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Selective Feeding (selective + feeding)
Selected AbstractsThe importance of meiofauna to lotic ecosystem functioningFRESHWATER BIOLOGY, Issue 1 2000Christine C. Hakenkamp Summary 1Although meiofauna occur in large numbers in many streams, almost nothing is known about their functional role. 2In other systems, meiofauna influence microbial and organic matter dynamics through consumption and bioturbation. Given that these are important processes in streams, meiofauna have the potential to influence lotic function by changing the quality and availability of organic matter as well as the number and biotic activity of benthic microbes. Selective feeding by meiofauna has the potential to alter the availability of nutrients and organic carbon. 3Meiofauna generally contribute only a small amount to metazoan production and biomass in streams, although exceptions occur. Within a stream, the relative importance of meiofauna may reflect whether the temporary or permanent meiofauna dominate the meiobenthos as well as the season when samples are collected. 4We suggest stream conditions (small sediment grain size, restricted interstitial flow) under which meiofauna have the greatest likelihood of influencing stream ecosystem function. 5Important areas for future research include addressing whether meiofauna feed selectively, whether meiofauna are links or sinks for carbon in streams, and whether bioturbation by meiofauna influences stream ecosystem processes in a predictable manner. [source] Selective predation on the broad-toothed rat, Mastacomys fuscus (Rodentia: Muridae), by the introduced red fox, Vulpes vulpes (Carnivora: Canidae), in the Snowy Mountains, AustraliaAUSTRAL ECOLOGY, Issue 4 2002K. Green Abstract Since 1981 there has been debate over whether foxes (Vulpes vulpes Linnaeus) selectively prey on the broad-toothed rat (Mastacomys fuscus Thomas) relative to the bush rat (Rattus fuscipes (Waterhouse)). In the present study, three areas of the argument are examined. (i) In a study of fox diet over 3 years at both alpine and subalpine altitudes, M. fuscus outnumbered R. fuscipes in faecal remains in all seasons, in all years, and at both altitudes. Overall, M. fuscus occurred in scats five times as frequently as did R. fuscipes in the alpine zone and twice as often in the subalpine zone. (ii) Data from population studies of M. fuscus and R. fuscipes showed no evidence that M. fuscus is trap shy; neither the pattern of captures of individuals caught once, twice and so on, nor the proportion of the estimated population of each species captured during trapping sessions was significantly different. (iii) The suitable habitat for M. fuscus within the potential home ranges of foxes contributing to the subalpine fox scat collection constituted approximately 50% of the total area. However, there was no significant difference between the numbers of fox trails encountered in habitat suitable or unsuitable for M. fuscus in 19 paired transects skied in winter, indicating no preferential foraging in either habitat. Selective feeding on M. fuscus was therefore established, but how that choice is exercised was not determined. [source] What do dung beetles eat?ECOLOGICAL ENTOMOLOGY, Issue 6 2007PETER HOLTER Abstract 1.,Most adult coprophagous beetles feed on fresh dung of mammalian herbivores, confining ingestion to small particles with measured maximum diameters from 2,5 to 130 ,m, according to body size and kind of beetle. This study explores benefits and costs of selective feeding in a ,typical' dung beetle with a maximum diameter of ingested particles (MDIP) of 20 ,m. 2.,Examined dung types (from Danish domestic sheep, cattle and horse, and African wild buffalo, white rhino and elephant) contained 76,89% water. Costs of a 20 ,m MDIP were often low, since 69,87% of the total nitrogen in bulk dung other than that of elephant and rhino (40,58%) was available to selective feeders. 3.,Nitrogen concentrations were high , and C/N ratios low , in most types of bulk dung compared with the average food of terrestrial detritivores or herbivores. Exceptions were elephant and rhino dung with low nitrogen concentrations and high C/N ratios. 4.,Estimated C/N ratios of 13,39 in bulk dung (sheep,elephant) were decreased by selective feeding to 7.3,12.6 in the ingested material. In assimilated food, ratios are probably only 5,7, as most assimilable nitrogen and carbon may be of microbial origin. If so, the assimilable food contains a surplus of nitrogen relative to carbon. 5.,The primary advantage of selective feeding, particularly in dung with a high C/N ratio, may be to concentrate assimilable carbon in the ingested food. Effects of changing the MDIP within 20,106 ,m are modest, especially in dung with a low C/N ratio. [source] Effects of dietborne copper and silver on reproduction by Ceriodaphnia dubia,ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 1 2009Jason M. Kolts Abstract Recent studies have indicated the potential for dietborne metals as an important exposure pathway for metal toxicity in freshwater organisms. We conducted a study in which freshwater cladocerans (Ceriodaphnia dubia) were fed green algae (either Pseudokirchneriella subcapitata or Chlorella vulgaris) that were grown in Ag- or Cu-contaminated media. In one series of toxicity tests patterned after the U.S. Environmental Protection Agency's three-brood C. dubia chronic toxicity test, we exposed C. dubia to waterborne Ag or Cu while feeding them normal amounts of uncontaminated yeast,Cerophyll®,trout chow (YCT) slurry and either algae grown in standard media or algae grown in standard media supplemented with Ag or Cu (added as AgNO3 or CuSO4·5H2O). These parallel tests demonstrated that dietborne metal did not contribute to survival or reproduction effects beyond the effects caused by waterborne metal alone. We also conducted dietborne-only toxicity tests patterned after two other recently