Abstract

Diet quality and energy allocation influence an individual’s life-history traits by determining how much energy is available for processes such as growth and reproduction. One common method of assessing diet quality involves measuring gut length or size, which is typically inversely related to diet quality. However, this often requires animal sacrifice and time- consuming dissections. Similarly, many traditional bioenergetics models fail to capture the context-dependence of energy allocation, as these models rely on fixed energy allocation rules. One such rule is the κ-rule of dynamic energy budget theory, which assumes a fixed proportion (κ) of assimilated energy is always allocated to growth and maintenance. We conducted two studies aimed at improving the methodology of diet quality approximation and bioenergetics modeling, using the Asian shore crab Hemigrapsus sanguineus as a model system. In the first study, we tested whether external progastric region size predicts internal stomach size across latitude and time of year. If so, then external morphology could be used as a proxy for internal morphology, streamlining diet studies in crabs. We found that the width of the progastric region increased at a faster rate with body size than stomach width. In addition, the width of the progastric region followed different trends across sites and over time compared to stomach width. Our results therefore suggest that the progastric region may not be used as a proxy for stomach size variation across individuals. The second study investigated whether incorporating flexible energy allocation in a bioenergetics model could improve predictions of life-history traits such as clutch size. To answer this question, we developed a dynamic state variable model that identifies optimal limb regeneration strategies based on an individual’s characteristics. Our model predictions align with known patterns for this species, including increased regeneration effort with injury severity, a shift from reproduction to growth as consumption amount increases, and an increase in regeneration effort as regeneration progresses. Lastly, Monte Carlo simulations of individuals from a previous experiment demonstrate that flexible energy allocation successfully predicts reproductive effort, suggesting that this approach may improve the accuracy of bioenergetics modeling.

Degree

College and Department

Life Sciences; Biology

Rights

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