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Feeding Response (feeding + response)
Selected AbstractsFeeding responses of carabid beetles to dimethoate-contaminated preyAGRICULTURAL AND FOREST ENTOMOLOGY, Issue 2 2004Alice L. Mauchline Abstract 1,The feeding responses of Pterostichus madidus Fab., P. melanarius Illiger and Nebria brevicollis Fab. (Coleoptera: Carabidae) to dimethoate-contaminated prey were investigated in ,no-choice' and ,choice' feeding tests. 2,In the no-choice tests, starved beetles were presented with aphid prey treated with four concentrations of dimethoate. In the choice tests, treated and untreated prey were presented together and the feeding preferences of the starved beetles observed. 3,No avoidance or rejection behaviour was seen in any of the carabids in either of the tests, i.e. no discrimination of the treated and untreated prey was observed. 4,Sufficient dimethoate was consumed with the aphid prey to cause significant mortality levels in the carabids. 5,The concentrations of dimethoate used in these experiments are comparable to field exposure, so carabids feeding in treated fields and field margins could potentially suffer lethal effects via the indirect exposure route of consuming contaminated prey. [source] Behavioural responses of carnivorous marsupials (Planigale maculata) to toxic invasive cane toads (Bufo marinus)AUSTRAL ECOLOGY, Issue 5 2010JOHN LLEWELYN Abstract The arrival of a toxic invasive species may impose selection on local predators to avoid consuming it. Feeding responses may be modified via evolutionary changes to behaviour, or via phenotypic plasticity (e.g. learning, taste aversion). The recent arrival of cane toads (Bufo marinus) in the Northern Territory of Australia induced rapid aversion learning in a predatory marsupial (the common planigale, Planigale maculata). Here, we examine the responses of planigales to cane toads in north-eastern Queensland, where they have been sympatric for over 60 years, to investigate whether planigale responses to cane toads have been modified by long-term exposure. Responses to toads were broadly similar to those documented for toad-naïve predators. Most Queensland planigales seized (21 of 22) and partially consumed (11 of 22) the first toad they were offered, but were likely to ignore toads in subsequent trials. However, unlike their toad-naïve conspecifics from the Northern Territory, the Queensland planigales all survived ingestion of toad tissue without overt ill effects and continued to attack toads in a substantial proportion of subsequent trials. Our data suggest that (i) learning by these small predators is sufficiently rapid and effective that selection on behaviour has been weak; and (ii) physiological tolerance to toad toxins may be higher in planigales after 60 years (approximately 60 generations) of exposure to this toxic prey. [source] Subchronic organismal toxicity, cytotoxicity, genotoxicity, and feeding response of pacific oyster (Crassostrea gigas) to lindane (,-HCH) exposure under experimental conditionsENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 10 2007Gerardo Anguiano Abstract This study evaluated organismal toxicity, cytotoxicity, and genotoxicity and the filtration rate in response to different concentrations of subchronic lindane (gamma-hexachlorocyclohexane [,-HCH]), exposure (12 d) in adult Pacific oysters Crassostrea gigas. Oysters were exposed in vivo in laboratory aquaria to 10 different concentrations (0.0,10.0 mg/L) of ,-HCH. The median lethal concentration (LC50) after 12 d was calculated as 2.22 mg/L. Cytotoxic effects were observed in hemocytes, where the mean cell viability was significantly decreased at 1.0 mg/L of ,-HCH after 12 d. Genotoxicity of ,-HCH measured by single cell gel electrophoresis assay, in hemocytes was evident at 0.7 mg/L of ,-HCH after 12 d. After 4 h of exposure to ,-HCH, filtration rates were reduced compared with controls to 65.8 and 38.2% at concentrations of 0.3 and 0.7 mg/L, respectively, and after 11 d of exposure, filtration rates were reduced to 60.4 and 30.9% at concentrations of 0.1 mg/L and higher. These results show the subchronic effects of ,-HCH at different concentrations and effect sensitivities are categorized as filtration rate < genotoxicity < cytotoxicity < mortality. The relevance of integral toxicity evaluation, considering different endpoints from molecular, cellular, and individual levels is discussed. [source] A short-term sublethal in situ toxicity assay with hediste diversicolor (polychaeta) for estuarine sediments based on postexposure feedingENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 8 2005Susana Maria Moreira Abstract This study evaluated a short-term sublethal endpoint for in situ toxicity assays for estuarine sediments, based on postexposure feeding of the polychaete Hediste (Nereis) diversicolor Müller. A method for