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Feeding Activity (feeding + activity)

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Life Sciences	75%
Earth and Environmental Science	19%
Chemistry	5%

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Ecology & Organismal Biology	50%
Entomology	14%
7 Other Subdomains	36%

Selected Abstracts

Sex Differences in Feeding Activity Results in Sexual Segregation of Feral Goats

ETHOLOGY, Issue 5 2008
Robin I. M. Dunbar
Sexual segregation is common in ungulates. We show, in a high latitude population of feral goats where behavioural synchrony and fission rates have been shown to be the best explanation for segregation, that it is differences explicitly in the feeding time requirements of the two sexes (but not those for other activities) that best explains the variations in monthly frequencies of segregation. However, this effect is less marked during winter months when short day length forces the time budgets of the two sexes to converge. We argue that the various explanations for segregation can best be interpreted as separate factors in a multivariate model in which species- and habitat-specific weightings influence the relative importance of these variables, and thus the likelihood that segregation will occur. [source]

Effects of mute swan grazing on a keystone macrophyte

FRESHWATER BIOLOGY, Issue 12 2007
MATTHEW T. O'HARE
Summary 1. This study describes the early summer foraging behaviour of mute swans (Cygnus olor) on the River Frome, a highly productive chalk stream in southern England in which Ranunculus penicillatus pseudofluitans is the dominant macrophyte. 2. A daily maximum of 41 ± 2.5 swans were present along the 1.1 km study reach during the study period (late May to the end of June). The river was the primary feeding habitat. Feeding activity on the river at dawn and dusk was much lower than during daylight, but we cannot rule out the possibility that swans fed during the hours of darkness. 3. The effects of herbivory on R. pseudofluitans biomass and morphology were quantified. Biomass was lower in grazed areas and swans grazed selectively on leaves in preference to stems. A lower proportion of stems from grazed areas possessed intact stem apices and flowering of the plant was reduced in grazed areas. 4. A model, based on the swans' daily consumption, was used to predict the grazing pressure of swans on R. pseudofluitans. The model accurately predicted the number of bird days supported by the study site, only if grazing was assumed to severely reduce R. pseudofluitans growth. The proportion of the initial R. pseudofluitans biomass consumed by a fixed number of swans was predicted to be greater when the habitat area was smaller, initial R. pseudofluitans biomass was lower and R. pseudofluitans was of lower food value. 5. We concluded that the flux of N and P through the study reach was largely unaffected by swan activity. The quality of R. pseudofluitans mesohabitat (the plant as habitat for invertebrates and fish) was significantly reduced by grazing which also indirectly contributed to reduced roughness (Manning's n) and by inference water depth. Wetted habitat area for fish and invertebrates would also be lowered over the summer period as a consequence of the reduction in water depth. It was estimated that, while grazing, an individual swan may eat the same mass of invertebrates per day as a 300-g trout. 6. There is a need to manage the conflict between mute swans and the keystone macrophyte, R. pseudofluitans, in chalk streams, and the modelling approach used here offers a potentially useful tool for this purpose. [source]

The effect of food on microparasite transmission in the waterflea Daphnia magna

OIKOS, Issue 2 2005
Daniel Fels
Studies on dynamics of trophic transmission usually refer to the predation of animals that contain parasites. Here, in contrast, I study the transmission of external stages of parasites namely of spores of the microsporidian gut parasites Glugoides intestinalis and Micro1. These spores are filter fed by the waterflea Daphnia magna and I was particularly interested in the effect of food on transmission success. It was hypothesized that food has a double impact on transmission success because of increased spore uptake on the one hand and increased spore defecation of infected waterfleas on the other. I tested for these assumed food effects in exposure experiments where transmission could occur naturally from infected to uninfected waterfleas in the presence or absence of food. The major assumptions were confirmed. In one system transmission success was increased fourfold in the presence of food and feeding infected hosts had lower spore loads. The other system showed evidence for these effects. Feeding activity correlated positively with food in both systems and spore loads in infected waterfleas partially determined spore loads in exposed waterfleas. I discuss the impact of food on infected and uninfected waterfleas in particular and on transmission success and epidemiology in general. [source]

Water temperature determines strength of top-down control in a stream food web

FRESHWATER BIOLOGY, Issue 8 2005
DAISUKE KISHI
Summary 1. We examined effects of water temperature on the community structure of a three trophic level food chain (predatory fish, herbivorous caddisfly larvae and periphyton) in boreal streams. We used laboratory experiments to examine (i) the effects of water temperature on feeding activities of fish and caddisfly larvae and on periphyton productivity, to evaluate the thermal effects on each trophic level (species-level experiment), and (ii) the effects of water temperature on predation pressure of fish on abundance of the lower trophic levels, to evaluate how temperature affects top-down control by fish (community-level experiment). 2. In the species-level experiment, feeding activity of fish was high at 12 °C, which coincides with the mean summer temperature in forested streams of Hokkaido, Japan, but was depressed at 3 °C, which coincides with the mean winter temperature, and also above 18 °C, which coincides with the near maximum summer temperatures. Periphyton productivity increased over the range of water temperatures. 3. In the community-level experiments, a top-down effect of fish on the abundance of caddisfly larvae and periphyton was clear at 12 °C. This effect was not observed at 3 and 21 °C because of low predation pressure of fish at these temperatures. 4. These experiments revealed that trophic cascading effects may vary with temperature even in the presence of abundant predators. Physiological depression of predators because of thermal stress can alter top-down control and lead to changes in community structure. 5. We suggest that thermal habitat alteration can change food web structure via combinations of direct and indirect trophic interactions. [source]

Sex-dependent use of information on conspecific feeding activities in an amphibian urodelian

