing proteins/peptides and its role in metal-binding was examined in the aquatic hyphomycetes Fontanospora fusiramosa and Flagellospora curta exposed to Cu, Cd, or Zn at concentrations inhibiting the biomass production in 80%. Heat-treated cell-free extracts were separated by size-exclusion chromatography and the thiol and metal content in the fractions was determined. F. curta, the species tolerant to metals, showed higher absolute levels of thiol compounds, which bound higher amounts of Cu and Cd than F. fusiramosa. Peptides with very low molecular weight (<9 kDa), most likely glutathione and phytochelatins, were the major Cu- and Zn-binding components in both species of aquatic hyphomycetes. In most cases, proteins with high molecular weight (>26 kDa) were induced by metal ions and they were the major Cd-binding component in both species. Proteins with characteristics of metallothioneins were also induced by exposure to metals in both species, but they showed a minor role in metal-binding, suggesting they might have other functions in fungal cells.

Streams in Quebec boreal and mixed-wood forests reveal a new aquatic hyphomycete species, Dwayaangam colodena sp. nov.

Foam from eight streams in boreal and mixed-wood forests in Québec were sampled in early and late fall 2002 to evaluate the biodiversity of their aquatic hyphomycete communities. Two regions were studied: 53-54 degrees N and 46-49 degrees N. A total of 54 species were identified. Twenty taxa were found only in the northern region, and four were unique to the southern region. A new aquatic hyphomycete, Dwayaangam colodena sp. nov., was found mostly in northern streams. It is described along with its taxonomic position.

Streams in Quebec boreal and mixed-wood forests reveal a new aquatic hyphomycete species, Dwayaangam colodena sp. nov.

Foam from eight streams in boreal and mixed-wood forests in Québec were sampled in early and late fall 2002 to evaluate the biodiversity of their aquatic hyphomycete communities. Two regions were studied: 53–54°N and 46–49°N. A total of 54 species were identified. Twenty taxa were found only in the northern region, and four were unique to the southern region. A new aquatic hyphomycete, Dwayaangam colodena sp. nov., was found mostly in northern streams. It is described along with its taxonomic position.

Aquatic hyphomycete diversity and identity affect leaf litter decomposition in microcosms

We conducted a microcosm experiment with monocultures and all possible combinations of four aquatic hyphomycete species, Articulospora tetracladia, Flagellospora curta, Geniculospora grandis and Heliscus submersus, to examine the potential effects of species richness on three functional aspects: leaf litter decomposition (leaf mass loss), fungal production (ergosterol buildup) and reproductive effort (released spores). Both species richness and identity significantly affected fungal biomass and conidial production (number and biomass of released spores), whereas only species identity had a significant effect on leaf mass loss. In mixed cultures, all measures of fungal functions were greater than expected from the weighted performances of participating species in monoculture. Mixed cultures outperformed the most active monoculture for biomass accumulation but not for leaf mass loss and conidial production. The three examined aspects of aquatic hyphomycete activity tended to increase with species richness, and a complementary effect was unequivocally demonstrated for fungal biomass. Our results also suggest that specific traits of certain species may have a greater influence on ecosystem functioning than species number.

Do Invertebrate Activity and Current Velocity Affect Fungal Assemblage Structure in Leaves?

AbstractIn this study we assessed the effect of current velocity and shredder presence, manipulated in artificial channels, on the structure of the fungal assemblage colonizing alder (Alnus glutinosa (L.) Gaertner) leaves incubated in coarse and fine mesh bags. Fungal sporulation rates, cumulative conidial production and number of species of aquatic hyphomycetes were higher in leaves exposed to high rather than to low current velocity. The opposite was observed regarding Simpson's index (D) on the fungal assemblage. Some species of aquatic hyphomycetes were consistently stimulated in high current channels. No effect of shredders or of mesh type was observed. (© 2006 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Vegetation diversity increases species richness of leaf-decaying fungal communities in woodland streams

Submerged leaf litter is a vital resource for many aquatic species in wood- land streams. However, forestry tends to lower the diversity of litter entering streams, which potentially impacts leaf-dependent species and the entire detritus-based food web. To overcome this problem, a guideline for sustainable forestry and ecosystem conservation lies in increasing litter diversity in managed forests. However, the way in and the extent to which such an increase changes the leaf decomposer communities are mostly unknown. In the present study, fungal communities were surveyed bimonthly in ten woodland headwater streams with contrasting tree diversity resulting in various proportions of leaf species in litter. A total of 79 aquatic hyphomycete species identi- fied from conidia in stream water were listed. The differences in conidial abundance, richness and diversity between communities from the ten streams suggested a strong effect of local abundance and composition of leaf litter. Conidial abundance clearly distinguished two sets of streams, one dominated by oaks and hazel and the other by beech. The fungal richness in the ten streams showed a positive and significant corre- lation with the leaf species richness, accounting for 44 % of the total variance among streams. About 50 % more fungal species were found in streams with the highest leaf litter diversity, and several species were more frequent in such streams. No distinct species assemblages were however associated with any particular leaf species. These findings were interpreted as resulting from substrate preferences, but not specificity by the fungal species. This is supported by a manipulation in which the addition of a bulk of hazel leaves in a stream dominated by beech did not result in an increase in fungal richness over three months. Seasonal changes appeared to be the main factor controll- ing fungal species abundance. Overall, the results suggest a hierarchical pattern be- tween riparian and aquatic biodiversity and provide an argument for the conservation of diverse tree species along streams.

Riparian plant species loss alters trophic dynamics in detritus-based stream ecosystems

Riparian vegetation is closely connected to stream food webs through input of leaf detritus as a primary energy supply, and therefore, any alteration of plant diversity may influence aquatic ecosystem functioning. We measured leaf litter breakdown rate and associated biological parameters in mesh bags in eight headwater streams bordered either with mixed deciduous forest or with beech forest. The variety of leaf litter types in mixed forest results in higher food quality for large-particle invertebrate detritivores ('shredders') than in beech forest, which is dominated by a single leaf species of low quality. Breakdown rate of low quality (oak) leaf litter in coarse mesh bags was lower in beech forest streams than in mixed forest streams, a consequence of lower shredder biomass. In contrast, high quality (alder) leaf litter broke down at similar rates in both stream categories as a result of similar shredder biomass in coarse mesh bags. Microbial breakdown rate of oak and alder leaves, determined in fine mesh bags, did not differ between the stream categories. We found however aquatic hyphomycete species richness on leaf litter to positively co-vary with riparian plant species richness. Fungal species richness may enhance leaf litter breakdown rate through positive effects on resource quality for shredders. A feeding experiment established a positive relationship between fungal species richness per se and leaf litter consumption rate by an amphipod shredder (Gammarus fossarum). Our results show therefore that plant species richness may indirectly govern ecosystem functioning through complex trophic interactions. Integrating microbial diversity and trophic dynamics would considerably improve the prediction of the consequences of species loss.

Aquatic hyphomycetes and leaf decomposition in contaminated groundwater wells in Central Germany

Six heavy metal contaminated groundwater wells near abandoned copper shale mines of Mansfelder Land in Central Germany yielded 13 aquatic hyphomycete species (3-7 per site) on immersed Alnus glutinosa leaves. Anguillospora sp. 2, Cylindrocarpon sp. and Tetracladium marchalianum were the three top conidial producers. Mass loss rates and release of conidia were below those of leaves exposed in surface streams with similar or higher heavy metal loads, while ergosterol levels were comparable. In food choice experiments, Gammarus fossarum distinguished between leaves conditioned in the six wells. Consumption rates correlated with numbers of released conidia but not with ergosterol levels of the substrate.