precisely quantifying postexposure feeding rates of H. diversicolor was established under laboratory conditions using Artemia franciscana Kellog nauplii. The sensitivity of the postexposure feeding response to copper was investigated by comparing postexposure feeding rates to growth and lethality. The 48-h and 96-h median lethal concentration (LC50) of copper were 241 and 125 ,g/L, respectively, whereas the 48-h median inhibitory concentration (IC50) for postexposure feeding and the 20-d IC50 for growth were 52 and 25 ,g/L of copper, respectively. The influence of different exposure conditions (substrate, temperature, salinity, food availability, and light) on H. diversicolor postexposure feeding was assessed; temperature and salinity were found to influence significantly postexposure feeding. The effectiveness of the proposed in situ assay was investigated by deploying it at two reference and six contaminated Portuguese estuaries. A 48-h exposure period was followed by a 1-h postexposure feeding period. High organism recoveries (89,100%) were obtained. Postexposure feeding was depressed significantly (17,90%) at all contaminated sites relatively to reference sites. The proposed in situ assay with H. diversicolor was shown to be a potential useful tool for estuarine sediment toxicity testing. [source] Learned Recognition of Intraspecific Predators in Larval Long-Toed Salamanders Ambystoma macrodactylumETHOLOGY, Issue 6 2001Erica L. Wildy The ability of prey to detect predators and respond accordingly is critical to their survival. The use of chemical cues by animals in predator detection has been widely documented. In many cases, predator recognition is facilitated by the release of alarm cues from conspecific victims. Alarm cues elicit anti-predator behavior in many species, which can reduce their risk of being attacked. It has been previously demonstrated that adult long-toed salamanders, Ambystoma macrodactylum, exhibit an alarm response to chemical cues from injured conspecifics. However, whether this response exists in the larval stage of this species and whether it is an innate or a learned condition is unknown. In the current study, we examined the alarm response of naïve (i.e. lab-reared) larval long-toed salamanders. We conducted a series of behavioral trials during which we quantified the level of activity and spatial avoidance of hungry and satiated focal larvae to water conditioned by an injured conspecific, a cannibal that had recently been fed a conspecific or a non-cannibal that was recently fed a diet of Tubifex worms. Focal larvae neither reduced their activity nor spatially avoided the area of the stimulus in either treatment when satiated, and exhibited increased activity towards the cannibal stimulus when hungry. We regard this latter behavior as a feeding response. Together these results suggest that an anti-predator response to injured conspecifics and to cannibalistic conspecifics is absent in naïve larvae. Previous studies have shown that experienced wild captured salamanders do show a response to cannibalistic conspecifics. Therefore, we conducted an additional experiment examining whether larvae can learn to exhibit anti-predator behavior in response to cues from cannibalized conspecifics. We exposed larvae to visual, chemical and tactile cues of stimulus animals that were actively foraging on conspecifics (experienced) or a diet of Tubifex (naïve treatment). In subsequent behavioral treatments, experienced larvae significantly reduced their activity compared to naive larvae in response to chemical cues of cannibals that had recently consumed conspecifics. We suggest that this behavior is a response to alarm cues released by consumed conspecifics that may have labeled the cannibal. Furthermore, over time, interactions with cannibals may cause potential prey larvae to learn to avoid cannibals regardless of their recent diet. [source] Growth response of woody species to elephant foraging in Mwea National Reserve, KenyaAFRICAN JOURNAL OF ECOLOGY, Issue 4 2009Robert M. Chira Abstract The African elephant (Loxodonta africana) is known to greatly affect the structure and dynamics of vegetation. In Mwea National Reserve, elephants foraged mainly on Acacia ataxacantha and Grewia bicolor out of the five most preferred woody species. However, out of the five preferred woody species, only Grewia virosa and G. bicolor showed a positive association between their fresh use and past elephant use. All the five selected woody species showed high coppicing response after foraging, with the highest coppice growth rates recorded for Acacia brevispica and lowest for Grewia tembensis. The mean heights of woody species utilized by elephants were highest for A. brevispica and lowest for G. bicolor. The mean heights of coppices emerging after utilization by elephants were not significantly different for A. ataxacantha