FUNCTIONAL ECOLOGY, Issue 2 2009
Pedro Aragón
Summary 1Animals can make decisions by observing the behaviour of others. Their decisions vary depending on whether the benefits of using such information exceed the costs. Thus, it is worthwhile to explore the potential costs associated with different sources of information to understand the consequences of sociality. Previous studies focused mainly on the costs inherent to information gathering, whereas sex differences with regard to the costs arising from information use have received less attention. 2To explore this further I performed two complementary experiments. The first experiment aimed to examine individual responses to different combinations of information types that are likely to appear in nature, to test whether there is a sex-dependent response in the Bosca's newt, Lissotriton boscai. I tested the time needed for individuals to eat food items by trial-and-error tactics (personal information), and when a conspecific, which was eating or not, was added to the food cue. The second experiment aimed to evoke social interactions that are likely to arise after the choice of using information on conspecific feeding activities is made. I examined the potential costs associated with direct competition between same-sex pairs in food-limited conditions. 3Results of experiment 1 revealed that in both sexes the latency to eat food items was shorter in the presence of non-feeding conspecifics, but only females took advantage when information related to feeding activities where added to the food cue. Results of experiment 2 showed that when faced with a limited resource of food, females were more prone to engage in costly interactions. 4This study suggests that the balance between costs and benefits associated with the short-term use of information on conspecific feeding behaviour in combination with food cues may differ between sexes. Differential information uses by sexes might have profound consequences in intraspecific relationships and in the evolution of vertebrates' social systems. [source]

Unusual synchronization of Red Sea fish energy expenditures

ECOLOGY LETTERS, Issue 2 2003
Lewi Stone
Abstract The highly gregarious goat fish Parupeneus forskalii found in the Red Sea at Eilat, Israel exhibit highly synchronous swimming and feeding activity. Five fish were studied under controlled conditions and highly resolved time-series of their energy expenditures were measured. All fish demonstrated strong phase synchronization in that their activity levels, although erratic in time and intensity, were collectively coordinated and peaked simultaneously together. The synchronization of these wildly varying, and possibly chaotic signals of energy expenditures, were quantified using phase analysis. We suggest that, ecologically, this collective synchronization is a strategy that increases food-catch. [source]

Feeding ecology of fishes associated with Egeria spp. patches in a tropical reservoir, Brazil

ECOLOGY OF FRESHWATER FISH, Issue 1 2006
F. M. Pelicice
Abstract ,, This research characterised feeding ecology of fishes associated with patches of Egeria najas and Egeria densa, two submerged macrophytes, in Rosana Reservoir, Upper Paraná River basin, Brazil. Fishes were sampled using a 1 m2 throw trap in patches of different macrophyte biomass and in three diel periods during a wet season. Fish diet (10 species) was primarily composed of autochthonous items (zooplankton, algae and aquatic insect larvae). Almost all intra-specific diet patterns had moderate to low levels of diet similarity, indicating a high variability in diet. Some species showed no diel patterns in feeding activity, whereas others were primarily diurnal or nocturnal. No differences in feeding activity were observed among habitats of medium and high macrophyte biomasses, and species tended to feed on the same items among these habitats. The most abundant fish species demonstrated low inter-specific diet overlap and appear not to compete for food resources. We suggest that Egeria patches are feeding grounds and shelter for small-sized fish species. Resumen 1. Esta investigación caracterizó la ecología trófica de las especies de peces asociadas a manchas de Egeria najas e E. densa, dos macrofitas sub-aquaticas, en la represa de Rosana (alto Río Paraná, Brasil). Los peces fueron colectados con un throw trap de 1 m2 en manchas con distintas biomasas de macrófitas y en tres períodos del día, durante la estación lluviosa. 2. La dieta de 10 especies estuvo compuesta principalmente de componentes autóctonos (zooplancton, algas y larva de insectos acuáticos). Casi todas las especies presentaron patrones de dieta intra-específica con similitudes moderadas o bajas (elevada variabilidad). Algunas especies no mostraron ningún patrón de actividad alimenticia durante el día mientras que otras fueron principalmente diurnas o nocturnas. No se observó ninguna diferencia de actividad alimenticia entre los habitats de media y alta biomasa de macrófitas, y las especies tendieron a alimentarse de los mismos componentes entre estos habitats. 3. Las especies de peces más abundantes mostraron un solapamiento alimenticio bajo y parecen no competir por recursos alimenticios. Sugerimos que las manchas de Egeria funcionan como lugar de alimentación y abrigo para los peces de pequeño tamaño. [source]

Community heterogeneity and single-cell digestive activity of estuarine heterotrophic nanoflagellates assessed using lysotracker and flow cytometry

ENVIRONMENTAL MICROBIOLOGY, Issue 7 2010
Eva Sintes
Summary Heterotrophic nanoflagellates (HNFs) are an essential component of all aquatic microbial food webs, and yet the exploration of the numerical and single-cell responses of these organisms in mixed assemblages still represents a major technical challenge. LysoTracker Green staining combined with flow cytometry was recently proposed for the enumeration of aquatic HNFs. Here we show that LysoTracker Green not only allows the enumeration of HNFs in estuarine samples with a wide range of HNF abundances, but also allows the discrimination of distinct HNF populations in mixed assemblages. In addition, the resulting cytometric parameters can be used to characterize cell size and the level of activity of the cells in the different populations that are detected. LysoTracker Green accumulates preferentially in lysosomes, and we demonstrate that the green fluorescence emission from HNF cells stained with LysoTracker strongly correlates with cell-specific ,-glucosaminidase (,-Gam) activity, a key digestive enzyme of lysosomal origin in eukaryotic cells. Our results further show that different populations that develop in estuarine regrowth cultures are characterized by different intrinsic ranges of size and of feeding activity, and that there is a wide range of single-cell responses within these HNF populations. We found a large degree of uncoupling between cell size and feeding activity, both between and within HNF populations, and there appears to be no clear allometric scaling of feeding activity. We were able to reconstruct the succession of distinct HNF populations that developed during the regrowth experiments, and explore the complex interactions that occurred between numerical (change in abundance of the cytometric populations) and single-cell HNF responses. [source]

Interactions between fauna and sediment control the breakdown of plant matter in river sediments

