Home  About us  Contact
 

Experiments Testing (experiment + testing)

Distribution by Scientific Domains
Life Sciences100%

Selected Abstracts

Sensory Systems and Spatial Memory in the Fruit Bat Rousettus aegyptiacus

ETHOLOGY, Issue 8 2005
Richard A. Holland
The megachiropteran fruit bat Rousettus aegyptiacus is able to orient and navigate using both vision and echolocation. These two sensory systems have different environmental constraints however, echolocation being relatively short range when compared with vision. Despite this difference, an experiment testing their memory of a perch location demonstrates that once the location of a perch is learned R. aegyptiacus is not influenced by the movement of local landmark cues in the vicinity of the perch under either light or dark conditions. Thus despite the differing constraints of vision and echolocation, this suggests a place is remembered as a location in space and not by associations with landmarks in the vicinity. A decrease in initial performance when the task was repeated in the dark suggested the possibility that a memory of a location learned using vision does not generalize to echolocation. [source]

A model predicting waterborne cadmium bioaccumulation in Gammarus pulex: The effects of dissolved organic ligands, calcium, and temperature

ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 11 2009
Bastien Pellet
Abstract Metal bioavailability depends on the presence of organic ligands in the water and on the concentrations of competitive cations. The present study aims at testing whether the diffusive gradient in thin films technique (DGT) could be used to take into account Cd speciation and its consequences on bioavailability in a bioaccumulation model and whether the influences of the Ca concentration and temperature also should be considered. Four kinetic experiments were conducted on Gammarus pulex: a calibration of Cd turnover rates and of the DGT lability in mineral water, a study of the influence of ethylenediaminetetraacetic acid (EDTA) and humic acids (HA) on uptake rates, and two experiments testing the influence of the Ca concentrations and temperature on Cd uptake clearance rates (ku). In mineral water, where Cd was considered fully labile, the ku was 0.46 L g,1 d,1, and the depuration rate was 0.032 d,1. The initial Cd influxes were lowered significantly by additions of 10 ,g L,1 of EDTA or 10 mg L,1 of HA in the water but not at 5 mg L,1 HA, even if DGT measurements proved that Cd formed Cd,HA complexes in that treatment. Increasing Ca concentrations lowered ku values, and a competitive inhibition model between Ca and Cd fitted the data. A 30% enhancement of ku values was observed when the temperature was increased by 8°C, which appeared comparatively as a weak effect. Thus, taking into account the metal speciation and the influence of the Ca concentration should improve Cd bioaccumulation modeling in amphipods. In freshwater, where metal bioavailability is reduced by the presence of dissolved organic matter, forecasting Cd waterborne uptake using the labile concentrations should allow robust comparisons between laboratory and field studies. [source]

Field experiments testing for apparent competition between primary parasitoids mediated by secondary parasitoids

JOURNAL OF ANIMAL ECOLOGY, Issue 2 2001
Rebecca J. Morris
Summary 1,Two field manipulation experiments were performed to look for apparent competition between primary parasitoids of aphids, mediated by shared secondary parasitoids. In each case the frequency of secondary parasitism on a ,focal' species was compared in the presence or absence of a ,treatment' species and its aphid host. 2,In both experiments the focal species was Aphidius ervi (Haliday) attacking Acyrthosiphon pisum (Harris) (pea aphid). In the first experiment the treatment species was Aphidius rhopalosiphi (De Stefani-Perez) attacking Sitobion avenae (Fabricius) (a grass aphid) and in the second Aphidius microlophii (Pennachio & Tremblay) attacking Microlophium carnosum (Buckton) (nettle aphid). 3,No significant effects of either the presence of A. rhopalosiphi or of its host on secondary parasitism of A. ervi were detected in the first experiment. 4,In the second experiment, rates of secondary parasitism were estimated twice: a significant effect of treatment was found on the first occasion but not the second. In the former, parasitism was highest in the presence of the treatment species and its host, intermediate when just the host was present, and lowest when both were absent. 5,We discuss the evidence for apparent competition in host-parasitoid communities. [source]

Beehive fence deters crop-raiding elephants

AFRICAN JOURNAL OF ECOLOGY, Issue 2 2009
Lucy E. King
Abstract Previous work has shown that African elephants Loxodonta africana will avoid African honeybees Apis mellifera scutellata. Here we present results from a pilot study conducted to evaluate the concept of using beehives to mitigate elephant crop depredation. In Laikipia, Kenya, we deployed a 90-m fence-line of nine inter-connected hives, all empty, on two exposed sides of a square two-acre farm that was experiencing high levels of elephant crop depredation. Compared with a nearby control farm of similar status and size, our experimental farm experienced fewer raids and consequently had higher productivity. Socioeconomic indicators suggest that not only was the concept of a beehive fence popular and desired by the community but also that it can pay for its construction costs through the sale of honey and bee products. We are calling for experiments testing this concept of a ,guardian beehive-fence' to be conducted rigorously and scientifically in as wide a range of agricultural settings as possible to evaluate jointly its effectiveness and efficiency. Résumé Des travaux antérieurs ont montré que les éléphants africains Loxodonta africanaévitent les abeilles africaines Apis mellifera scutellata. Nous présentons ici les résultats d'une étude pilote réalisée pour évaluer le concept consistant à utiliser des ruches pour réduire la destruction des cultures par les éléphants. A Laikipia, au Kenya, nous avons installé une barrière de 90 m. de long composée de neuf ruches interconnectées, toutes vides, sur deux côtés exposés d'une ferme carrée de deux acres (arpents) dont les cultures subissaient une forte déprédation causée par les éléphants. Comparée à une ferme contrôle voisine, de statut et de taille comparables, notre ferme expérimentale a subi moins de raids et a donc eu une meilleure productivité. Des indicateurs socioéconomiques suggèrent que non seulement le concept de barrière en ruches était populaire et souhaité par la communauté, mais qu'il peut même couvrir les frais de sa propre construction grâce à la vente de miel et autres produits dérivés. Nous sollicitons que des expériences soient faites pour tester ce concept de « clôture en ruches » de façon rigoureuse et scientifique, dans une gamme aussi étendue que possible d'installations agricoles, afin d'évaluer son efficacité et sa faisabilité. [source]