but were significantly shorter in the rest of the foraged species. Elephants avoided the coppices of many other woody species notably C. africana, A. tortilis, A. mellifera, Combretum aculeatum among others in the reserve. The objective of this study was to understand the capacity of woody species to recover after utilization by elephants and feeding response of elephants to new woody species re-growth; a cycle that would define the dynamics of food resources and elephant population within the reserve. Résumé On sait que l'éléphant africain Loxodonta africana affecte beaucoup la structure et la dynamique de la végétation. Dans la Réserve Nationale de Mwea, les éléphants consommaient principalement de l'Acacia ataxacantha et du Grewia bicolor parmi les cinq espèces ligneuses préférées. Cependant, parmi ces cinq espèces, seuls Grewia virosa et .G. bicolor présentaient une association positive entre leur utilisation récente et ancienne par les éléphants. Les cinq espèces ligneuses sélectionnées manifestaient une forte repousse en réponse à la consommation des éléphants, et le taux de repousse était le plus élevé a été enregistré chez Acacia brevispica et le plus faible chez Grewia tembensis. La hauteur moyenne des espèces ligneuses consommées par les éléphants était plus grande chez A. brevispica et plus petite chez G. bicolor. La hauteur moyenne des tiges qui avaient repoussé après consommation des éléphants n'était pas significativement différente chez A. ataxacantha, mais elle était significativement plus courte pour les autres espèces consommées. Les éléphants évitaient les taillis de nombreuses autres espèces ligneuses telles que, particulièrement, C. africana, A. tortilis, A. mellifera, Combretum aculeatum, entre autres, dans la réserve. L'objectif de cette étude était de comprendre la capacité des espèces ligneuses de se régénérer après le passage des éléphants, et la réponse alimentaire des éléphants à la nouvelle repousse de différentes espèces ligneuses et d'esquisser ainsi un cycle qui définirait la dynamique des ressources alimentaires et de la population des éléphants de la réserve. [source] The relationships between stocking density and welfare in farmed rainbow troutJOURNAL OF FISH BIOLOGY, Issue 3 2002T. Ellis There is increasing public, governmental and commercial interest in the welfare of intensively farmed fish and stocking density has been highlighted as an area of particular concern. Here we draw scientific attention and debate to this emerging research field by reviewing the evidence for effects of density on rainbow trout. Although no explicit reference to ,welfare' has been made, there are 43 studies which have examined the effects of density on production and physiological parameters of rainbow trout. Increasing stocking density does not appear to cause prolonged crowding stress in rainbow trout. However, commonly reported effects of increasing density are reductions in food conversion efficiency, nutritional condition and growth, and an increase in fin erosion. Such changes are indicative of a reduced welfare status,although the magnitude of the effects has tended to be dependent upon study-specific conditions. Systematic observations on large scale commercial farms are therefore required, rather than extrapolation of these mainly small-scale experimental findings. There is dispute as to the cause of the observed effects of increasing density, with water quality deterioration and/or an increase in aggressive behaviour being variously proposed. Both causes can theoretically generate the observed effects of increasing density, and the relative contribution of the two causes may depend upon the specific conditions. However, documentation of the relationship between density and the effects of aggressive behaviour at relevant commercial densities is lacking. Consequently only inferential evidence exists that aggressive behaviour generates the observed effects of increasing density, whereas there is direct experimental evidence that water quality degradation is responsible. Nevertheless, there are contradictory recommendations in the literature for key water quality parameters to ensure adequate welfare status. The potential for welfare to be detrimentally affected by non-aggressive behavioural interactions (abrasion, collision, obstruction) and low densities (due to excessive aggressive behaviour and a poor feeding response) have been largely overlooked. Legislation directly limiting stocking density is likely to be unworkable, and a more practical option might be to prescribe acceptable levels of water quality, health, nutritional condition and behavioural indicators. [source] Immunolesion of Hindbrain Catecholaminergic Projections to the Medial Hypothalamus Attenuates Penile Reflexive Erections and Alters Hypothalamic Peptide mRNAJOURNAL OF NEUROENDOCRINOLOGY, Issue 5 2002G. S. Fraley Abstract The central