FRESHWATER BIOLOGY, Issue 4 2010
SIMON NAVEL
Summary 1. A substantial portion of particulate organic matter (POM) is stored in the sediment of rivers and streams. Leaf litter breakdown as an ecosystem process mediated by microorganisms and invertebrates is well documented in surface waters. In contrast, this process and especially the implication for invertebrates in subsurface environments remain poorly studied. 2. In the hyporheic zone, sediment grain size distribution exerts a strong influence on hydrodynamics and habitability for invertebrates. We expected that the influence of shredders on organic matter breakdown in river sediments would be influenced strongly by the physical structure of the interstitial habitat. 3. To test this hypothesis, the influence of gammarids (shredders commonly encountered in the hyporheos) on degradation of buried leaf litter was measured in experimental systems (slow filtration columns). We manipulated the structure of the sedimentary habitat by addition of sand to a gravel-based sediment column to reproduce three conditions of accessible pore volume. Ten gammarids were introduced in columns together with litter bags containing alder leaves at a depth of 8 cm in sediment. Leaves were collected after 28 days to determine leaf mass loss and associated microbial activity (fungal biomass, bacterial abundance and glucosidase, xylosidase and aminopeptidase activities). 4. As predicted, the consumption of buried leaf litter by shredders was strongly influenced by the sediment structure. Effective porosity of 35% and 25% allowed the access to buried leaf litter for gammarids, whereas a lower porosity (12%) did not. As a consequence, leaf litter breakdown rates in columns with 35% and 25% effective porosity were twice as high as in the 12% condition. Microbial activity was poorly stimulated by gammarids, suggesting a low microbial contribution to leaf mass loss and a direct effect of gammarids through feeding activity. 5. Our results show that breakdown of POM in subsurface waters depends on the accessibility of food patches to shredders. [source]

Species-specific responses of planktivorous fish to the introduction of a new piscivore: implications for prey fitness

FRESHWATER BIOLOGY, Issue 9 2007
FRANZ HÖLKER
Summary 1. Antipredator behaviour by the facultative planktivorous fish species roach (Rutilus rutilus), perch (Perca fluviatilis) and rudd (Scardinius erythrophthalmus) was studied in a multi-year whole-lake experiment to evaluate species-specific behavioural and numerical responses to the stocking of pikeperch (Sander lucioperca), a predator with different foraging behaviour than the resident predators large perch (P. fluviatilis) and pike (Esox lucius). 2. Behavioural responses to pikeperch varied greatly during the night, ranging from reduced activity (roach and small perch) and a shift in habitat (roach), to no change in the habitat use and activity of rudd. The differing responses of the different planktivorous prey species highlight the potential variation in behavioural response to predation risk from species of similar vulnerability. 3. These differences had profound effects on fitness; the density of species that exhibited an antipredator response declined only slightly (roach) or even increased (small perch), whereas the density of the species that did not exhibit an antipredator response (rudd) decreased dramatically (by more than 80%). 4. The maladaptive behaviour of rudd can be explained by a ,behavioural syndrome', i.e. the interdependence of behaviours expressed in different contexts (feeding activity, antipredator) across different situations (different densities of predators). 5. Our study extends previous studies, that have typically been limited to more controlled situations, by illustrating the variability in intensity of phenotypic responses to predators, and the consequences for population density, in a large whole-lake setting. [source]

Water temperature determines strength of top-down control in a stream food web

Day-Night Vertical Distribution and Feeding Patterns of Fourth Instar ofChaoborus Larvae in a Neotropical Reservoir (Socuy Reservoir, Venezuela)

INTERNATIONAL REVIEW OF HYDROBIOLOGY, Issue 2 2005
Carlos López
Abstract The day-night vertical distribution, diel feeding activity and diet of fourth instar of Chaoborus larvae were analyzed in lacustrine zone of a neotropical reservoir which shows seasonally contrasting hypolimnetic oxygen conditions. Larvae stayed in sediment and water bottom during day and ascended to surface during night. Results indicate that feeding activity is limited mainly to the plankton population. Phytoplankton, rotifers or remains of Chaoborus larvae were not found in crops. With the exception of ostracods, all crustacean prey available in the zooplankton occurred in the guts. Ceriodaphnia cornuta and Moina micrura were the most frequent food items (about 75% of occurrence frequency) and were positively selected. The remainder crustacean zooplankton taxa were negatively selected by larvae. The most intense feeding activity in larvae occurred near midnight and sunrise, in dates when the hypolimnion was anoxic. When oxygen was available on the bottom, a higher and not changing diel feeding activity was detected. Our results indicate that vertical migration may promote a spatial separation between larvae and zooplankton, and feeding activity of larvae occurred only when both overlapped. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Biology and control of Dicladispa gestroi Chapuis (Col., Chrysomelidae)

JOURNAL OF APPLIED ENTOMOLOGY, Issue 9-10 2001
V. Delucchi
The beetle Dicladispa gestroi is known only from Madagascar, where it is considered to be a pest of rice. Research were carried out from 1885 to 1994 in the Alaotra lake region, the main rice-producing area of the country, characterized by a warm rainy season from October to April and a cool dry season from April to October. The adult beetles invade the rice nurseries and the first direct-seeded fields at the beginning of the rainy season; they have a gregarious behaviour and their feeding activity, together with the mines bored by the larvae, determines a change of colour from green to pale yellow in the damage areas, which resemble outbreak areas of rice leafhoppers. Oviposition takes place only on young rice plants in the tillering stage. Females emerging after the end of February enter a reproductive diapause and leave the rice fields to ,hibernate'. Temperature summations for the egg, larval, and pupal development, as well as for the preoviposition period have been calculated. There is no yield loss up to a larval density of 0.6 per leaf and this economic injury level is seldom exceeded in the Alaotra lake region. Life tables carried out under field conditions show that chalcid parasitoids are the main mortality factor and are responsible for the collapse of entire outbreak areas. Since the discovery of the rice yellow mottle virus in 1989 in the Alaotra lake region and the disease transmission by chrysomelids, the pest status of D. gestroi has changed and control measures have to be applied. However, to avoid interference with the action of the parasitoids, chemical applications should be limited to rice nurseries. [source]