published experimental designs in which 1) C. dubia were fed only metal-contaminated algae for 4 h, transferred to fresh water, and fed uncontaminated algae and YCT slurry for the duration of the three-brood test or 2) C. dubia were fed standard amounts of metal-contaminated algae and uncontaminated YCT slurry for the entire three-brood test. In contrast to previous studies, we did not find consistent dietborne metal toxicity or standard concentration,response relationships in those two experiments. Instead, among-experiment variation in intracellular partitioning of metals in the algae fed to the C. dubia, among-laboratory differences in experimental procedures, selective feeding by C. dubia to avoid metal-contaminated algae, an interaction between reproductive status of the C. dubia and dietborne metal concentration, or a combination of these might help explain the apparently inconsistent results. [source] Contrasting infection frequencies of Neotyphodium endophyte in naturalized Italian ryegrass populations in Japanese farmlandsGRASSLAND SCIENCE, Issue 2 2010Masayuki Yamashita Abstract Neotyphodium endophytes often confer benefits to their host grasses and may enhance invasiveness of some grasses. The knowledge of infection frequencies of endophytes among invading weed populations is necessary to understand the relationships between endophyte infection and invasiveness. Here we present data on infection frequencies of Italian ryegrass (Lolium multiflorum Lam.), an important weed in some farmlands in Japan, persisting in contrasting farmlands: a terraced paddy field and a wheat-soybean double-cropped field in the western region of Shizuoka prefecture, Japan. The terraced paddy site is a mosaic of several landscape elements such as paddy fields, levees, fallow and abandoned fields, with a high percentage of non-crop area. Rice (Oryza sativa L.) has been cultivated for more than a decade with no application of chemical fertilizers, pesticides and fungicides. The wheat-soybean field is characterized by the aggregation of large-scaled fields that were originally reconstructed paddy fields, showing a low percentage of non-crop area. Wheat and soybean have been grown as winter and summer crops, respectively, using chemical fertilizers and herbicides. We examined the presence or absence of endophytes in a total of 1200 seeds sampled from the two Italian ryegrass populations. The terraced paddy population exhibited a markedly high infection frequency (91.0%), due possibly to selective feeding of non-infected seeds by insects. In contrast, the wheat-soybean farmland population showed almost no infection (1.1%), whereas the putative source of the invasion in the proximity exhibited a relatively high infection rate (64.4%). Such a micro-scale variation in infection frequencies may be attributable to a loss in endophyte viability within the wheat-soybean field. The findings suggest that endophyte infection frequency may markedly differ among the Italian ryegrass populations even within the same region, presumably depending on the abundance of the seed-eating insects, farmland management regimes and/or environmental conditions such as soil humidity. [source] The feeding choice of the Red Fox (Vulpes vulpes) in a semi-arid fragmented landscape of North Africa in relation to water and energy contents of preyAFRICAN JOURNAL OF ECOLOGY, Issue 4 2009Graziella L. Dell'Arte Abstract In semi-arid zones, the lack of surface water for drinking forced predators to obtain it from the body fluids of prey and this requires more different prey than that needed to provide energy alone. We examined Red fox (Vulpes vulpes) scats to ascertain if selective feeding compensates the shortage of free water by the ingestion of more prey rich in water such as insects. In addition, we discussed our results in light of increasing habitat fragmentation that, in turn, influences the prey availability. At different spatial levels, recombination of prey assemblages in the diet reaches a solution for variable shortage of water. This was true especially at the landscape level (different degree of aridity) and indirectly for habitat types. Nevertheless, the effects of landscape characteristics probably influenced foxes through the influence of suitable habitats, which partitioned prey species. In fact, increasing values of patchiness had a negative effect on measured energetic gain indices but foxes try to exploiting different patches including small and isolated ones because these surveys become important to obtain water moistures from alternative prey (Orthopters). Résumé Dans les zones semi arides, un manque d'eau de surface à boire a forcé des prédateurs à la trouver dans les fluides corporels de leurs proies, et ceci exige des proies plus diverses que pour la seule production d'énergie. Nous avons examiné des déjections de renard roux (Vulpes vulpes) pour déterminer si une alimentation sélective compense le déficit en eau libre, en ingérant plus de proies riches en eau, tels les insectes. De plus, nous avons discuté nos résultats à la lumière de la fragmentation croissante de l'habitat qui, elle, influence la disponibilité des proies. À différents niveaux spatiaux, la recombinaison d'assemblages de proies dans le régime alimentaire parvient à résoudre une pénurie d'eau variable. Ceci était particulièrement vrai au niveau du paysage (différents degrés d'aridité) et indirectement pour les types d'habitats. Néanmoins, les effets des caractéristiques du paysage ont probablement influencé les renards de par leur influence sur les habitats qui leur sont appropriés, qui divisent les espèces proies. En fait, un morcellement accru avait un effet négatif sur les indices mesurés des gains énergétiques, mais les renards essaient d'exploiter différents sites, y compris les plus petits et les plus isolés, parce que ces incursions deviennent importantes pour trouver l'humidité chez des proies alternatives (orthoptères). [source] | ||||||||||