mechanisms underlying diabetes-associated impotence are currently unknown. This study utilized immunolesion techniques to eliminate hindbrain catecholaminergic projections to the medial hypothalamus which have been reported to be glucoresponsive. The immunolesioned male rats had an attenuated feeding response to glucoprivic challenge. Furthermore, these lesioned rats had significantly attenuated penile reflexes. Northern blot analyses of hypothalamic oxytocin mRNA expression showed a significant increase; however, neuropeptide Y mRNA expression did not. These results suggest that hindbrain catecholaminergic neurones may alter the expression of hypothalamic neuropeptides that stimulate penile erections based upon glucoregulatory signals from the periphery. [source] Feeding history effects on feeding responses of Rhagoletis indifferens (Dipt., Tephritidae) to GF-120 and NulureJOURNAL OF APPLIED ENTOMOLOGY, Issue 9-10 2006W. L. Yee Abstract:, Effects of feeding history on feeding responses of western cherry fruit fly, Rhagoletis indifferens Curran, to the commercial protein baits GF-120 and Nulure were determined in the laboratory. Flies were kept on 5% sucrose alone or yeast extract and sucrose (Y + S) for 3,7 or 14,16 days and exposed to 24-h-old GF-120 or Nulure drops on artificial leaves. Numbers and durations of feeding events on leaves and durations of non-feeding events were recorded over 1-h periods. Experiments were also conducted to determine effects of Y + S feeding sequences on responses to Nulure, of starvation after sucrose or Y + S feeding on responses to Nulure, and of feeding history on mortality after exposure to GF-120 and Nulure. Protein-deprived flies consistently fed more times on GF-120 and Nulure than protein-fed flies and fed longer. One day of exposure to Y + S or 16 h of starvation after exposure to sucrose caused greater feeding on Nulure than 7 days of exposure to Y + S or 16 h of starvation after exposure to Y + S. Durations of non-feeding events on leaves with sucrose or bait were similar in protein-deprived and -fed flies. Responses of 4- to 6-day-old flies kept on sucrose to 0- and 24-h-old GF-120 or Nulure were similar. More flies kept on sucrose were paralysed or dead at 6,32 h after exposure to GF-120 or Nulure with spinosad than flies kept on Y + S. Results show that complete or long periods of protein deprivation and starvation after sucrose feeding increased feeding responses to GF-120 and Nulure. The general lack of differences in durations of non-feeding events on leaves with sucrose or GF-120 or Nulure in protein-deprived and -fed flies suggests that most protein-deprived flies found baits through chance encounters following normal movement. [source] Vulnerability of an Australian anuran tadpole assemblage to the toxic eggs of the invasive cane toad (Bufo marinus)AUSTRAL ECOLOGY, Issue 2 2010MICHAEL R. CROSSLAND Abstract The invasion of cane toads (Bufo marinus) across tropical Australia has fatally poisoned many native predators; the most frequent victims may be tadpoles of native frogs, which die when they consume the toxic eggs of the toads. Field studies have documented high and species-specific mortality of tadpoles following toad spawning. To clarify the determinants of tadpole vulnerability, we conducted 1593 laboratory trials in which single tadpoles were exposed to 10 toad eggs, either with or without an alternative food source (lettuce). At least some tadpoles within all 15 species tested consumed toad eggs. Interspecific variance in survival rates (from 0 to >70%) was driven by feeding responses not by physiological tolerance to toxins: almost all native tadpoles that consumed eggs died rapidly. Tadpole mortality was decreased by the presence of an alternative food source in four species, increased in two species, and not affected in seven species. In three of four taxa where we tested both small (early-stage) and large (late-stage) tadpoles, both mean survival rates and the effects of alternative food on survival shifted with tadpole body size. Trials with one species (Limnodynastes convexiusculus) showed no significant inter-clutch variation in feeding responses or tolerance to toxins. Overall, our data show that cane toad eggs are highly toxic to native anuran tadpoles, but that whether or not a tadpole is killed by encountering toad eggs depends upon a complex interaction between the native anuran's species, its body size, and whether or not alternative food was present. In nature, larval vulnerability also depends upon the seasonal timing and location of spawning events, and habitat selection and foraging patterns of the tadpoles. Our results highlight the complexity of vulnerability determinants, and identify ecological factors (rather than physiology or feeding behaviour) as the primary determinants of cane toad impact on native tadpoles. [source] | |||||||||||||