The diet of blue whiting, hake, horse mackerel and mackerel off Portugal

JOURNAL OF APPLIED ICHTHYOLOGY, Issue 1 2002
H. N. Cabral
This paper deals with the diets of blue whiting Micromesistius poutassou (Risso 1810), hake Merluccius merluccius (L. 1758), horse mackerel Trachurus trachurus (L. 1758), and mackerel Scomber scombrus (L. 1758) off Portugal and explores variations in fish length, water depth, latitude and season. All four species feed on fish; however, hake and mackerel are the first and second most important predators, respectively, blue whiting being the most important fish prey for both species. The diets of blue whiting and horse mackerel are composed mainly of crustaceans. Diet variations according to predator fish size are more important than either latitude or depth. In the diets of blue whiting, hake and horse mackerel, prey importance increases with predator size. For blue whiting and horse mackerel, diet variations with fish length and water depth are correlated: small fish are closely associated with coastal areas where they feed on copepods and decapod larvae. Seasonality in the diet is apparent for blue whiting, hake and mackerel. For blue whiting, the decapod Pasiphaea sivado is the most important prey in summer and autumn, being replaced by the euphausid Meganyctiphanes norvegica in winter. In the diet of hake, seasonality was characterised by the major importance of Macroramphosus scolopax in autumn, whereas the diet of mackerel consisted of zooplankton in summer, fish and decapods in autumn and decapod larvae in winter. Seasonal changes in the diet of horse mackerel correspond to a higher diversity of prey in autumn compared to other seasons (although euphausids are the main prey in all seasons). Seasonality in feeding activity is not as marked for the other species as it is for horse mackerel; the percentage of empty stomachs of horse mackerel is greatest in winter, when spawning takes place at the Portuguese coast. [source]

Do Meyer's Parrots Poicephalus meyeri benefit pollination and seed dispersal of plants in the Okavango Delta, Botswana?

AFRICAN JOURNAL OF ECOLOGY, Issue 3 2010
Rutledge S. Boyes
Abstract Recent studies of new world parrots repeatedly document, with few exceptions, that parrots are wasteful and destructive predispersal seed predators that are unlikely to contribute towards pollination and seed dispersal. Few detailed studies, however, have assessed the contribution of African parrots to forest ecology by quantifying the potential net benefit of seed and flower predation by parrots for most tree species in their diet. Due to the incidence of pollen on the heads of Meyer's Parrots when feeding on Leguminosae flowers and the dispersal of viable seeds to the ground during seed predation, we compared destruction rates, when feeding on pods, fruits and flowers, with dispersal rates of viable seeds to the ground and frequency of head contact with reproductive apparatus to estimate net benefit from Meyer's Parrot feeding activity. Meyer's Parrots were not implicated in endo- or epizoochory, but they dropped uneaten fruit pulp and seeds to the ground during feeding bouts, thus providing ripe, undamaged seeds to secondary seed dispersers. This link with forest recruitment was weak, as all tree species utilized by Meyer's Parrots either had more significant primary dispersal agents or were primarily wind-dispersed. In most cases, the negative effect of seed predation outweighed any positive effects in terms of dispersal, whereby almost three times more seeds were consumed or destroyed than were dispersed to the ground. Significantly, only Sclerocarya birrea caffra recorded marginal net dispersal benefit from utilization by Meyer's Parrots. Due to low relative resource abundance and high destruction rate, feeding activity on Berchemia discolor may be significant enough to influence its spatial distribution and abundance. Utilization of flowers of Kigelia africana and Adansonia digitata by parrots likely had a significant negative impact on pollination. Feeding on Acacia nigrescens flowers, however, was potentially advantageous to their pollination. We conclude that Poicephalus parrots are net consumers of ripe, undamaged seeds and flowers, thus having an overall negative impact on forest recruitment in subtropical Africa. Résumé Les études récentes des perroquets du nouveau monde disent toujours, à quelques exceptions près, que les perroquets sont des prédateurs qui gaspillent et détruisent les semences avant leur dispersion et qu'ils sont donc peu susceptibles de contribuer à la fertilisation et à la dispersion des graines. Cependant, peu d'études détaillées ont évalué la contribution des perroquets africains à l'écologie des forêts en quantifiant le bénéfice net potentiel de la consommation des graines et des fleurs pour la plupart des espèces d'arbres qui entrent dans leur régime alimentaire. Sachant que la tête des perroquets de Meyer se charge de pollen lorsqu'ils se nourrissent de fleurs de légumineuses et qu'ils dispersent des semences viables sur le sol lorsqu'ils en consomment, nous comparons le taux de destruction, lorsqu'ils mangent des gousses, des fruits et des fleurs, avec le taux de dispersion de semences viables sur le sol et la fréquence des contacts de leur tête avec l'appareil reproducteur des plantes, pour estimer le bénéfice net de l'alimentation du perroquet de Meyer. Ces perroquets n'étaient pas impliqués dans l'endo- ou l'épizoochorie, mais lorsqu'ils mangeaient, ils laissaient tomber de la pulpe et des graines de fruits non consommées, fournissant ainsi des semences intactes à des disperseurs secondaires. Ce rapport avec le recrutement des forêts était faible dans la mesure où toutes les semences des espèces d'arbres fréquentées par les perroquets de Meyer soit avaient des agents de dispersion primaires plus importants, soit étaient principalement dispersées par le vent. Dans la plupart des cas, l'effet négatif de la consommation des semences dépassait tout effet positif en termes de dispersion, et presque trois fois plus de graines étaient mangées ou détruites que dispersées sur le sol. Il est intéressant de noter que seul Sclerocarya birrea caffra présentait un bénéfice net de dispersion marginal dûà la fréquentation des perroquets de Meyer. En raison de la faible abondance relative de ressources et du taux de destruction élevé, la consommation de Berchemia discolor pourrait être assez significative pour influencer sa distribution spatiale et son abondance. La consommation des fleurs de Kigelia africana et d'Adansonia digitata par les perroquets avait probablement un impact négatif sur leur pollinisation. Mais la consommation des fleurs d'Acacia nigrescensétait peut-être avantageuse pour la pollinisation. Nous concluons que les perroquets Poicephalus sont des consommateurs nets de graines et de fleurs mûres et intactes, et qu'ils ont donc un impact global négatif sur le recrutement des forêts en Afrique subtropicale. [source]

Feeding ecology and growth of neonate and juvenile blacktip sharks Carcharhinus limbatus in the Timbalier,Terrebone Bay complex, LA, U.S.A.

