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Diel temperature oscillations are a nearly ubiquitous phenomenon, with amplitudes predicted to change along with mean temperatures under global-warming scenarios. Impact assessments of global warming have largely disregarded diel temperature oscillations, even though key processes in ecosystems, such as decomposition, may be affected. We tested the effect of a 5°C temperature increase with and without diel oscillations on litter decomposition by fungal communities in stream microcosms. Five temperature regimes with identical thermal sums (degree days) were applied: constant 3° and 8°C; diel temperature oscillations of 5°C around each mean; and oscillations of 9°C around 8°C. Temperature oscillations around 8°C (warming scenario), but not 3°C (ambient scenario), accelerated decomposition by 18% (5°C oscillations) and 31% (9°C oscillations), respectively, compared to the constant temperature regime at 8°C. Community structure was not affected by oscillating temperatures, although the rise in mean temperature from 3° to 8°C consistently shifted the relative abundance of species. A simple model using temperature—growth responses of the dominant fungal decomposers accurately described the experimentally observed pattern, indicating that the effect of temperature oscillations on decomposition in our warming scenario was caused by strong curvilinear responses of species to warming at low temperature, particularly of the species becoming most abundant at 8°C (Tetracladium marchalianum). These findings underscore the need to consider species-specific temperature characteristics in concert with changes in communities when assessing consequences of global warming on ecosystem processes.

A proper management of water resources determines a response to various anthropogenic interventions allowing the implementation of diagnostic feasible methods to the water sources. This is done using bioindicators, organisms that can indicate the environmental changes effects. The aquatic hyphomycetes are indicators of water quality, varying their presence depending on the degree of environmental affectation. The aim of this study was to evaluate water quality in areas with and without enviromen-tal affectation of Cupira River (La Cumaca, Carabobo State, Venezuela) using microbiological biomarkers and chemical pa-rameters. Weekly samplings were carried out for a year (March 2008 to February 2009) in three zones of the river: headwater (unaffected), intermediate (recreational use) and significantly affected area (near a quarry and cattle grazing), where physicochemical parameters (dissolved oxygen, conductivity, pH, temperature and total solids) were determined, as well as nutrients, total coliforms, fecal coliforms and aquatic hyphomy-cetes (number of species and conidia/ml). Compared with the area unaffected, the total solids, total coliforms number and fecal coliforms increased in the significantly affected area, while the number of species and frequency of conidia decreased. The most frequent species that characterized the community of aquatic hyphomycetes of the Cupira River was Flabellospora crassa, although other species also showed high frequency values: Flagellospora curvula, Clavatospora tentacula, Campylospora sp., Helicomyces torquatus, Alatospora acuminata, Anguillospora crassa, Brachiosphaera tropicalis, Camposporium pellucidum, Phalangispora constricta, Phalangispora nawawii, Flabellospora verticillata and Campylospora chaetocladia.

Previous studies which have tested the feeding preferences of shredders for fungal species and the food quality of fungi used detritus uniformly colonized by a fungus, which is not the case for decaying leaves in streams. It is not known whether shredders in different development stages exhibit variations in feeding preference and larval performance. This study examined the feeding preferences and the growth of the third and the fifth instars of Pycnopsyche gentilis larvae using fungal-colonized patches and whole leaves, respectively, having different fungal species compositions (Alatospora acuminata, Anguillospora filiformis, Articulospora tetracladia, Tetrachaetum elegans, and all species combined). The aquatic hyphomycetes used were co-dominant on leaves in the stream inhabited by the caddisfly. During 14 d of feeding, the larvae of both instars did not show significant differences in feeding preferences for the patches growing on oak leaves, although the third instar larvae were slightly more selective than the fifth instar larvae. When fed with maple leaves for 18 d, larval growth rates, gross growth efficiencies, and survivorship were not significantly different among the fungal treatments. However, the larval growth of both instars fed with fungal-colonized leaves was always significantly greater than the growth of larvae fed with diets of uncolonized leaves. The third instar larvae grew faster than the fifth instar larvae, but the growth efficiencies of the two instars were similar. These results suggest that P. gentilis larvae exhibit less selectivity in their feeding than other caddisfly shredders that have been examined and that the dominant fungi colonizing leaves in their habitat are similar in palatability and food quality for this shredder.

Twenty-six species of aquatic hyphomycetes were isolated from woody sources (unidentified wood segments, leaf skeletons and neck of leaves and bark) in the North River Nile (Delta region). Alatospora acuminata, Anguillospora crassa, Flagellaspora penicillioides, Lunulospra curvula, Tetracladium marchalianum and Triscelophorus monosporus were the most common species. Temperature was the highest physico-chemical parameter affecting the aquatic hyphomycetes occurrence. Twelve species of hyphomycetes, isolated from woody substrates, were screened for their ability to produce extracellular lignocellulolytic enzymes on solid media. The enzymes tested included: endoglucanase, endoxylanase, beta-glucosidase, laccase, peroxidase, polyphenoloxidase, tyrosinase and beta-xylosidase. Three species, A. acuminata, F. penicillioides, T. monosporus, were positive for all tested enzymes. Also, A. longissima was positive for all enzymes except lignin-peroxidase. The ability to produce cellulase was 100% for all species while only, four species were positive for lignin-peroxidase. The ability of the species to produce other lignocellulotic enzyme ranged from 50% to 83%. Freshwater hyphomycetes have been shown to produce a rich array of enzymes able to degrade the polysaccharides of plant debris.

