Faecal pellets in streams: their binding, breakdown and utilization

1. Faecal pellets of Gammarus (shredders) and Simulium larvae (suspension feeders) are bound by exopolymers. Immediately after egestion, Gammarus pellets are covered by a peritrophic membrane that breaks up within hours, although pellets remain intact because of internal binding materials. 2. Although they expand soon after egestion, the faecal pellets of Gammarus and Simulium remain intact for more than 30 days. Their internal structure is altered and the main agents of this change are bacteria that have survived passage through the gut (and become bound within pellets). 3. When disrupted physically, freshly egested (1‐ to 2‐day old) Simulium faecal pellets break up into relatively large pieces whereas freshly egested Gammarus faecal pellets break apart into much smaller pieces. Disruption of 30‐day old Simulium faecal pellets results in similar sized pieces to those from freshly egested pellets, but disruption of 30‐day old Gammarus pellets produces pieces that are two orders of magnitude larger than those resulting from disruption of freshly egested pellets. 4. Faecal pellets of Gammarus and Simulium are eaten by stream invertebrates and are sites of microbial breakdown. Faecal pellets are a source of organic matter for benthic invertebrates, bacteria and, indirectly, for plants.     

Is sedimentation of copepod faecal pellets determined by cyclopoids? Evidence from enclosed ecosystems

Vertical flux of faecal pellets was compared in 26 verticallystratified 27 m³ (diameter 2 m, depth 9.3 m) in situ seawaterenclosures deriving from four separate experiments on the Norwegianwest coast. Sediment traps were mounted in the non-mixed lowerlayer at 8 m depth. The zooplankton community composition wasnatural in three of the experiments, while manipulated to includefour concentrations of Calanus finmarchicus in one. Calanoidcopepods such as C. finmarchicus, Paracalanus spp., Pseudocalanusspp. and Microcalanus spp. dominated the zooplankton biomassin all mesocosms, except in eight of the enclosures where thecyclopoid copepod Oithona spp. occupied up to 40% of the biomass.Vertical flux of faecal pellet carbon (FPC) showed a significantnegative correlation with Oithona biomass. In order to determinethe retention potential of Oithona, measured sedimented faecalpellet carbon (FPC_sed) was compared with estimated maximum andminimum egestion rates. FPC_sed decreased with increased biomassof Oithona. When the contribution of Oithona to the total copepodbiomass was high, FPC_sed was reduced to a few per cent of themaximum calanoid egestion rate (E_max) and was significantlyless than the expected minimum calanoid egestion rate (E_min)in four of the mesocosms. On the other hand, FPC_sed increasedtowards E_max when the fraction of calanoid copepods increasedtowards 100% of the total copepod biomass. The results wereobtained in experiments characterized by an extensive rangeof physical and biological processes. We suggest that the biomassratio between pellet-producing (calanoids) and pellet-reworkingcopepods (Oithona) may be used to predict relative pellet retentionand/or sedimentation rates of calanoid faecal pellets in naturalplankton.     

Rapid species identification of pygmy rabbits (Brachylagus idahoensis) from faecal pellet DNA

The pygmy rabbit (Brachylagus idahoensis) is a small lagomorph of the western United States that specializes in sagebrush (Artemisia spp.) habitat. Intensive habitat loss and modification have increased the vulnerability of pygmy rabbit populations, but the current geographic distribution and population status remain unclear. To aid in detection and population monitoring, we developed a species identification test that uses mitochondrial DNA species-specific primers to distinguish among six sympatric lagomorph species using DNA isolated from faecal pellets. Applying this test, we successfully identified the species of origin for all pellet samples that produced a positive PCR result (77% of 283 pellets collected). Pellets collected during the winter (December-February) had higher PCR success rate (93%) than pellets collected at other times of the year (72%). This test, using non-invasive genetic sampling of faecal pellets, provides an efficient method for assessing site occupancy and distribution of pygmy rabbits and other lagomorphs across large geographic areas.     