JOURNAL OF FISH BIOLOGY, Issue 3 2008
K. P. Barry
Stomach contents and vertebrae from neonate and juvenile blacktip sharks Carcharhinus limbatus (n= 334) were examined to describe their diet, feeding patterns and growth within the Timbalier,Terrebone Bay complex, LA, U.S.A. In the study area, both neonate and juvenile C. limbatus feed primarily on gulf menhaden Brevoortia patronus. However, based on the index of relative importance (IRI), gulf menhaden constituted a larger portion of the diet of neonates (84·05 %IRI) than for juveniles (47·91 %IRI). An increase in the index of relative fullness between the afternoon and dusk time intervals and a large decrease in the percentage of empty stomachs between the night and early morning time intervals suggested that these fish exhibited a diel feeding pattern with crepuscular periods being the times of highest feeding activity. A higher percentage of empty stomachs (neonates 68% and juveniles 39%) and a significantly lower growth rate (age 0+ year C. limbatus, 0·62 mm day,1; age 1+ year fish, 0·89 mm day,1) could indicate that neonate C. limbatus are less efficient predators than older conspecifics. [source]

Status, habitat use, and vulnerability of the European ggrayling in Austrian waters

JOURNAL OF FISH BIOLOGY, Issue 2001
F. Uiblein
The European grayling Thymallus thymallus is widely distributed in Austria, occurring in all eight rural provinces. However, in recent years, an increasing number of studies report severe declines in population sizes. Since 1997, the grayling has had the status of an endangered species in Austria. In 1997 the multidisciplinary research programme ,Local Adaptation, Threat, and Conservation of European Grayling' has carried out three projects in Upper Austria, Salzburg, and Carinthia. Research has included repeated electro-fishing in selected stretches of eight rivers and the collection of data on habitat characteristics, fish species composition, population abundance and size distribution, growth and body condition, as well reproductive timing, and migratory activities of grayling. Furthermore, genetic and morphological variation among grayling populations has been studied as well as the number, habitat use and feeding activity of cormorants. Evidence is provided for the existence of distinct negative effects caused by single factors or combinations of factors on grayling stocks in each of the river stretches studied. [source]

Treatment development for systemic Tetrahymena sp. infection in guppies, Poecilia reticulata Peters

JOURNAL OF FISH DISEASES, Issue 6 2010
M Pimenta Leibowitz
Abstract Antibacterial and antiparasitic agents and a cysteine protease inhibitor (E-64) were tested against Tetrahymena infection, a serious problem in guppy production worldwide. Chemicals were tested in vitro by a colorimetric assay for Tetrahymena survival. The most effective were niclosamide, albendazole and chloroquine, with 23%, 35% and 60% survival, respectively, following 2-h exposure to 100 ppm. Longer incubation periods resulted in greater reductions in survival. Niclosamide was further studied in vivo at different dosages, administered orally to Tetrahymena -infected guppies. Mortality rates were significantly lower in all treatment groups; in trial I, 30% and 33% mortality in 5 and 40 mg kg,1 niclosamide-fed fish vs. 59% mortality in controls; in trial II, 35%, 13% and 10% in 50, 100 and 200 mg kg,1 niclosamide-fed fish vs. 64% in controls. The effect of the cysteine protease inhibitor E64 was tested in tissue culture, by measuring histolytic activity of the parasite (Tet-NI) on a guppy-fin cell line, based on cell depletion. Tet-NI feeding activity was significantly reduced following pretreatment with E-64 relative to non-treated Tet-NI. E-64-pretreated Tet-NI was injected i.p. into guppies: recorded mortality rates were significantly lower (35%) than that in non-treated Tet-NI (60%), suggesting inhibition of the parasite's cysteine protease as a possible therapeutic approach. [source]

Survival at low temperature of larvae of the pine processionary moth Thaumetopoea pityocampa from an area of range expansion

AGRICULTURAL AND FOREST ENTOMOLOGY, Issue 3 2009
Gernot Hoch
Abstract 1,Larvae of Thaumetopoea pityocampa (Lepidoptera: Notodontidae) develop throughout the winter, although their feeding activity and survival can be impaired by adverse climatic factors. The present study investigated the survival at low temperature of larvae originating from a population with range expansion in an alpine valley in Northern Italy. 2,The supercooling point of individually analysed larvae averaged at ,7 °C. This value insufficiently described the cold hardiness of the larvae; 39% of the tested larvae were alive when returned to room temperature immediately after freezing. When larval colonies inside their nest were exposed to ,17 °C for 1 h after gradual temperature decrease, survival was 70.4%. 3,Rearing of larvae in the laboratory at different day/night temperatures indicated an effect of cumulative chill injury on larvae. A logistic regression explained the relationship between negative thermal sum (h°C below 0 °C) received in the laboratory experiment and larval survival. A similar relationship was demonstrated between negative thermal sum and survival of larval colonies in the field. 4,In the laboratory experiment, some tested larvae were able to survive for up to 8 weeks without feeding depending on rearing temperature. As expected, feeding occurred only when larvae were reared at temperatures of 9 °C day/0 °C night. 5,We classify the larvae of T. pityocampa as being moderate freezing tolerant. The winter behaviour allows this species to track climate warming by a rapid expansion into those areas that become compatible with the insect's development. [source]

Production and Processing Trait Comparisons of Channel Catfish, Blue Catfish, and Their Hybrids Grown in Earthen Ponds

JOURNAL OF THE WORLD AQUACULTURE SOCIETY, Issue 6 2008
Mingkang Jiang
Fingerling HS-5 channel catfish, Ictalurus punctatus, NWAC 103 channel catfish, D&B blue catfish, Ictalurus furcatus, HS-5 female channel × D&B male blue catfish F1 hybrids, and NWAC 103 female channel × D&B male blue catfish F1 hybrids were stocked into twenty-five 0.04-ha earthen ponds at 12,500 fish/ha and grown for 277 d. Fish were fed daily at rates from 1.0 to 3.0% biomass based on feeding activity and temperature and adjusted weekly assuming a feed conversion ratio (FCR) of 1.8 and 100% survival. At harvest, 40 fish from each pond were sampled, and all other counted and weighed. Mean survival, growth rate indexes (a), FCR, and skin-on fillet percentages were not significantly different. Mean harvest weights and net production were higher for HS-5 channel and its hybrid than for the NWAC 103 channel, NWAC 103 hybrid, and D&B blue catfish, partially because of their larger mean stocking weights. D&B blue catfish was more uniform in size than NWAC 103 channel and NWAC 103 hybrid. D&B blue catfish was the easiest to seine. HS-5 hybrids and NWAC 103 hybrids had lower mean head percentage and a better processing yield than their parent channel catfish. [source]

