Conditions Of Food Abundance Research Articles

Modeling the Bioenergetics and Life History Traits of Chironomus riparius–Consequences of Food Limitation

Chironomids have a number of characteristics that make them a useful group for investigating the impact of environmental and chemical stressors on their life cycle stages. It is crucial to first understand sensitivities to environmental factors and provide a basis for interpreting the results of toxicity tests. We focused on Chironomus riparius–one of the most studied species in aquatic toxicity tests—to understand the changes during the larval stage under conditions of food abundance and limitation. We developed a model based on Dynamic Energy Budget (DEB) theory, a framework to capture the entire life cycle of an individual under varying food and temperature conditions. Available information from this study and the literature pointed out that the first three larval instars are immature and the fourth larval instar is mature, during which the organism saves, in two phases, energy for essential processes occurring during the subsequent non-feeding stages. The model can successfully predict the observed prolonged fourth instar duration under food limitation, the times of life history events (e.g., pupation and emergence), and egg production. This model has the potential to be integrated with toxicokinetic–toxicodynamic models to study the effects of toxicants on a variety of biological traits.

Benefits, mechanisms, and risks of intermittent fasting in metabolic syndrome and type 2 diabetes.

One of the emergent nutritional strategies for improving multiple features of cardiometabolic diseases is the practice of intermittent fasting (IF), which consists of alternating periods of eating and fasting. IF can reduce circulating glucose and insulin levels, fat mass, and the risk of developing age-related pathologies. IF appears to upregulate evolution-conserved adaptive cellular responses, such as stress-response pathways, autophagy, and mitochondrial function. IF was also observed to modulate the circadian rhythms of hormones like insulin or leptin, among others, which levels change in conditions of food abundance and deficit. However, some contradictory results regarding the duration of the interventions and the anterior metabolic status of the participants suggest that more and longer studies are needed in order to draw conclusions. This review summarizes the current knowledge regarding the role of IF in the modulation of mechanisms involved in type 2 diabetes, as well as the risks.

Study on sumatran rhinoceros based on ecological game model

In this paper, the survival status of the sumatran rhinoceros was studied, the ecological game of the sumatran rhinoceros was put forward according to the critically endangered status, the differential dynamical system model of the sumatran rhinoceros and food was established, and the relationship between the parameters in the model and the land and environmental conditions was discussed. According to the value range of the four indicators, the ecological environment was divided into three conditions of food abundance, food shortage and critical state, so as to obtain the impact and requirements of the sumatran rhinoceros on the ecological environment. The results show that the sumatran rhinoceros lives in cycles under different land area conditions. Analysis from the perspective of the evolution of the ecological environment, the sumatran rhinoceros and food together form an ecological system, the abundant of food can cause sumatran rhinoceros populations, the number of the sumatran rhinoceros too much then can reduce the quantity of food, after reducing the number of the sumatran rhinoceros and will cause the increase in the number of food, this phenomenon is called ecological cycle, namely three environmental situation circulation phenomenon over time. Finally, according to the differential equation, migration is one of the ways that the sumatran rhino can continue to survive when the ecological environment changes.

Diet selection in overwinter caches of plateau zokor (Eospalax baileyi)

Subterranean herbivores affect the plant community by plant consumption and burrowing activities. However, diet selection of subterranean herbivores has not been studied in detail in complex natural fields, mainly for lack of an accurate method to determine diet species, frequency, and biomass. Plateau zokors' (Eospalax baileyi) caching habit for the long inclement winter makes it possible to solve this problem. We studied the diet composition and biomass in caches and vicinity of plateau zokors' burrow systems. We found that plateau zokors are dietary generalist but show a significant selection among the available food items, plant parts, functional groups, organ types, and habitats. These results suggested that plateau zokors strictly selected their diet and were able to adjust their foraging strategy according to the different conditions of food abundance and quality. Plateau zokors' selective foraging can directly reduce the proportion of toxicity forbs; plateau zokors can be recognized as an important element to influence the alpine meadow plant community and cattle husbandry.

