Energy budgets can explain body size relations
The size-dependence of some 20 physiological variables has been derived from a rather simple model for energy budgets. This nine parameter model is based on detailed observations on the growth and reproduction at varying food densities, and has the state variables size and storage. The size-dependence of some variables works out to be different for animals of the same species as opposed to animals of different species. The reproductive rate, for instance, tends to increase with size for animals of the same species, but to decrease with size for animals of different species. This is because the parameter values are constants within a species, but vary in a size dependent manner for animals of different species. Although growth at constant food density is assumed to be of the von Bertalanffy type, and routine metabolism to be proportional to size, respiration turns out to be about proportional to size to the power 3/4, both within and between species. The value of about 3/4 has frequently been found, but it has always been thought to be incompatible with von Bertalanffy growth.
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Cited by (192)
Standard dynamic energy budget model parameter sensitivity
2023, Ecological ModellingThe Dynamic Energy Budget model describes energy and mass balance in living organisms. It has found many applications in biological and ecological sciences. The model parameters can be connected to a single underlying biological process, and this mechanistic approach is helpful in understanding how complex biological systems work. However, the large number of model parameters makes it difficult to estimate their value, especially from data limited only to adult growth and reproduction at abundant food and constant temperature. Therefore, in this study, the sensitivity of the model solution to primary parameter values and the sensitivity of parameters to the perturbation in the data were analyzed. It was shown that the first-order sensitivity coefficients are different for each of the analyzed primary parameters and depend on their values and configuration in the equation. The sensitivity of parameters to data changes across analyzed time intervals, reaching minima and maxima. Moreover, the influence of each data point is smaller with an increasing number of data points. The recognition of the impact of parameters on the model solution, as well as the identification of data points with the strongest influence on estimates, can be helpful in experimental design and evaluation of the model.
The comparative energetics of the chondrichthyans reveals universal links between respiration, reproduction and lifespan
2022, Journal of Sea ResearchThe Add-my-Pet (AmP) collection of data on energetics and Dynamic Energy Budget (DEB) parameters currently contains 200 out of over 1100 extant species of chondrichthyans. This milestone in the compilation of data for this group led us to investigate: (1) do the characteristics that we reported in 2014 for 20 chondrichthyan species, relative to other fish, still hold (2) are novel patterns in properties revealed given the additional data and (3) do the four chondrichthyan subgroups (galean, squaleans, rays and chimaeras) differ in properties? We argue that a better understanding of these properties is key to sustainable management of the rapidly dwindling populations worldwide. Most of the inter-specific scatter in ultimate reproduction rate as function of ultimate body weight stems from differences in the mass of neonates as fraction of that of the mother, which is very high in chondrichthyans. The ultimate neonate mass production is found to be proportional to the ultimate respiration rate, with proportionality factor of 10 g/mol. The lifespan is found to be inversely proportional to weight-specific respiration, with a proportionality factor of 0.1 mol/g. The ultimate weight equals the life-time cumulated neonate mass production. These relationships also apply, with more scatter, to all 3000 animal species in the AmP collection. Sharks and rays were found to be more demand-species, contrary to ray-finned fish and chimaeras, which are supply species. Chimaeras also have that smallest weight at birth and precociality coefficient, compared to sharks and rays. Galeans grow much slower than squaleans and rays, but the chimaeras grow even slower. The lifespan equals 25 times the incubation time for chondrichthyans, but they are rather unique in this respect. Last but not least, we discuss the odd implications of recently published data on the energetics of the Greenland shark.