Replacement of Fish Meal with Poultry By-product Meal as a Protein Source in Pond-raised Sunshine Bass, Morone chrysops , × M. saxatlis ,, Diets

JOURNAL OF THE WORLD AQUACULTURE SOCIETY, Issue 5 2008
Harvey J. Pine
Replacement of fish meal (FM) as a protein source with alternative sources of protein in aquaculture diets has been widely explored in aquaculture. The goal of replacement of FM in production diets is to maintain growth, lower production costs, and increase sustainability. Evaluation of the replacement of FM with poultry by-product meal (PBM) in phase II sunshine bass diets, Morone chrysops × M. saxatilis, was conducted in ponds over 246 d. Four diets were formulated to be isonitrogenous (37%) and isocaloric (4 kcal/g) with different levels of FM replacement with PBM (0, 33, 67, and 100%, Diets 1,4, respectively). Twelve ponds were stocked with 400 phase II sunshine bass (mean weight 5.6 g) and randomly assigned one of the four diets. Fish were fed below satiation based on predicted growth and feed conversion, initially once daily (1700 h) and then twice daily (0700 and 1700 h) as water temperatures and feeding activity increased. Diets were evaluated based on production and performance indicators, body composition, and economic analysis. Production results revealed no significant differences in mean final individual fish weight (511 ± 21 g), net production (4257 ± 247 kg/ha), and survival (85 ± 2%). No significant differences occurred between the performance indicators: mean feed conversion ratio (2.47 ± 0.11), specific growth rate (1.84 ± 0.02), and protein conversion efficiency (23 ± 1.3%). Body composition was statistically similar for mean percent fillet weight (49 ± 0.6%) and percent intraperitoneal fat (9.8 ± 1.0%); however, the hepatosomatic index was significantly different between Diets 3 (3.7 ± 0.1%) and 4 (3.2 ± 0.1%). Mean proximate analysis of whole fish (dry weight basis) was not significantly different among treatments yielding the following: percent protein (46 ± 0.4%), lipid (47 ± 1.3%), and ash (8 ± 0.7%). Mean fillet composition (dry weight basis) also revealed no significant differences: percent protein (72 ± 0.8%), percent lipid (30 ± 1.6%), and percent ash (5 ± 0.2%). Proximate analysis was also performed on the diets and revealed a significantly lower protein content in Diet 3 (34.3 ± 0.5%) compared to the other diets (37.1 ± 0.4%). Amino acid analysis of the diets indicated a possible deficiency in methionine in Diets 3 and 4. Based on production, performance, and body composition, the results indicate that complete replacement of FM with PBM in sunshine bass diets is feasible; however, economic analysis suggests that the replacement of FM with PBM may result in reduced revenue over feed costs. [source]

Activity following arousal in winter in North American vespertilionid bats

MAMMAL REVIEW, Issue 4 2006
JUSTIN G. BOYLES
ABSTRACT 1Many bat species hibernate to conserve energy during winter and like all hibernators they commonly arouse. During these arousals, some bats may undertake activities away from the hibernation site. Systematic ecological studies of the frequency and purpose of winter activity in temperate zone bats of North America are rare and much of the literature involves observations of single individuals or unmarked populations. 2We review the available literature on winter activity among North American vespertilionid bats to highlight the paucity of data on this subject and to stimulate future research. Due to the lack of repeated, systematic studies on most North American species, the conclusions drawn are general or pertain only to parts of the geographical range of any species. 3We suggest that winter activity is ubiquitous among temperate zone bats, but the degree and purpose of activity varies greatly between and within species. In general, cave-dwelling bats tend to be relatively inactive compared with tree and foliage roosting bats during winter. 4Cave-dwelling and tree cavity-dwelling species do not appear to feed, but they do drink and occasionally copulate during the hibernation period. Species that hibernate in foliage or leaf litter are the most active species during winter and may feed and drink throughout winter, although they probably do not copulate because of their solitary nature. 5We encourage researchers to conduct studies on all aspects of winter activity for North American vespertilionids across wide latitudinal and altitudinal gradients. We suggest studies in the near future be focused on estimating the energetic costs and benefits of winter activity through determination of the frequency and intensity of winter feeding activity and more thorough examinations of movements within and among caves. Studies on common, wide-ranging species have the potential to illuminate large-scale patterns and differences and should be favoured over studies on rarer species. [source]

Risk posed to honeybees (Apis mellifera L, Hymenoptera) by an imidacloprid seed dressing of sunflowers

PEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 3 2001
Richard Schmuck
Abstract In a greenhouse metabolism study, sunflowers were seed-treated with radiolabelled imidacloprid in a 700,g,kg,1 WS formulation (Gaucho® WS 70) at 0.7,mg AI per seed, and the nature of the resulting residues in nectar and pollen was determined. Only the parent compound and no metabolites were detected in nectar and pollen of these seed-treated sunflower plants (limit of detection <0.001,mg,kg,1). In standard LD50 laboratory tests, imidacloprid showed high oral toxicity to honeybees (Apis mellifera), with LD50 values between 3.7 and 40.9,ng per bee, corresponding to a lethal food concentration between 0.14 and 1.57,mg,kg,1. The residue level of imidacloprid in nectar and pollen of seed-treated sunflower plants in the field was negligible. Under field-growing conditions no residues were detected (limit of detection: 0.0015,mg,kg,1) in either nectar or pollen. There were also no detectable residues in nectar and pollen of sunflowers planted as a succeeding crop in soils which previously had been cropped with imidacloprid seed-treated plants. Chronic feeding experiments with sunflower honey fortified with 0.002, 0.005, 0.010 and 0.020,mg,kg,1 imidacloprid were conducted to assess potential long-term adverse effects on honeybee colonies. Testing end-points in this 39-day feeding study were mortality, feeding activity, wax/comb production, breeding performance and colony vitality. Even at the highest test concentration, imidacloprid showed no adverse effects on the development of the exposed bee colonies. This no-adverse-effect concentration of 0.020,mg,kg,1 compares with a field residue level of less than 0.0015,mg,kg,1 (,=, limit of detection in the field residue studies) which clearly shows that a sunflower seed dressing with imidacloprid poses no risk to honeybees. This conclusion is confirmed by observations made in more than 10 field studies and several tunnel tests. © 2001 Society of Chemical Industry [source]