Periphyton responds differentially to nutrients recycled in dissolved or faecal pellet form by the snail grazer Theodoxus fluviatilis

1. We aimed to separate the effects of grazers on periphyton via grazing from that of nutrient recycling from their faecal pellets. 2. We set up three different experimental treatments (snails/no snails/faecal pellets) and sampled over 16 days. The ‘snail’ treatment contained a low density (snail biomass c. 14 g^?2) of the gastropod grazer Theodoxus fluviatilis and the ‘faecal pellet’ treatment received the same amount of faecal pellets as were produced in the ‘snail’ treatment. Whereas the ‘faecal pellet’ treatment provided extra nutrients to periphyton from the faeces, the ‘snail’ treatment provided nutrients in the form of both faeces and in excreta. There was also direct grazing on periphyton in the ‘snail’ treatment. The ‘no snail’ was not grazed and received no nutrients in faeces or excreta. 3. We measured periphyton C, N and P content, chlorophyll‐a (chl‐a), primary production, bacterial biomass, bacterial production and bacterial respiratory activity. In the water column we measured dissolved inorganic N and soluble reactive P. 4. Snails increased the amount of dissolved inorganic N in the water. On day 16, the periphyton N : P ratio in the ‘faecal pellet’ treatment was lower, and periphyton P content was higher, than in the other two treatments. N : P ratios decreased over time in the ‘faecal pellet’ treatment. Primary and bacterial production were positively correlated in all treatments. 5. Algal chl‐a and primary production of periphyton per unit area and periphyton chl‐a : C ratios increased over the 16 day in the ‘snail’ treatment, and thus excretion of dissolved N by snails had a stronger positive effect on the periphyton community than N and P in faecal pellets. 6. Our data show that excretion and egestion can have different effects on periphyton, probably because of the higher proportion of dissolved N in excreta and the higher proportion of P recycled in faecal pellets. The relative effect of nutrients recycled in egesta or in excretions, probably depends on the form of nutrient limitation of the periphyton. Further, the different components of the periphyton matrix could react differently to the different forms of nutrient recycling. 7. We conclude that direct grazing effects are less important than nutrient effects when nutrients are limiting and grazing pressure is low. Further, the spatial separation of different grazing effects can lead to differences in periphyton production and nutrient stoichiometry. This might be an explanation for the patchiness of periphyton in nature.     

Contrasting effects of functionally distinct tadpole species on nutrient cycling and litter breakdown in a tropical rainforest stream

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棉铃虫围食膜的蛋白质组鉴定

【目的】围食膜(peritrophic membrane, PM)是昆虫抵御随食物摄入的病原微生物入侵的第一道天然屏障。本研究旨在鉴定出农业重大害虫棉铃虫Helicoverpa armigera围食膜的总蛋白成分,为进一步揭示昆虫围食膜的形成机制及研发新颖的害虫控制策略奠定基础。【方法】剥离棉铃虫5龄幼虫PM,用三氟甲磺酸(trifluoromethane sulfonic acid, TFMS)处理,采用液质联用技术(LC-MS/MS)鉴定围食膜蛋白质组,然后对鉴定结果进行生物信息学分析。【结果】本研究共鉴定出棉铃虫幼虫围食膜蛋白质169个,是目前鉴定最多的棉铃虫围食膜蛋白。通过GO分析,可以将这些鉴定的蛋白分为细胞组分、分子功能和生物学过程三大类;KEGG富集结果显示,鉴定蛋白可以富集在12条代谢通路中;蛋白互作分析(protein protein interaction, PPI)结果表明,以ACC和CG3011等蛋白为核心可以形成蛋白互作网络。【结论】本研究鉴定了169个棉铃虫幼虫围食膜蛋白质,并对其进行了GO, KEGG和PPI分析,结果有助于人们全面理解昆虫围食膜的分子结构和功能。     

Visual observations on the process of digestion and the production of faecal pellets in the chaetognath Sagitta hispida Conant

The passage of food through the gut of Sagitta hispida Conant is described as a batch process and the formation of membranes which surround the faecal material is demonstrated photographically. The utility of such a peritrophic membrane system is considered in the light of the marine ecosystem as a whole.     