ω-6 Polyunsaturated fatty acids extend life span through the activation of autophagy

Adaptation to nutrient scarcity depends on the activation of metabolic programs to efficiently use internal reserves of energy. Activation of these programs in abundant food regimens can extend life span. However, the common molecular and metabolic changes that promote adaptation to nutritional stress and extend life span are mostly unknown. Here we present a response to fasting, enrichment of ω-6 polyunsaturated fatty acids (PUFAs), which promotes starvation resistance and extends Caenorhabditis elegans life span. Upon fasting, C. elegans induces the expression of a lipase, which in turn leads to an enrichment of ω-6 PUFAs. Supplementing C. elegans culture media with these ω-6 PUFAs increases their resistance to starvation and extends their life span in conditions of food abundance. Supplementation of C. elegans or human epithelial cells with these ω-6 PUFAs activates autophagy, a cell recycling mechanism that promotes starvation survival and slows aging. Inactivation of C. elegans autophagy components reverses the increase in life span conferred by supplementing the C. elegans diet with these fasting-enriched ω-6 PUFAs. We propose that the salubrious effects of dietary supplementation with ω-3/6 PUFAs (fish oils) that have emerged from epidemiological studies in humans may be due to a similar activation of autophagic programs.

Abdominal obesity defined as a larger than expected waist girth is associated with racial/ethnic differences in risk of hypertension.

Waist circumference (WC) cut-points of > or =102 cm and > or =88 cm for men and women, respectively, representing abdominal obesity have been recommended for determining obesity related co-morbidities. However, these cut-points carry the component of generalised obesity estimated by body mass index (BMI). The aim of this investigation was to determine whether abdominal obesity free of the influence of overall heaviness is associated with increased risk of hypertension in a representative sample of white and black Americans. Data (n = 11114) from the Third US National Health and Nutrition Examination Survey were used in this investigation. Standardised residual values from the linear regression of WC on BMI were used to define abdominal obesity status. The risk of hypertension associated with abdominal obesity was estimated from the logistic regression model, adjusting for age, smoking and alcohol. We also estimated the public health consequences of abdominal obesity from the population attributable fraction of hypertension. Relative to white, black race/ethnicity was associated with approximately 1.8 and approximately 2.7 greater risk of hypertension in men and women, respectively, adjusting for abdominal obesity, age, smoking and alcohol consumption. Having larger than expected waist girths were associated with 1.58 and 1.39 increased risk of hypertension in black men and black women, respectively, adjusting for confounders. Population attributable risks of hypertension due to abdominal obesity were approximately 24.9% and 15.9%, in black men and black women, respectively. In Americans, hypertension is a public health problem that is closely linked to abdominal adiposity. An important research challenge therefore is to determine the best way to regulate body weight under conditions of food abundance. There is a need to clarify how lifestyle habits promote large waist sizes leading to abdominal adiposity and associated cardiovascular disease in the US, particularly among black Americans.

Paleolithic diets: a sceptical view

SummarySome anthropologists have suggested that humans are genetically determined to eat diets quite different from those of today. Very little human evolution has occurred in the past 15,000 years. However, diets have changed dramatically and in parallel with a shift in disease patterns from infectious diseases and diseases associated with nutrient deficiencies, to chronic degenerative diseases associated with excessive and unbalanced intake of energy and nutrients. This review examines some of the archaeological evidence relating to the diets of early man and other primates, and current hunter‐gatherer societies. Knowledge of the relative proportions of animal and plant foods in the diets of early humans is circumstantial, incomplete, and debatable and there are insufficient data to identify the composition of a genetically‐determined optimal diet. The evidence related to Paleolithic diets is best interpreted as supporting the idea that diets based largely on plant foods promote health and longevity, at least under conditions of food abundance and physical activity.