Temporal pattern of feeding activity in the firebug Pyrrhocoris apterus and its relation to sex, wing dimorphism and physiological state of adults

PHYSIOLOGICAL ENTOMOLOGY, Issue 1 2007
RADOMÍR SOCHA
Abstract The present study tested whether the pattern of feeding activity in the firebug Pyrrhocoris apterus (L.) is sex- and wing morph-related, diurnal or nocturnal, as well as whether the feeding rhythm persists in constant darkness. Temporal patterns of feeding activity are analysed in macropterous and brachypterous adults reared under long-day (LD 18 : 6 h) and short-day (LD 12 : 12 h) photoperiods, and in adults transferred to constant darkness. In females, the total feeding activity is highest in long-day reproductively active brachypters, intermediate in short-day diapausing brachypters, and lowest in macropters; the differences among males are substantially smaller. Although the total feeding activity of macropterous males is higher than in macropterous females, no sex-related differences are found in feeding activity of diapausing and reproductively active brachypters. The frequency of feeding exhibits sex-related differences, with obviously higher values in males. Mean feeding periods of macropterous and reproductively active brachypterous males are shorter than in females of the same wing morph. Mean interfeeding periods are longest in macropters, intermediate in diapausing brachypters, and shortest in reproductively active brachypters, and always lower in males than in females. The study shows that the feeding activity of P. apterus adults is age-, sex- and wing morph-related, and exhibits a diurnal pattern, except in reproductively active brachypterous females. The latter do not express a clear diurnal rhythm of feeding, presumably because of interactions with cycles of egg development and oviposition. The persistence of diurnal rhythm of feeding activity in short-day brachypterous females transferred to constant darkness indicates an endogeneity of this rhythm in P. apterus. [source]

The feeding ecology and activity budget of proboscis monkeys

AMERICAN JOURNAL OF PRIMATOLOGY, Issue 6 2009
Ikki Matsuda
Abstract A group of proboscis monkeys (Nasalis larvatus) consisting of an alpha-male, six adult females, and several immatures was observed from May 2005,2006. We collected over 1,968,hr of focal data on the adult male and 1,539,hr of focal data on the six females in a forest along the Menanggul River, Sabah, Malaysia. Availability and seasonal changes in plant species consumed by the focal monkeys were determined by vegetation surveys carried out across an area of 2.15,ha along 200,500,m trails in riverine forest. A total of 188 plant species were consumed by the focal monkeys. The activity budget of members of our study group was 76.5% resting, 19.5% feeding, and 3.5% moving. Young leaves (65.9%) and fruits (25.9%) accounted for the majority of feeding time. Over 90% of fruit feeding involved the consumption of unripe fruits and in the majority of case both the fruit flesh and seeds were eaten. Although fruit eating was rare in some months, during other times of the year time fruit feeding exceeded the time devoted to young leaves. We found that monthly fruit availability was positively related to monthly fruit eating and feeding activity, and seasonal fluctuations in dietary diversity were significantly affected by fruit eating. These results suggest that fruit availability and fruit-eating behaviors are key factors that influence the activity budget of proboscis monkeys. Earlier assumptions that colobine monkeys are obligate folivores do not apply well to proboscis monkeys and certain other colobines. Our findings may help contribute to a better understanding of the dietary adaptations and feeding ecology of Asian colobines. Am. J. Primatol. 71:478,492, 2009. © 2009 Wiley-Liss, Inc. [source]

Food uptake in the mixotrophic Dinophysis acuminata

THE JOURNAL OF EUKARYOTIC MICROBIOLOGY, Issue 2 2005
LUCIE MARANDA
Evidence of food uptake in the photosynthetic genus Dinophysis comes solely from the presence of food vacuoles, as no photosynthetic cells have ever been observed in the act of feeding. We examined the feeding ecology of D. acuminata in natural populations and under laboratory conditions. Using depth-integrated sampling of the water column, we determined the frequency of food vacuolated cells at 2-h intervals over a 24-h period in a shallow marine embayment. Food vacuoles in preserved cells were enumerated using Nomarski differential interference contrast microscopy; ultrastructural characters were recorded by transmission electron microscopy. A peak in the feeding activity was observed toward dusk for an abundant June population, with 26% of cells with at least one food vacuole. Mechanisms of concurrent carbon acquisition were evident from the presence of chloroplasts with starch grains and food vacuoles within the same cell. Vacuole content could not be identified. In a preliminary 2-wk long simulated grazing experiment, a mixture of two hypothesized preys, Rhodomonas salina and Dunaliella tertiolecta, was offered to D. acuminata; the Dinophysis populations decreased steadily and at the same rate, whether food was present or not. The evaluation of the food vacuole frequency will be repeated in the coming season to verify the observed pattern, while grazing experiments will include a variety of food items and incubation conditions. Our current inability to successfully culture any photosynthetic Dinophysis limits ecophysiological approaches, either at the population or cellular level, to manipulation of field samples. Supported by National Institutes of Health Grant GM62126-01A1. [source]

Feeding behavior of lactating brown lemur females (Eulemur fulvus) in Mayotte: influence of infant age and plant phenology

AMERICAN JOURNAL OF PRIMATOLOGY, Issue 10 2006
Laurent Tarnaud
Abstract Altmann [Baboon Mothers and Infants, University of Chicago Press, 1980] and Dunbar and Dunbar [Animal Behavior 36:970,980, 1988] provided a model that predicts the amount of time spent feeding by lactating baboon females, as related to infant age. Dunbar's model further suggests that food quality affects the amount of time that females devote to feeding activity, and is predictable from rainfall and temperature data. In this study the model was tested with data recorded from births of the Mayotte brown lemur from four maternal dyads (Eulemur fulvus). This study also examines the correlation between female activity budget, quantities of fresh plant matter ingested, and suckling duration using data collected from focal animal samples on the mother,infant dyads. The relationships among rainfall, food supply, and food quality were also tested. It appears that female brown lemurs do not devote more time to feeding during the infant growth period. The data show that female brown lemurs increased their food intake during the early-lactating period when the frequency of suckling is the highest, and before infants begin to eat substantial amounts of solid foods. Thus, the frequency of feeding reflects the cost of lactation better than suckling duration. Furthermore, females did not appear to select foods according to their availability or rainfall levels. I hypothesize that the lack of convergence between lemur data and baboon observations is due to differences between their respective environments and their feeding ecology. These data also indicate that the most significant lactating cost for the brown lemur occurs during the early lactation period. Am. J. Primatol. 68:1,12, 2006. © 2006 Wiley-Liss, Inc. [source]

