Assimilation Efficiency of Gammarus pseudolimnaeus (Amphipoda) Feeding on Fungal Mycelium or Autumn-Shed Leaves

Kendrick, Bryce; Bärlocher, Feli×

doi:10.2307/3543277

Cited by 122 publications

(79 citation statements)

References 18 publications

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“…Pre-moulting clearance of the gut has also been reported for the isopod Idotea baltica Pallas, by Strong & Daborn (1980) . The calculated fast gut passage times are in line with those obtained for Gammarus pseudolimnaeus ; 0 .87-1 .42 h at 15 °C, by Marchant& Hynes(1981) and 0 .75-2 .0 h at 17 'C, by Barlocher & Kendrick (1975) . There is no clear evidence of different gut passage times comparing exposed elm leaves and fine detritus .…”

Section: Discussionsupporting

confidence: 66%

Gut passage times in Gammarus pulex (Crustacea, Amphipoda) and aspects of summer feeding in a stony stream

Willoughby

Earnshaw

1982

Hydrobiologia

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Gut passage times in Gammarus pulex (Crustacea, Amphipoda) were calculated by counting and measuring voided faecal pellets . Following feeding on elm leaves conditioned in a stream, or summer fine detritus from the same source, calculated gut passage times were usually short, about 2 h or less at 15 ° C . Using harder oak and beech leaves, not previously conditioned in the stream, apparent gut passage times were much longer, 8-48 h, but since intermittent feeding occurred these figures are not comparable to the others .In connection with summer feeding of the animal in the stream, the microbiological status of the fine detritus there was studied . It contained fungal hyphae, which were mostly empty, viable fungal spores of terrestrial derivation, and bacteria, all largely carried on fragments of vascular plant tissues . In experiments, such fungal spores (of A ureobasidiumpullulans and of Mucor sp .), incorporated into fine detritus, were not digested by the animal . The bacterium Bacillus cereus was present in the fine detritus and when the latter was consumed it survived passage through the gut of the animal . Using B. cereus as a proportion marker it was concluded that other unicellular bacteria in the fine detritus were not digested either . In other experiments, not immediately related to the summer season, nutrient extraction by the animal from hyphae of the fungus Nectria lugdunensis was examined ; it probably occurs through sub-microscopic pores connecting the cells . This mode of extraction may apply when the animal consumes vascular plant tissues .

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Section: Discussionsupporting

confidence: 66%

Gut passage times in Gammarus pulex (Crustacea, Amphipoda) and aspects of summer feeding in a stony stream

Willoughby

Earnshaw

1982

Hydrobiologia

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“…S8). However, as the nutritional value of microbial cells is four to ten times higher than that of unconditioned leaf material [15] and fungi usually contribute more than 85% to the microbial biomass on decaying leaves [34], the reduced fungal biomass alone indicates a substantially lower nutritional value of the leaf material in the tebuconazole treatment. Thus, Gammarus is possibly also forced to compensate, besides the direct toxic effects, the nutritional deficiency by an increase in assimilation (i.e., postingestive compensation) [35].…”

Section: Resultsmentioning

confidence: 99%

“…Thereafter, filters were dried and weighed as described above to determine feces production of each animal. During the first week of the present study, feces production was not assessed because feces may have originated from food different than that provided during the bioassay [15]. Accordingly, from week two onward, three additional replicates per treatment were set up without animals to correct for increases in filter weight due to microbial decomposition of leaf material.…”

Section: Bioassaymentioning

confidence: 99%

Ecotoxicological impact of the fungicide tebuconazole on an aquatic decomposer‐detritivore system