Abundance and germination capability of resting cysts of Alexandrium spp. (Dinophyceae) from faecal pellets of macrobenthic organisms

The Alexandrium spp. resting cysts were found abundantly in faecal pellets collected from the bottom sediments at two stations in Hiroshima Bay. It is considered that these faecal pellets were excreted by the macrobenthos, such as polychaeta and mollusca, based on their size and morphology. Polychaeta was the most dominant macrobenthos, and mollusca was the second most dominant group in Hiroshima Bay. The resting cysts of Alexandrium spp. in the bottom sediments at the two stations were counted in both the faecal pellets of macrobenthos and in the surrounding sediment. As a result, the number of cysts in the faecal pellets accounted for 28.9-35.2% of total cysts. In addition, cysts isolated from faecal pellets had almost the same germination ability as those in the sediment. Thus, Alexandrium cysts are tolerant to the predation and digestive processes of macrobenthic organisms.     

Leader of the pack: faecal pellet deposition order impacts PCR amplification in wombats

DNA sourced from faeces is notoriously less reliable than that from tissue. Hence, understanding whether faecal pellet quality varies within faecal piles may be important for sample selection. We hypothesized that the order in which faecal pellets are deposited may influence microsatellite polymerase chain reaction (PCR) amplification success from sampled faeces, more specifically, that first pellets deposited will have signatures of greater success than later ones. In a first test of the hypothesis, first and later-deposited pellets, as determined from the direction of footprints, were collected from fresh (overnight) faecal piles of northern hairy-nosed wombats (Lasiorhinus krefftii). DNA extracts were typed for seven microsatellite loci. We found that faecal deposition order significantly affected optical density of bands on autoradiographs (a measure of PCR amplification success) when the first faecal pellet was compared with the last one, but not when the first pellet was only distinguishable from later ones. The absence of a difference in amplification rate between first and later pellets is likely a reflection of the overall high amplification success in this study. That first pellets deposited yield more product suggests they contain more intestinal cells. Although further comparisons are needed, these results may inform sample selection in species for which success of microsatellite PCR amplification of faecal DNA is low. Deposition order may have more of an impact on amplification success and genotyping errors as faecal age increases.     

The peritrophic membrane as a barrier: its penetration by Plasmodium gallinaceum and the effect of a monoclonal antibody to ookinetes

We studied the point at which a monoclonal antibody (mAb C5) to a surface protein (Pgs25) on Plasmodium gallinaceum ookinetes blocked the infection of Aedes aegypti mosquitoes. The antibody did not block the development of zygotes to ookinetes in vitro. Development of ookinetes to oocysts in the mosquito was blocked to the same extent whether zygotes grew to ookinetes in the presence of mAb C5 or the antibody was added after the ookinetes had reached full development. When ookinetes developed in vitro in the presence of mAb C5, antibody remained on the surface of the parasite for the next 50 hr and did not block attachment to the peritrophic membrane. When ookinetes were fed to mosquitoes, two subpopulations of mosquitoes were observed (high numbers of oocysts per midgut and low numbers of oocysts per midgut). mAb C5 reduced the number of oocysts per midgut in the subpopulation that had low numbers of oocysts. The subpopulation that had high numbers of oocysts was unaffected by antibody, indicating that the antibody did not block invasion of the midgut epithelium. When mAb C5 was fed with gametocytes, the parasites invaded the epithelium at the same time (between 30 and 35 hr after the blood meal) as in controls, although at a markedly reduced rate. The ultrastructural observations were consistent with a block of parasites within the peritrophic membrane and not with a block at the epithelium, as parasites were not seen to accumulate within the space between the peritrophic membrane and the epithelium. The mechanism by which mAb C5 to Pgs25 of P. gallinaceum blocks the penetration of the peritrophic membrane remains undefined. We present evidence that the parasite modifies the peritrophic membrane during penetration, an observation first made for Babesia microti during penetration of the peritrophic membrane in Ixodes ticks. Ookinetes in the absence of antibodies appeared to disrupt the layers of the peritrophic membrane, suggesting an enzymatic mechanism for penetration.     