Ideal free distribution theory as a tool to examine juvenile coho salmon (Oncorhynchus kisutch) habitat choice under different conditions of food abundance and cover

We investigated the mechanisms affecting habitat choice by juvenile coho salmon (Oncorhynchus kisutch) in relation to the patchy distribution of food and cover. We tested the following hypotheses: (i) the distribution of juvenile coho, both between patches in a pool and between separate pools in a channel, corresponds numerically to the food input rate of those habitat patches as predicted by the "input-matching rule" of ideal free distribution (IFD) and (ii) the addition of instream cover, by increasing visual isolation among competitors, promotes input matching both within and between pools. We conducted our experimental work in artificial channels and we used two different types of cover, instream and overhead. In the absence of cover and with either no differences or relatively small differences in food abundance between patches, the spatial distribution of juvenile coho responded numerically to the input rate of food as predicted by the IFD. However, when differences in food abundance between patches were relatively large or cover was present, fish distributions consistently undermatched food input rate in the rich patch. Coho foraged in open patches away from cover within single pools but preferred pools with cover when choosing between separate pools. Several IFD models were used to examine the observed dispersion patterns.

Ideal free distribution theory as a tool to e×amine juvenile coho salmon (<i>Oncorhynchus kisutch</i>) habitat choice under different conditions of food abundance and cover

Ideal free distribution theory as a tool to e×amine juvenile coho salmon (<i>Oncorhynchus kisutch</i>) habitat choice under different conditions of food abundance and cover

Ecology of gyrfalcons, Falco rusticolus, in the central Canadian Arctic: diet and feeding behaviour

Diet and aspects of feeding behaviour in a population of gyrfalcons (Falco rusticolus) in the Northwest Territories were examined between 1984 and 1986. Three prey species, rock ptarmigan (Lagopus mutus), arctic ground squirrel (Spermophilus parryii), and arctic hare (Lepus arcticus), composed 96.5% of total prey biomass identified. Ptarmigan and hares were taken in May and June of all years (98.2% of biomass). Juvenile squirrels were used extensively in July and August of 1984 and 1985 but not in 1986, when squirrel production fell to almost zero; ptarmigan continued to be the dominant prey species throughout that summer. Because densities of breeding ptarmigan remained relatively constant during the study, but those of juvenile ground squirrels did not, it appeared that gyrfalcons responded functionally to varying availability of prey. Mean weight (250 g) of prey taken by male gyrfalcons was significantly less than the weight (330 g) of prey taken by females. As predicted by optimal foraging theory, average size of prey brought to the nest increased as time away from the nest increased. Conditions of food abundance were observed at most nests, suggesting that the amount of food available during the nestling period was not limiting production. We suggest that annual production is a function of spacing of pairs, which is set during courtship and prelaying, when prey availability is at its yearly low and when males must forage for both members of the pair. The fact that most gyrfalcon pairs initiated laying only after the spring arrival of migrating ptarmigan is consistent with this conclusion.

Relation between food consumption, growth and egg production in the tropical spiderCyrtophora cicatrosa (Araneidae, Araneae) under experimental conditions of food abundance and ration

Aspects of food utilisation, growth and egg production were studied inCyrtophora cicatrosa as a function of food abundance and ration. Restriction of ration resulted increased mortality, extension of nymphal period and prolongation of interoviposition period. Rates of feeding and conversion showed decreasing trend with reduced ration levels.C. Cicatrosa exhibited the following aspects of egg production: (a) larger the egg sac, higher the number of eggs present, (b) at optimum rearing conditions, such asad libitum ration at 27°C, the female produced large egg sacs and oviposited as many times as possible (c) age definitely affected the size of the egg sac, older the female, smaller the egg sac produced, (d) increased food consumption resulted in high egg production and (e) dry weight of the egg tends to be more or less constant.

Response of the ovenbird (Aves: Parulidae) to an outbreak of the spruce budworm

The response of the ovenbird (Seiurus aurocapillus) to an outbreak of the spruce budworm (Choristoneura fumiferana) was investigated in Algonquin Park, Ontario. Ovenbirds exhibited a functional response involving an unusual method of foraging for this species. The numerical response was based on smaller, more tightly packed territories and probably also on larger first and subsequent clutches. It is suggested that the great variability in clutch size of certain wood warblers (Parulidae) may indicate a tendency to lay successive clutches under conditions of food abundance.