A general model for effects of temperature on ectotherm ontogenetic growth and development

Abstract

The temperature size rule (TSR) is the tendency for ectotherms to develop faster but mature at smaller body sizes at higher temperatures. It can be explained by a simple model in which the rate of growth or biomass accumulation and the rate of development have different temperature dependence. The model accounts for both TSR and the less frequently observed reverse-TSR, predicts the fraction of energy allocated to maintenance and synthesis over the course of development, and also predicts that less total energy is expended when developing at warmer temperatures for TSR and vice versa for reverse-TSR. It has important implications for effects of climate change on ectothermic animals.Keywords: development rate; ectotherm development; energy budget; growth rate; temperature size rule The rates of ontogenetic growth and development are not exceptions. Ectothermic animals develop faster at warmer temperatures [1], and they usually mature at smaller body sizes-as much as 20 per cent smaller for a 108C temperature increase. This phenomenon has been called the 'temperature size rule' (TSR) [2]. Like most biological 'rules', however, there are exceptions, including welldocumented cases of the reverse-TSR, where the mature body sizes are larger at higher temperatures. Different compilations give about 15 per cent (13-17%) of reverse-TSR cases [2,3].Here, we develop a simple model for the effects of temperature on ontogenetic development of ectothermic animals. The model extends an earlier model for allocation of energy and biomass to growth on endotherms [4] by explicitly incorporating the temperature dependence of the rate of development and the rate of somatic growth. Any imbalance in these two rates results in either the TSR or reverse-TSR, depending on which process is more sensitive to temperature. The model predicts the fractions of energy allocated to maintenance and biomass synthesis at a given developmental stage, including the total quantity of energy expended during

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Testing Metabolic Theories

“…Under such a formulation, maturity and maximum size are reached simultaneously. Zuo et al (2011) recently included the potential for different temperature dependencies for differentiation and growth in the WBE growth model, such that the relative amounts of energy allocated to these processes could vary with temperature. Differentiation and growth then compete.…”

Higher temperature exacerbates the impact of sediments on embryo performances in a salmonid

“…In ectotherms (i.e. most aquatic organisms), temperature directly influences metabolism, development and growth rates and energy allocation to maintenance and synthesis, and subsequently determines body size and age at maturity [5]. Temperature also drives major physico-chemical processes, including the solubility of gases such as oxygen.…”