Infectivity of Hymenolepis nana eggs from faecal pellets in the rectum of mice

The infectivity of Hymenolepis nana eggs from faecal pellets in the rectum of mice was compared with that of the eggs in gravid proglottids of adult H. nana and with that of the eggs in excreted faecal pellets to find out a simple method for collecting H. nana eggs of high infectivity to mice. Eggs from faecal pellets in the rectum showed higher infectivity than those from gravid proglottids and as high infectivity as those from gravid proglottids selected by a watch-glass rotation technique. Eggs in faecal pellets in the rectum did not lose infectivity until 4 h after they were excreted and exposed to the air at room temperature (27-28 degrees C) with relative humidity of 35-40%. However, the eggs lost infectivity significantly 17 h after excretion onwards.     

Iberian Rock Lizards (Lacerta monticola cyreni) Assess Conspecific Information Using Composite Signals from Faecal Pellets

A field and laboratory study was performed to analyse the role of excrement deposited on the substrate in intraspecific communication of the Iberian rock-lizard (Lacerta monticola cyreni). In the field, lizards selected specific sites on rocks to deposit faecal pellets, probably in order to facilitate visual location of pellets by conspecifics. Differential tongue flick rates to chemicals presented on cotton swabs demonstrated that male lizards can detect and discriminate between self-produced scents from faecal pellets and those of other conspecific males. In a subsequent experiment, male lizards were tested in a chamber with two platforms containing a faecal pellet of other male on one side and a control artificial pellet on the opposite side. Males spent significantly less time on the side containing the faecal pellet, suggesting that the decision of where to stay may depend on the presence of faecal pellets. Smaller males moved less than larger males on the experimental side whereas on the control side body size did not influence the proportion of time moving. The ability to discriminate chemicals from faeces, and the effects of faecal pellets on lizard behaviour, suggests that faeces might act as composite signals (visual and chemical) in the intraspecific communication of this lizard.     

Chitin in the peritrophic membrane of Acarus siro (Acari: Acaridae) as a target for novel acaricides

The peritrophic membrane in Acarus siro L. (Acari: Acaridae) is produced by distinct cells located in the ventriculus. In this study, the chitin inside the peritrophic membrane was detected using wheat germ-lectin conjugated with colloidal gold (10 nm). The chitin fibrils of the peritrophic membrane were a target for chitin effectors, including 1) chitinase, which hydrolyzes chitin fibers inside the peritrophic membrane; 2) calcofluor, which binds to chitin and destroys the peritrophic membrane mesh structure; and 3) diflubenzuron, which inhibits chitin synthesis. In addition, soybean trypsin protease inhibitor (STI) and cocktails of chitinase/calcofluor, diflubenzuron/calcofluor and chitinase/STI were tested. These compounds were supplemented in diets and an increase of population initiated from 50 individuals was observed after 21 d of cultivation. Final A. siro densities on experimental and control diets were compared. The chitin in the peritrophic membrane was determined to be a suitable target for novel acaricidal compounds for suppressing the population growth of A. siro. The most effective compounds were calcofluor and diflubenzuron, whereas the suppressive effects of chitinase and STI were low. The failure of chitinase could be due to its degradation by endogenous proteases. The combination of chitinase and STI suppressed A. siro population growth more effectively than when they were tested in oral admission separately. The combinations of calcofluor/chitinase or calcofluor/difluorbenzuron showed no additive effects on final A. siro density. The presence of chitin in peritrophic membrane provides a target for novel acaricidal compounds, which disrupt peritrophic membrane structure. The suitability of chitin effectors and their practical application in the management of stored product mites is discussed.     

Diet of the golden-tipped bat Kerivoula papuensis (Microchiroptera) from north-eastern New South Wales, Australia

The diet of the golden-tipped bat ( Kerivoula papuensis ) was investigated by collecting faecal samples from captured individuals in the Richmond Range State Forest, north-eastern New South Wales, Australia. Faecal analysis was used so that all captured individuals could be released after processing and banding. A total of 53 faecal pellets were collected in the summer and autumn months from 39 individuals. The major food of K. papuensis were spiders (Araneida) comprising 91.9% of the total volume of food. Other foods consumed in small quantities were Coleoptera, Lepidoptera and Diptera.     

