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Institute for Sea Research, Texel, research on (own) energy require- ments in intertidal invertebrates has been initiated two years ago. The best known species now is Macoma balthica L. Macoma sampled from the tidal flats near Den Helder is kept in the laboratory under constant environmental conditions

M. Olmos, G. Van Snik, J.A. Planell and A. Casinos

. Therefore, the safety factor is generally high, except in tendons which store energy during locomotion. In view of these results, we wondered about the properties of tendons of other vertebrate groups. 2 Here, we present our results on both the stresses which could be applied by muscles in life in

J. Benzal

in autumn (STEBBINGS, 1966), though some may mate during spring (MOFFAT, 1922). 242 In Iberia, young are born in May and June (pers. obs.). Once adult size (forearm length) is attained, the bats must store enough energy to survive the first winter hibernation. Survival rate has been shown to be


). Migration and reproduction alternate in many insects. Both flight and reproduction make demands on the insects' energy resources. Between these activities there is an unstable equilibrium; it has been called the oogenesis-flight-syndrome OOHNSON, 1969). Insect hor- mones play an important role in the

H.J. VAN DER MEER and G. Ch. Anker

surface of the retina than a small twin does. This means that, in equally illuminated retinae, the large cones receive more energy per second than the smaller cones. One may presume that growth of visual cells includes an increase of functional cell-components like mitochondria and the membranes holding

C. Janse, J. Van Minnen, M. Van Der Roest and E.W. Roubos

it maximizes its fitness under a given set of constraints. As a consequence organisms keep a belance between functions like life span (defined by energy spent to maintenance), growth and reproductive activity. This implies that organisms contain (genetic) mechanisms which define life span, growth and

Peter Aerts

available strain energy in the contorted cartilage rod can be determined. By integrating the product of the required instantaneous moment M with the instantaneous work (i.e. the required work) and equalizing this to the amount of available energy (no energy dissipation is assumed) it is possible to

Nico M. Van Straalen

reflects the priorities put in the energy budget during life, may be subject to selection by environmental contaminants; this is exemplified by a study on isopods living in metal-contaminated sites. In conclusion, the biodiversity of ecotoxicological responses requires an evolutionary explanation and the

Peter Aerts

used in three ways: to change the kinetic energy of the element; to overcome the resistance of the water while it is moving, and the rest is trans- ported to the adjacent segments, similar to e.g. putting the shot, where energy is transmitted from the arm segments to the hand and ulti- mately to the

P.J. Drent, J.H. VAN BALEN, J.M. Tinbergen, J. DEN BOER-HAZEWINKEL, J.A.L. Mertens and A.J. CAVÉ

recruitment as a function of the size of the first brood. The predicted brood size shifts to a lower value close to the observed. 8. Measurements of energy content of female Great Tits in the incubation period in relation to temperature reveal a serious loss of fat reserves at low ambient temperatures