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Food Requirements (food + requirement)
Selected AbstractsSurvival and development of five species of cyclopoid copepods in relation to food supply: experiments with algal food in a flow-through systemFRESHWATER BIOLOGY, Issue 9 2005ULRICH HOPP Summary 1. Cyclops spp. generally develop and grow during favourable food conditions in spring and undergo a diapause in summer, while Acanthocyclops robustus, Mesocyclops leuckarti and Thermocyclops crassus develop and grow in summer when they face poorer food conditions and more competition from Cladocera. Since nauplii are the bottleneck in copepod development, we tested the hypothesis that Cyclops abyssorum and C. vicinus nauplii have higher food requirements for survival and development than the nauplii of A. robustus, M. leuckarti and T. crassus. We also tested survivorship and development from hatching to adulthood. 2. Survivorship and development of the copepods was studied in a flow-through system using five concentrations of the phytoflagellate Chlamydomonas reinhardtii in the range from 1 × 104 to 4.5 × 105 cells mL,1 (approximately 0.5,22.5 mg C L,1). 3. Nauplii of both species of Cyclops died at intermediate to low (C. abyssorum) and low (C. vicinus) food concentrations, while nauplii of A. robustus, M. leuckarti and T. crassus survived at all concentrations. 4. The negative effects of low food concentration were also reflected in development. In C. abyssorum and C. vicinus, development duration increased at low food concentration while development was much less affected in A. robustus and T. crassus. Mesocyclops leuckarti was intermediate between Cyclops spp. and A. robustus/T. crassus, with an increase in development duration at the lowest food concentration. 5. Our results support the hypothesis that summer diapause in Cyclops spp. has developed as a strategy to avoid a food bottleneck for nauplii. [source] Effects of the non-indigenous cladoceran Cercopagis pengoi on the lower food web of Lake OntarioFRESHWATER BIOLOGY, Issue 12 2003Corey L. Laxson Summary 1. In North America, the invasive predatory cladoceran Cercopagis pengoi was first detected in Lake Ontario. We explored the impact of Cercopagis on the lower food web of Lake Ontario through assessments of historical and seasonal abundance of the crustacean zooplankton, by conducting feeding experiments on the dominant prey of the invader, and by estimating its food requirements. 2. Between 1999 and 2001, a decrease in the abundance of dominant members of the Lake Ontario zooplankton community (Daphnia retrocurva, Bosmina longirostris and Diacyclops thomasi) coincided with an increase in the abundance of Cercopagis. Daphnia retrocurva populations declined despite high fecundity in all 3 years, indicating that food limitation was not responsible. Chlorophyll a concentration generally increased, concomitant with a decline in the herbivorous cladoceran zooplankton in the lake. 3. Laboratory experiments demonstrated that Cercopagis fed on small-bodied species including D. retrocurva and B. longirostris. 4. Consumption demand of mid-summer populations of Cercopagis, estimated from a bioenergetic model of the confamilial Bythotrephes, was sufficient to reduce crustacean abundance, although the degree of expected suppression varied seasonally and interannually. 5. Predatory effects exerted by Cercopagis on the Lake Ontario zooplankton, while initially very pronounced, have decreased steadily as the species became established in the lake. [source] Copepod life cycle adaptations and success in response to phytoplankton spring bloom phenologyGLOBAL CHANGE BIOLOGY, Issue 6 2009HANNO SEEBENS Abstract In a seasonal environment, the timing of reproduction is usually scheduled to maximize the survival of offspring. Within deep water bodies, the phytoplankton spring bloom provides a short time window of high food quantity and quality for herbivores. The onset of algal bloom development, however, varies strongly from year to year due to interannual variability in meteorological conditions. Furthermore, the onset is predicted to change with global warming. Here, we use a long-term dataset to study (a) how a cyclopoid copepod, Cyclops vicinus, is dealing with the large variability in phytoplankton bloom phenology, and (b) if bloom phenology has an influence on offspring numbers. C. vicinus performed a two-phase dormancy, that is, the actual diapause of fourth copepodid stages at the lake bottom is followed by a delay in maturation, that is, a quiescence, within the fifth copepodid stage until the start of the spring bloom. This strategy seems to guarantee a high temporal match of the food requirements for successful offspring development, especially through the highly vulnerable naupliar stages, with the phytoplankton spring bloom. However, despite this match with food availability in all study years, offspring numbers, that is, offspring survival rates were higher in years with an early start of the phytoplankton bloom. In addition, the phenology of copepod development suggested that also within study years, early offspring seems to have lower mortality rates than late produced offspring. We suggest that this is due to a longer predator-free time period and/or reduced time stress for development. Hence, within the present climate variability, the copepod benefited from warmer spring temperatures resulting in an earlier phytoplankton spring bloom. Time will show if the copepod's strategy is flexible enough to cope with future warming. [source] Sanitary versus environmental policies: fitting together two pieces of the puzzle of European vulture conservationJOURNAL OF APPLIED ECOLOGY, Issue 4 2010Antoni Margalida Summary 1.,Between 1996 and 2000 the appearance of bovine spongiform encephalopathy swiftly became one of the most serious public health and political crises concerning food safety ever experienced in the European Union (EU). Subsequent sanitary regulations led to profound changes in the management of livestock carcasses (i.e. the industrial destruction of around 80% of all animal carcasses), thereby threatening the last remaining healthy scavenger populations of the Old World and thus contradicting the long-term environmental policies of the EU. 2.,Several warning signs such as a decrease in breeding success, an apparent increase in mortality in young age classes of vultures and an increase in the number of cases of vultures attacking and killing cattle, as well as a halt in population growth, suggest that the decrease in the availability of food resources has had harmful effects on vulture populations. 3.,Between 2002 and 2005, a number of dispositions to the EU regulations (2003/322/CE 2005/830/CE) enabled conservation managers to adopt rapid solutions (i.e. the creation of vulture restaurants) aimed at satisfying the food requirements of vultures. However, these conservation measures may seriously modify habitat quality and have indirect detrimental effects on avian scavenger populations and communities. 