Vertical distribution of faecal pellets during FLEX '76

During FLEX '76 (Fladen Ground Experiment), the vertical distribution of faecal pellets was studied at a time station on the Fladen Ground (North Sea). Generally, the faecal pellets showed a clearly-defined maximum above the main thermocline within a depth of 0–30 m. Only in a period of storms was the faeces-maximum lowered to the main thermocline, which occurred at 50–60 m depth. The maximum numbers of the copepodCalanus finmarchicus, the most important producer of faecal pellets, initially occupied the same level as the faeces maximum. However, from the middle of May, theC. finmarchicus population started a diel vertical migration, during which, as a rule, the copepods migrated away from the surface region into deeper waters. On this occasion, the faecal pellet maximum did not break up but remained in the uppermost layer of the water column. The high concentrations of faecal pellets found within the uppermost 30 m of the water column contradict the extremely high sinking rates of faeces reported by various authors. The quotients of the depth-integrated counts of faecal pellets andC. finmarchicus individuals were calculated. The main maximum of faeces per individual occurred in the period between 28 April and 6 May 1976. A second, smaller maximum was documented between 23–28 May 1976. These two maxima coincided with the development of phytoplankton blooms observed at this particular time station.JONSDAP '76 Contribution No. 68.     

Salt-marsh Crustaceans, Gammarus duebeni and Palaemonetes varians as Predators of Mosquito Larvae and Their Reaction to Bacillus thuringiensis subsp. israelensis

The predatory potential of two onmnivorous crustaceans, Gammarus duebeni and Palaemonetes varians, has been examined to investigate their effect as mosquito larval predators. Mature gammarids ate 4-8 Aedes detritus larvae/24 h and palaemonids, 22-30/1 h, often killing larvae when not hungry. The crustaceans were exposed to Bacillus thuringiensis subsp. israelensis (Bti) and to mosquito larvae killed by Bti with no adverse effects, endorsing the safety of this microbial pesticide. Crustacean faecal pellets, collected post-feeding and placed in fresh marsh water, were toxic to mosquito larvae the following day. After placing the crustaceans in fresh salt-marsh water for 6 days, the fresh faecal pellets failed to kill mosquitoes apart from pellets obtained from crustaceans originally fed on the highest concentration of Bti, where there was a 50% kill after 3 days of incubation. Mosquito larvae on salt-marshes are not easy to control with ecologically undesirable toxic chemicals. Encouraging the breeding of predators such as crustaceans, or even their release, could prove to be a useful method of mosquito control to supplement the periodic inundative use of the ecologically acceptable Bti.     

Evidence for a sugar receptor (lectin) in the peritrophic membrane of the blowfly larva, Calliphora erythrocephala Mg. (Diptera)

For the first time a sugar receptor (lectin) has been localized by electron microscopy in an invertebrate. The peritrophic membrane of the blowfly larva, Calliphora erythrocephala, is shown here to express lectins with high specificity for mannose. The lectin is restricted to the lumen side of the peritrophic membrane. The surface of the midgut epithelium is devoid of mannose-specific lectins. It is suggested that the midgut epithelium has lost these lectins during the course of evolution in favour of the peritrophic membrane which is secreted by specialized cells only at the beginning of the midgut.Peritrophic membranes and the midgut epithelium lack lectins specific for galactose. The lumen side of the peritrophic membrane of the larvae has mannose and/or glucose residues, and it is densely packed with two species of bacteria, Proteus vulgaris and P. morganii. These also have mannose-specific lectins as well as mannose residues on their pili. The existence of mannose-specific receptors and mannose residues on both, peritrophic membranes and bacteria, leads to the assumption of mutual adherence between the two surfaces.     

