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A. Kortlandt

) and E. C. TOLMAN (1932) in particular who criticised this too simple chain-reflex scheme and added two other essential attributes to the then concept of instinct: Firstly, the notion of "appetite" or instinct-specific intrinsic "energy", here to be represented by E, which causes "fluctuations" or

J.M. Koolhaas, J.H. Strubbe and L. De Ruiter

perception of food and performance of feeding responses, and the VMH as a 'satiety centre', recording the energy content of the body and in- hibiting the LH as soon as energy exceeds the desired level (fig. 2). However, what satiety signals the VMH received was not yet clear. We shall now discuss how we

Carel Ten Cate

argumentation for nature conservation, or to assist in breeding endangered bird species. KEY WORDS: bird research, animal models, feeding mechanisms, energy allocation, visual system, behavioural development, vocal communication, song development. INTRODUCTION In general, birds are among the most conspicuous

G. Ernsting and J.A. Isaaks

springtails used in the present study were obtained from a mass culture in the laboratory. Only specimens from the range 0.45-0.55 mg fresh weight were offered to the beetles (dry weight = 0.22 fresh weight). In an energy budget analysis of the beetle (DE RUITER & ERNSTING, 1987) the energy value of this prey


). Little is known about the function of glycogen during embryogenesis. Energy production (LUDWIG et al., 1965 on Tenebrio) may be only one of its functions. Glycogen can be interconverted to pyruvate, thus anaerobically releasing energy during glycolysis. Pyruvate can be broken down aerobically to CO2 and

J.W.M. Osse

times that of air. It is to be expected that the limited amounts of energy and building molecules obtained from external feeding will successively serve the priorities for survival, growth and ongoing differentiation. BLAXTER (1988) provides a recent survey on the general scheme and the many varieties

G. VAN BEEK and J.P. Veldhuijzen

112 these body parts taken together represents only a small percentage of the total decrease (18%). The polysaccharides of the other body parts are mobilized readily (Fig. 3). Table I shows that these three body parts are very important as energy source during starvation, since the decrease in the

J.H. Van Balen and A.J. Cavé

broods of 8 young, from which he concluded that the extra energy required to keep a small brood warm is so large that a larger brood needs scarcely more food. MERTENS (1969) showed that the heat production per young (and consequently the energy requirements) depends on brood-size and temperature. He also

Vinod Sommandas, Vincent Van Ginneken, Marjolijn Onderwater, Guido Van Den Thillart and Paul Balm

when anaerobic metabolism becomes activated is not strictly deŽ ned among animals and will depend on factors such as respiration capacity, energy stores, and capacity for end product elimination of individuals. Therefore, an individual variation of the aerobic scope among animals may be expected. To

Jan G. Sevenster, Gerard Driessen and Jacintha Ellers

egg production (E) and life span (L), with L = T - aE. In this case, each additional egg produced directly decreases the energy reserves available for life span by an equal amount. Incorporating different shapes of trade-off functions may have important consequences for the predictions of evolutionary