4.,Synthesis and applications.,Conservation managers and policy-makers need to balance the demands of public health protection and the long-term conservation of biodiversity. The regulations concerning carrion provisioning need to be more flexible and there needs to be greater compatibility between sanitary and environmental policies. We advocate policies that authorize the abandonment of livestock carcasses and favours populations of wild herbivores to help to maintain populations of avian scavengers. Conservation strategies should be incorporated into new European Commission regulations, which should be effective in 2011. [source] Should males come first?JOURNAL OF AVIAN BIOLOGY, Issue 6 2005The relationship between offspring hatching order, sex in the black-headed gull Larus ridibundus In birds with hatching asynchrony and sexual size dimorphism, chicks hatched earlier and later in the laying sequence usually suffer different mortalities due to uneven abilities to compete for food, especially in poor years. If sexes differ in vulnerability to environmental conditions, e.g., by having different food requirements due to differential growth rates, mothers can increase fitness by allocating sex according to the laying order, producing less vulnerable sex later rather than early in the clutch. By analysing variation in primary sex ratio using a PCR-based DNA technique, we tested this prediction in black-headed gull Larus ridibundus chicks where males may be the less viable sex under adverse conditions. The overall primary sex ratio of the population did not depart from parity. However, first hatched chicks were more likely to be males whereas last hatched chicks were more likely to be females. Both egg volume and hatchling body mass decreased with laying order irrespective of sex. Time of breeding had no effect on offspring sex or hatchling sex ratios. [source] Hunting strategies and foraging performance of the short-toed eagle in the Dadia-Lefkimi-Soufli National Park, north-east GreeceJOURNAL OF ZOOLOGY, Issue 3 2010D. E. Bakaloudis Abstract The foraging performance and the hunting strategies of foraging short-toed eagles Circaetus gallicus were studied in Dadia-Lefkimi-Soufli National Park during 1996,1998. A general linear model analysis showed that the eagle's hunting mode was related to wind velocity. At low wind speeds, the eagles more frequently soared and/or hovered, whereas on windy days, they hung more frequently than soared or hovered. Individuals appear to compensate for the high-cost foraging method (hovering) with a high capture rate or a low capture rate with low-cost foraging methods (soaring and hanging). In addition, their foraging activities exhibited two patterns. In the early (April) and late (September) breeding season, eagles foraged mainly during midday, while from May to August eagles foraged largely during the morning and a little during the afternoon, reflecting to some extent the diurnal activity of prey (reptiles) throughout the breeding season. Short-toed eagles tended to forage for longer as the breeding season progressed, peaking during August due to additional food requirements before autumn migration. Following a mixed foraging strategy throughout the breeding season, short-toed eagles increased their hunting efficiency, which may benefit increased breeding success and energy reserves for migration. [source] Developmental changes in the patterns of feeding in fourth- and fifth-instar Helicoverpa armigera caterpillarsPHYSIOLOGICAL ENTOMOLOGY, Issue 4 2000D. Raubenheimer Summary Data are presented for developmental changes in feeding behaviour within and across the fourth and fifth stadium of Helicoverpa armigera (Lepidoptera, Noctuidae) caterpillars fed nutritionally homogeneous semi-synthetic foods. We recorded the microstructure of feeding over continuous 12-h periods on consecutive days throughout the two stadia, and in one experiment recorded continuously for 21 h. Larvae in the two stadia showed the same general pattern of macro-events in feeding, including a similar duration of post-ecdysis fast, which was usually broken by consumption of the exuviae, and then a sustained period in which discrete meals on the experimental food were taken regularly. There were, however, some distinct differences in the patterns of meal-taking both between stadia and across different one-third time segments within stadia. Considering between-stadium differences, the proportion of time spent feeding differed significantly only in the last segment of the feeding period of the two stadia, with the value for the fourth-instar larvae being substantially greater than for fifth-instar larvae. As regards within stadium changes, the proportion of time feeding increased from the first to the second segment of both stadia. However, whereas the proportion of time feeding increased from the second to the final segment of the fourth stadium, it decreased across the same period in the fifth stadium. These patterns of changes in the proportion of time feeding within and between stadia, and their behavioural mechanisms (combination of meal durations and meal frequencies), can be explained only partially with reference to increasing food requirements with development. Three areas are identified where further study might help elucidate the reasons for the observed developmental changes in the microstructure of feeding: allometric constraint, the dynamic links between ingestion and post-ingestive processing, and ecological factors such as predation. [source] Contrary food requirements of the larvae of two Curtonotus (Coleoptera: Carabidae: Amara) speciesANNALS OF APPLIED BIOLOGY, Issue 2 2005P. Saska Abstract The larvae of carabids that are granivorous as adults can be granivorous, omnivorous or carnivorous. The differences in larval food preferences of Amara aulica and Amara convexiuscula, two closely related species of the subgenus Curtonotus, were studied. Survival and duration of development of non-diapausing first and second instar larvae were compared. The third instar larvae were not studied because they go into diapause prior to pupation. The larvae were fed diets consisting of insect larvae (Tenebrio molitor), seeds of Artemisia vulgaris, Tripleurospermum inodorum, Urtica dioica or Cirsium arvense and a mixed diet consisting of insect larvae and seed. Larvae of A. aulica required seeds for successful development, whereas those of A. convexiuscula developed on both an insect diet and seeds of Artemisia. The difference in larval food requirements facilitates the coexistence of these closely related species, which frequently share the same habitat. [source] | ||||||||||