Organic matter processing by chironomid larvae (Diptera: Chironomidae)

In laboratory experiments, we used fluorescent dye markers to investigate processing of organic matter by larvae of Psectrocladius limbatellus (Holm.) (Diptera: Chironomidae). 59% of the organic matter used was incorporated into tubes, 39% was present in faecal pellets (both after 24 h), and 2% was found in the larval gut at the end of experiments. Ingested matter passed through the gut rapidly, resulting in the gut being emptied more than 20 times each day. Further 24-h experiments using dye-marked faecal pellets showed that 6% of pellets produced were re-ingested and 12% were incorporated into tubes. There was no preference for conditioned faecal pellets as food over those that had recently been egested and tubes also provided a food reserve on which larvae feed. Chironomid larvae recycle organic matter resulting in its mineralization and their ‘engineering’ has a dramatic effect on the substratum. This revised version was published online in July 2006 with corrections to the Cover Date.     

Changes in microbial biomass,respiration and nutrient status of beech (Fagus sylvatica) leaf litter processed by millipedes (Glomeris marginata)

The effect of processing of beech leaf litter (Fagus sylvatica L.) of different ages by the diplopodGlomeris marginata (Villers) on status and turnover of microorganisms was investigated in the laboratory. Microbial biomass, basal respiration and metabolic quotient of litter-material from three different beechwood sites of a basalt hill forming a gradient from basalt (upper part of the hill) to limestone (lower part of the hill) were determined each season (February, May, August and November). The same microbial parameters were also measured after these litter materials had been processed byG. marginata (faecal pellets of an average age of 4 days). Short-term changes in microbial biomass and respiration in leaf material and faecal pellets from February and August were investigated after 1, 2, 5, 10, 20 and 40 days of incubation. The ergosterol content of August samples was determined. Processing of beech leaf litter byG. marginata increased microbial biomass in February and May but reduced microbial biomass in August and November. It was concluded that processing of litter materials in February and May increased accessibility of carbon resources to microorganisms by fragmentation. In contrast, in litter materials from August and November carbon resources were depleted and fragmentation by diplopods did not increase availability of carbon resources. Addition of carbon (glucose) and nutrients (nitrogen and phosphorus) to litter and faecal pellets indicated that processing of beech litter reduced nutrient deficiency of the microflora. Ergosterol content in faecal pellets was reduced strongly after beech leaf litter processing byG. marginata, indicating a decrease in fungal biomass. Presumably, in faecal pellets bacteria flourished at the expense of fungi.     

FAECAL PRODUCTION AND AN ESTIMATE OF FOOD INTAKE IN THE WILD OF THE ANTARCTIC LIMPET NACELLA CONCINNA (STREBEL)

The Antarctic limpet Nacella concinna is common in shallow watersaround the Antarctic Peninsula, and has a mean density of 125individuals/m² at Signy Island (Picken, 1980). In the australsummer 1986/87 ammonia excretion and faecal egestion were measuredas part of a programme to develop a detailed individual energybudget for this species. Ammonia production was measured in 102 individuals ranging from3 to 720 mg dry weight. For a standard limpet of 200 mg dryweight, ammonia excretion was 0.13 µg-at/hr. Comparedwith previous measures of oxygen uptake these data suggest anO:N atomic ratio of between 15 and 25. The relationship betweenammonia excretion and dry weight could be expressed by a powercurve with a weight exponent of 0.82 (SE 0.042). Faecal production was measured in limpets freshly sampled fromthe field, and placed in dean seawater for 4 days. During thistime faecal production decreased (since the limpets were notfeeding), although only data from the first 24 hours were used.Again the relationship between faecal egestion and dry weightcould be expressed by a power curve, although this time theweight exponent was 0.94 (SE 0.101). The ash content of thefaecal strings increased significantly with the size of thelimpet, possibly because larger limpets were ingesting a greaterproportion of substrate during feeding. If this is so, thenthis would also explain the weight exponent dose to 1.0, ratherthan the value of about 0.8 to be expected from metabolic measures(since larger limpets would be passing relatively more faecalmaterial). If assimilation efficiency is known, then food intake in thewild may be estimated from a measurement of faecal egestionand faecal organic content (Clarke et at., 1988). Applying typicalvalues of assimilation efficiency for limpets (40 to 60%) suggestsa daily food intake in Nacella of 2 to 3% body weight per day.This is a quite typical figure for a grazing limpet, and suggeststhere is no resource limitation for Nacella at Signy in summer.