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

Abstract

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 .

Sex-specific nutrient use and preferential allocation of resources to a sexually selected trait in Hyalella amphipods

“…To compare acquisition among the experimental groups, amphipods (late-stage juveniles: N=16 for both males and females, and adults: N=16 for both males and females) were allowed to feed on the radiolabeled leaves for 2 h [less than average published estimates of gut passage time in amphipods (∼3.5 h, on average); Hargrave, 1970;Neumann et al, 1999;Willoughby and Earnshaw, 1982]. Once the feeding period was over, amphipods were immediately rinsed and transferred to scintillation vials.…”

Characteristics of Lotic Ecosystems and Consequences for Future Research Directions

“…As well as consumers of detritus from the riparian vegetation, grazers oflotic angiosperms must overcome chemical barriers set by plants against grazers elsewhere. (Anderson and Sedell 1979;Willoughby and Earnshaw 1982) microorganisms, especially aquatic hyphomycetes, are viewed as a major link between detritus and shredding consumers. For instance, larval growth of the dipteran Tipula requires fungi and bacteria in the diet, but for reasons other than as a direct source of carbon and nitrogen (Lawson et al 1984).…”

Contribution of fungal biomass to the growth of the shredder, Pycnopsyche gentilis (Trichoptera: Limnephilidae)

“…This idea is supported by the rapid gut passage time exhibited by many detritivores (e.g. <2 h for Gammarus pulex L., Willoughby & Earnshaw, 1982; Welton et al. , 1983) and the refractory nature of plant detritus in comparison to microbial cells (Cummins & Klug, 1979; Maltby, 1992).…”