Animal behaviour and marine protected areas: incorporating behavioural data into the selection of marine protected areas for an endangered killer whale population

ANIMAL CONSERVATION, Issue 2 2010
E. Ashe
Abstract Like many endangered wildlife populations, the viability and conservation status of ,southern resident' killer whales Orcinus orca in the north-east Pacific may be affected by prey limitation and repeated disturbance by human activities. Marine protected areas (MPAs) present an attractive option to mitigate impacts of anthropogenic activities, but they run the risk of tokenism if placed arbitrarily. Notwithstanding recreational and industrial marine traffic, the number of commercial vessels in the local whalewatching fleet is approaching the number of killer whales to be watched. Resident killer whales have been shown to be more vulnerable to vessel disturbance while feeding than during resting, travelling or socializing activities, therefore protected-areas management strategies that target feeding ,hotspots' should confer greater conservation benefit than those that protect habitat generically. Classification trees and spatially explicit generalized additive models were used to model killer whale habitat use and whale behaviour in inshore waters of Washington State (USA) and British Columbia (BC, Canada). Here we propose a candidate MPA that is small (i.e. a few square miles), but seemingly important. Killer whales were predicted to be 2.7 times as likely to be engaged in feeding activity in this site than they were in adjacent waters. A recurring challenge for cetacean MPAs is the need to identify areas that are large enough to be biologically meaningful while being small enough to allow effective management of human activities within those boundaries. Our approach prioritizes habitat that animals use primarily for the activity in which they are most responsive to anthropogenic disturbance. [source]

The piercing-sucking herbivores Lygus hesperus and Nezara viridula induce volatile emissions in plants ,,

ARCHIVES OF INSECT BIOCHEMISTRY AND PHYSIOLOGY (ELECTRONIC), Issue 2 2005
Livy Williams III
Abstract Plant volatiles induced by herbivory are often used as olfactory cues by foraging herbivores and their natural enemies, and thus have potential for control of agricultural pests. Compared to chewing insects and mites, little is known about plant volatile production following herbivory by insects with piercing-sucking mouthparts. Here, we studied factors (insect life stage, gender, the role of salivary glands, and type of bioassay used for volatile induction) that influence the induction of plant volatiles by two agriculturally important hemipterans, Lygus hesperus and Nezara viridula. Feeding on intact cotton by virgin females of L. hesperus induced 2.6-fold greater volatile response compared to that induced by mated females, possibly due to increased feeding activity by virgin females. This plant volatile response was associated with elicitors present in the insect's salivary glands as well as to the degree of mechanical injury. Feeding injury by N. viridula females also increased volatile emissions in intact maize by approximately 2-fold compared to control plants. Maize seedlings injured by N. viridula emitted higher amounts of the monoterpene linalool, the sesquiterpenes (E)-,-caryophyllene, ,- trans -bergamotene, and (E,E)-,-farnesene, and the homoterpene (E,E)-4,8,12-trimethyl-1,3,7,11-tridecatetraene, but not amounts of green leaf volatiles, compared to uninjured plants. Emissions from intact maize injured by adult males were lower than those emitted by adult females of the same age and did not differ from those emitted by uninjured plants. Similarly, feeding by virgin female N. viridula followed by excision led to 64% higher quantities of volatiles compared to untreated plants. Volatile emission in excised plants, however, was considerably greater than in intact plants, suggesting that careful consideration must be given to bioassay design in studies of herbivore-induced plant volatiles. Salivary gland extracts of N. viridula led to sesquiterpene emissions approximately 2.5-fold higher than for controls, although no significant differences were observed for green leaf volatiles, monoterpenes, and homoterpenes. These results indicate that L. hesperus and female N. viridula feeding induce volatile production in plants, and that volatile production is affected by gender and life stage of the bug. Although oviposition and mechanical injury by stylets may increase release of volatiles, elicitors from salivary glands of L. hesperus and N. viridula also seem to play a role in the emission of plant volatiles. Arch. Insect Biochem. Physiol. 58:84,96, 2005. Published 2005 Wiley-Liss, Inc. [source]

Identification of the food sources of sympatric ghost shrimp (Trypaea australiensis) and soldier crab (Mictyris longicarpus) populations using a lipid biomarker, dual stable isotope approach

AUSTRAL ECOLOGY, Issue 8 2009
NICOLAS SPILMONT
Abstract Fatty acids (FAs) profiles and stable isotope signatures of the ghost shrimp, Trypaea australiensis and the soldier crab, Mictyris longicarpus were determined at an unvegetated sandbank of Southport (Gold Coast, Queensland, Australia), in November 2005 and February 2006. Additionally, the FAs composition of the faeces and feeding pellets of M. longicarpus and the surface sediment at the study site were also analysed. Trypaea australiensis was found to selectively feed principally on benthic diatoms, as revealed by the high contribution of the marker lipid (20:5 (n-3)) to tissue total FAs and the ,13C and ,15N isotopic signatures of shrimp tissues. Although the diet of T. australiensis did not change between the two sampling periods, the shrimps appeared to reduce their feeding activity in summer, presumably in relation to a restricted metabolism, as revealed by a decrease in the contribution of the microalgal markers in their tissues. The FAs composition of the tissues of the soldier crab indicated that bacteria and diatoms constituted the base of its diet (contributions of branched 15:0 and 17:0, 18:1 (n-7) and 20:5 (n-3)). However, the isotopic signatures of the crabs suggested that meiofauna may represent an intermediate link between the crab and these micro-organisms. [source]