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last decade. However, data concern- ing Annelida are still scant and the picture of sterol metabolism in this phylum is very fragmentary. DALES, in his review on the energy metabolism in annelids (1969), points to the high content of sterols and sterolesters in the oil of these animals and mentions

In: Netherlands Journal of Zoology

between parasite and host leads to the inability of a parasite to regulate in the population dynamical sense. Under certain circumstances, one can envisage a system in which the parasite has to invest so much of its "energy" in non-reproductive efforts that its rate of increase drops below that of its

In: Netherlands Journal of Zoology

expansion, gains strain energy (due to tor- sion of the rostral free dental part of the meckelian rod). This stored strain energy is sufficient to restore the initial medial inclined position of the articular coulter area during suspensorial adduction. The energy is delivered by the opening mechanisms of

In: Netherlands Journal of Zoology

and their derivatives form a long series: movement, velocity, acceleration, vi- bration, force, momentum, work, power, potential and kinetic energy, friction, elasticity, viscosity, stress, strain, tensile strength, compressive strength, impact strength, heat parameters, conductivity, electric ac

In: Netherlands Journal of Zoology

serotinus close to the colony studied by CATTO et al. (1996). 408 Lactation is more energy demanding than pregnancy in bats (AN- THONY & KUNZ, 1977). Because the abundance of night-flying insects peaks after dusk and females must come back to suckle their young (SWIFT, 1980), bats emerge earlier to

In: Netherlands Journal of Zoology

-experimental analyses? Is it necessary or desirable to have hypotheses on adaptive changes when one wishes to reconstruct phylogenies? ALEXANDER (1967) views an adaptation as a gain in structurally incorporated energy by performing activities which are necessary to keep the organism in a particular environment. By

In: Netherlands Journal of Zoology

increasing the permeability to water and ions of the gill epithelium and by inhibition of the ion exchange activity of the chloride cells. The compensatory responses of the fish will significantly increase the energy required for maintenance of water and ion homeo- stasis, and this will result in reduced

In: Netherlands Journal of Zoology

the control of galactogen and glyco- gen metabolism is presented. INTRODUCTION GODDARD & MARTIN ( 1966) and EMERSON (1967) concluded that the metabolism of pulmonate snails is carbohydrate orientated: they depend for their energy requirements on carbohydrates. In Helix po- matia VON BRAND (1931

In: Netherlands Journal of Zoology

, 1962), and ide (PRECHT, 1964; JANKOWSKY & KORN, 1965); and in liver tissue of rainbow trout (EVANS et al., 1962) and goldfish (KANUN- GO & PROSSER, 1959). The activity of a number of enzymes playing a role in energy metabolism shows compensation for changes in acclim- ation temperature, e.g. the

In: Netherlands Journal of Zoology

serves primarily for the design of models, and secondarily as the idea of minimal consumption of mass and material and a minimal, relative consumption of energy and material for development. Can we say the same for deductive models in ecology? I shall restrict the discussion to the design of models for

In: Netherlands Journal of Zoology