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The Strathprints institutional repository is a digital archive of University of Strathclyde's Open Access research outputs. Strathprints provides access to thousands of Open Access research papers by Strathclyde researchers, including by researchers from the Physical Activity for Health Group based within the School of Psychological Sciences & Health. Research here seeks to better understand how and why physical activity improves health, gain a better understanding of the amount, intensity, and type of physical activity needed for health benefits, and evaluate the effect of interventions to promote physical activity.

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Growth and energy allocation in the deep-sea urchin Echinus affinis

Middleton, D.A.J. and Gurney, William and Gage, J.D. (1998) Growth and energy allocation in the deep-sea urchin Echinus affinis. Biological Journal of the Linnean Society, 64 (3). pp. 315-336. ISSN 0024-4066

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Abstract

Growth of regular echinoids, expressed as test diameter through time, generally shows a sigmoidal pattern. However, when urchin size is considered in terms of test volume we show that growth of the deep-sea echinoid Echinus affinis is ultimately linear, rather than saturating. We construct a simple allometric model of energy allocation that produces linear growth in volume in mature urchins by allocating an increasing proportion of net assimilate to reproduction. This model provides an excellent fit to the observed growth curve data. Data on gonad weight as a function of test diameter allow us to test the relationship between allocation to reproduction and urchin size predicted from the growth curve fit. Simultaneous fitting of the growth curve and gonad weight data allow us to consider a model where the allometry of net assimilation is allowed to vary. We investigate possible explanations for the fact that net assimilation appears to rise faster than linearly with weight in E. affinis. We conclude that strategic models of individual energetics provide a useful tool for the analysis of the limited data available on deep-sea populations.