Zubrod

Bundschuh

Feckler

et al. 2011

Enviro Toxic and Chemistry

103

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Leaf litter breakdown is a fundamental process in aquatic ecosystems that is realized by microbial decomposers and invertebrate detritivores. Although this process may be adversely affected by fungicides, among other factors, no test design exists to assess combined effects on such decomposer-detritivore systems. Hence, the present study assessed effects of the model fungicide tebuconazole (65 µg/L) on the conditioning of leaf material (by characterizing the associated microbial community) as well as the combined effects (i.e., direct toxicity and food quality-related effects (=indirect)) on the energy processing of the leaf-shredding amphipod Gammarus fossarum using a five-week semistatic test design. Gammarids exposed to tebuconazole produced significantly less feces (≈ 20%), which in turn significantly increased their assimilation (≈ 30%). Moreover, a significantly reduced lipid content (≈ 20%) indicated lower physiological fitness. The conditioning process was altered as well, which was indicated by a significantly reduced fungal biomass (≈ 40%) and sporulation (≈ 30%) associated with the leaf material. These results suggest that tebuconazole affects both components of the investigated decomposer-detritivore system. However, adverse effects on the level of detritivores cannot be explicitly attributed to direct or indirect pathways. Nevertheless, as the endpoints assessed are directly related to leaf litter breakdown and associated energy transfer processes, the protectiveness of environmental risk assessment for this ecosystem function may be more realistically assessed in future studies by using this or comparable test designs.

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“…We used the following assimilation efficiencies for invertebrate consumers: diatoms, 0.3; amorphous detritus, 0.1; leaf litter, 0.1; filamentous algae, 0.3; macrophytes, 0.1; fungi, 0.7; and animal material, 0.7 (Ba¨rlocher and Kendrick 1975, Benke and Wallace 1980, 1997. NPE of invertebrates was assumed to be 0.5.…”

mentioning

confidence: 99%

Food‐web dynamics in a large river discontinuum

Cross

Baxter

Rosi‐Marshall

et al. 2013

Ecological Monographs

162

194

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Abstract. Nearly all ecosystems have been altered by human activities, and most communities are now composed of interacting species that have not co-evolved. These changes may modify species interactions, energy and material flows, and food-web stability. Although structural changes to ecosystems have been widely reported, few studies have linked such changes to dynamic food-web attributes and patterns of energy flow. Moreover, there have been few tests of food-web stability theory in highly disturbed and intensely managed freshwater ecosystems. Such synthetic approaches are needed for predicting the future trajectory of ecosystems, including how they may respond to natural or anthropogenic perturbations.We constructed flow food webs at six locations along a 386-km segment of the Colorado River in Grand Canyon (Arizona, USA) for three years. We characterized food-web structure and production, trophic basis of production, energy efficiencies, and interaction-strength distributions across a spatial gradient of perturbation (i.e., distance from Glen Canyon Dam), as well as before and after an experimental flood. We found strong longitudinal patterns in food-web characteristics that strongly correlated with the spatial position of large tributaries. Above tributaries, food webs were dominated by nonnative New Zealand mudsnails (62% of production) and nonnative rainbow trout (100% of fish production). The simple structure of these food webs led to few dominant energy pathways (diatoms to few invertebrate taxa to rainbow trout), large energy inefficiencies (i.e., ,20% of invertebrate production consumed by fishes), and right-skewed interaction-strength distributions, consistent with theoretical instability.Below large tributaries, invertebrate production declined ;18-fold, while fish production remained similar to upstream sites and comprised predominately native taxa (80-100% of production). Sites below large tributaries had increasingly reticulate and detritus-based food webs with a higher prevalence of omnivory, as well as interaction strength distributions more typical of theoretically stable food webs (i.e., nearly twofold higher proportion of weak interactions). Consistent with theory, downstream food webs were less responsive to the experimental flood than sites closest to the dam. We show how human-induced shifts to foodweb structure can affect energy flow and interaction strengths, and we show that these changes have consequences for food-web function and response to perturbations.

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Assimilation Efficiency of Gammarus pseudolimnaeus (Amphipoda) Feeding on Fungal Mycelium or Autumn-Shed Leaves

Cited by 122 publications

References 18 publications

Gut passage times in Gammarus pulex (Crustacea, Amphipoda) and aspects of summer feeding in a stony stream

Gut passage times in Gammarus pulex (Crustacea, Amphipoda) and aspects of summer feeding in a stony stream

Ecotoxicological impact of the fungicide tebuconazole on an aquatic decomposer‐detritivore system

Food‐web dynamics in a large river discontinuum

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