Identifying environmental drivers of shell shape and size variation in a widely distributed marine bivalve along the Atlantic Patagonian coast
2022, Zoologischer AnzeigerSince the impacts of climate change on marine benthic organisms are already detectable in many aspects, it is crucial to address the potential responses of marine organisms and their interactions with the environment. In particular, the study of phenotype traits along latitudinal gradients is a powerful tool for exploring species responses in a changing environment. This work aims to: i) Quantify the variation in shell shape and size of the stripped clam Ameghinomya antiqua (King, 1832) along a 1600 km latitudinal gradient in the Atlantic Patagonian coast using geometric morphometric (GM) methods; ii) Identify environmental effects on shell shape and size change, using generalized additive mixed models GAMMs; iii) Estimate the effect size of different factors influencing shell shape and size variation. The combination of GM and GAMM allowed the quantification and identification of previously unknown relationship between morphological axes of variation and environmental variables. Results suggest that salinity is the most important factor determining shell shape, mainly affecting the outline while temperature has a substantial but weaker effect. More elongated shells and longer ligaments are observed under (less favorable) conditions of low salinity and temperature. GAMM showed that chlorophyll-a concentration, used as a proxy for food supply, has the most significant effect on shell size, and shell growth does not match the somatic soft-tissue growth. These results may help to predict the effects of climate change on the size and shape of marine benthic species and bivalves in particular. Furthermore, they provide new insights for using shell size and shape as proxies for the reconstruction of past environments and climates.
Aggregations reduce winter metabolic rates in the diapausing ladybeetle Hippodamia convergens
2022, Journal of Insect PhysiologyEnergy conservation is linked to survival and fitness of overwintering ectotherms, and is particularly critical in winter. Although many insects overwinter individually, some form aggregations with conspecifics. Aggregations cause metabolic suppression in some insects, but the effect of aggregations on metabolic rates and energy use in overwintering aggregations remains underexplored. The convergent ladybeetle (Hippodamia convergens) overwinters in massive aggregations, making it an ideal system for testing the effect of aggregation size on metabolic rates in overwintering insects. We measured metabolic rates of beetle aggregations of 1, 10, 25, and 50 individuals using stop-flow respirometry across two ecologically relevant temperatures, and measured locomotor activity as one possible driver of group effects on metabolic rate. Metabolic rates per beetle decreased with increasing aggregation size at both temperatures, but was more pronounced at low temperatures. Metabolic rates scaled hypometrically with mass, with deeper response at cool temperatures. Activity decreased with aggregation size, but only at low temperatures. These results suggest that individuals within aggregations enter a deeper metabolically inactive state that single individual beetles cannot achieve, which is partly but not completely explained by a reduction in locomotor activity. This group strategy for energy conservation may provide an additional selective advantage for the evolution of large overwintering aggregations.
Multiple working hypotheses for hyperallometric reproduction in fishes under metabolic theory
2020, Ecological ModellingHyperallometric reproduction, whereby large females contribute relatively more to the renewal of the population than small females, is purported to be widespread in wild populations, especially in fish species. Bioenergetic models derived from a sufficiently general metabolic theory should be able to capture such a relationship but it was recently stated that no existing models adequately capture hyperallometric reproduction. If this were true it would seriously challenge our capacity to develop robust predictions of the life history and population dynamics in changing environments for many species. Here, using the European sea bass (Dicentrarchus labrax) as a test case, we demonstrate multiple ways that hyperallometric reproduction in a population may emerge from the Dynamic Energy Budget (DEB) theory, some inherently related to the metabolism and life history and others related to plastic or genetically based intraspecific variation. In addition, we demonstrate an empirical and modelled hypoallometric scaling of reproduction in this species when environment is controlled. This work shows how complex metabolic responses may underlie apparently simple relationships between weight and reproduction in the wild and provides new and testable hypotheses regarding the factors driving reproductive scaling relationships found in the wild.
The use of augmented loss functions for estimating dynamic energy budget parameters
2020, Ecological ModellingWe propose an extension of a parameter-free loss function for the estimation of Dynamic Energy Budget parameters for a set of related species that is symmetric in the role of data and predictions. The extension allows that particular parameters might vary, but not by much, among species, while the degree of variation is controlled by weight coefficients. We discuss the choice of these coefficients and illustrate the application with an example of two species of catfish, with their mutual hybrids. In our simultaneous parameter estimation for this example, we could reduce the variation in a parameter, here the energy conductance, substantially with a minor effect on the goodness of fit. We selected this parameter among the ones that varied, because its value was poorly determined by the data. We discuss this example in some detail. The software for implementing this augmented loss function has been implemented in the available software DEBtool_M on Github (www.github.com/add-my-pet/DEBtool_M).
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Present address: Biological Laboratory, Free University, P.O. Box 7161, 1007 MC Amsterdam, The Netherlands.