The effects of iron and manganese on the growth and reproduction of three aquatic hyphomycetes, Alatospora acuminata, Tetrachaetum elegans and Articulospora tetracladia, were assessed in the laboratory. Previous studies had indicated that T. elegans and A. acuminata appeared not to colonize leaf material below a discharge from an abandoned coal mine, whereas the distribution of A. tetracladia was not affected by this effluent. The principal contaminants of this effluent were iron and manganese. Neither iron nor manganese had inhibitory effects on the growth of the three species investigated. Indeed, mycelial extension rates of A. tetracladia were stimulated by the presence of iron. Reproduction was however, affected, with the sporulation of both T. elegans and A. acuminata being significantly reduced by exposure to either iron or manganese. By contrast, no significant effect on sporulation of A. tetracladia was observed. There was no significant effect of either metal on conidial germination of the three species. The apparent field distribution of fungi was related to their sensitivities to metals in the laboratory. Those species which appeared to be excluded by the discharge produced few or no conidia when exposed to metals at concentrations equivalent to those recorded at the contaminated site. Since conidia were used to detect aquatic hyphomycetes, it is unclear whether A. acuminata and T. elegans were indeed absent below the discharge or were present as mycelium which, being unable to sporulate, cannot be identified.

Quantitative ELISAs have been developed to determine the biomass of two aquatic hyphomycetes in natural mixed assemblages. These assays employ a species specific rat monoclonal antibody (MAb) raised to Alatospora acuminata and a genus-specific murine MAb raised to Tetracladium marchalianum The respective antigens are produced constitutively and their production is not affected by a range of culture conditions. The MAbs can also be used to study the spatial distribution of these fungi using immunofluorescence Both antibodies recognize carbohydrate epitopes and belong to the immunoglobulin class IgM. The potential applications of these immunoassays are discussed.

Specific monoclonal antibodies raised in previous studies were used in a quantitative ELISA to determine the biomass of three species of aquatic hyphomycetes: Tetracladium marchalianum de Wild, Anguillospora longissima Ingold, and Alatospora acuminata Ingold. The use of these methods for the study of mixed assemblages was assessed in the laboratory. The presence of nontarget fungi did not interfere with specific recognition by antibodies in the ELISA assay. The immunoassays indicated that lower biomass was attained by individual species colonizing field-incubated leaf material compared to laboratory-inoculated material. Alatospora acuminata attained the highest relative biomass on field-incubated leaf material, and T. marchalianum the lowest. These results contrast sharply with those obtained using more conventional methods based on conidial abundance. Conidia of T. marchaliamum were recorded more frequently than conidia of A. acuminata, and are, therefore, assumed to have had a higher relative abundance. The implications of these apparently conflicting results are discussed.

We followed the dynamics of oak leaf degradation caused by eight species of aquatic Hyphomycetes and determined their palatability to caddisfly (Trichoptera) detritivores. All species of ftingi caused weight loss and increased ATP concentrations of oak leaves although the magnitude of these changes varied considerably among fungal species. All species except Heliscus lugdunensis caused softening of oak leaves. Heliscus lugdunensis and Tetracladium marchalianum exhibited less potential for oak leaf degradation a) than other species and b) than they have previously displayed on other types of leaves. Caddisfly larvae expressed distinct preferences for oak leaves colonized by Alatospora acuminata and Flagellospora curvula. Leaves colonized by Clavariopsis aquatica were intermediate in preference rankings, while leaves colonized by the remaining five fungi were relatively unpalatable.

We examined the food quality of different fungi by determining growth, consumption and survivorship of two caddisflies fed diets of aspen leaves colonized by single fungal species. Mid-to-late fifth instar larvae of Hesperophylax magnus grew better on leaves colonized by Alatospora acuminata, Flagellospora curvula or Tetracladium marchalianum than on leaves colonized by Lemonniera aquatica or on stream detritus, but differences in instantaneous growth rates on these diets were not statistically significant. For early fifth instar larvae of Psychoglypha sp., we detected statistically significant differences in instantaneous growth rates on the following diets: F. curvula = A. acuminata > Heliscus lugdunensis = Articulospora inflata > L. aquatica = stream detritus. Psychoglypha sp. larvae also exhibited high survivorship on these diets through 20 d, but experienced 100% mortality when fed leaves colonized by Filosporella annelidica or T. marchalianum. Psychoglypha sp. larvae grew significantly faster on aspen leaves fully conditioned (10 d and 20 d) by F. curvula and H. lugdunensis than on preconditioned leaves (4 d). For both caddisflies, consumption rates were higher on diets that supported higher growth rates. Food quality of all four fungi in the Hesperophylax experiment and four of the seven fungi in the Psychoglypha experiment corresponded well with caddisfly preferences we have previously determined. Food quality was affected by fungal species and conditioning time. However, even well-conditioned leaves did not support high growth rates in caddisflies if the leaves were colonized by low quality fungi.