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Investigating metabolic acceleration in dynamic energy budget models of copepods

Josef Koch (UGent) , Colin Janssen (UGent) and Karel De Schamphelaere (UGent)
(2018)
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Abstract
Copepods form an essential part of marine ecosystems and constitute a large portion of animal biomass on earth. Moreover, their small body size and short life cycle make them convenient test organisms in ecotoxicity studies. Beside acute toxicity, multiple works in the past focused on chronic life history effects of chemicals in copepods. Unfortunately, we usually lack a mechanistic explanation of observed effects which is required for realistic laboratory-to-field extrapolations. Models rooted in Dynamic Energy Budget (DEB) theory can help to evaluate sublethal toxicity data in terms of effects on the energy household of an animal. Although DEB models for new species are usually easily parameterised, the copepod life history shows distinct deviations from the ‘standard DEB model’ requiring further investigation. While some authors presume metabolic acceleration from birth until puberty, others suggest a von Bertalanffy growth curve which is truncated at the final moult. In this study we parameterised the two typified DEB models ‘abp’ (metabolic acceleration from birth to puberty) and ‘sbp’ (standard von Bertalanffy growth from birth to puberty) for the harpacticoid copepod Nitocra spinipes to investigate metabolic acceleration in copepods. As no high-quality data on length over time were available for N. spinipes, we performed a growth experiment over 28 days. Additional data from literature were used to aid the parameter estimation. Submodels for food (Holling’s type II functional response) and temperature dependency (Arrhenius temperature correction) were calibrated on development time and reproduction data. While isomorphic growth is commonly assumed in DEB studies, it does not hold true for N. spinipes which grows more slender in the course of its development. Hence, we used the square root of the top view area as a length measure to scale with the cubic root of structural volume in length-to-volume conversions. Both models abp and sbp showed good fits to the given data. Overall, abp predicted the data slightly better compared to sbp with a mean relative error of 0.063 vs. 0.076 in sbp. However, we do not regard this difference clear enough to unequivocally confirm or reject metabolic acceleration in copepods. More detailed data on N. spinipes and other copepods are needed to reveal the most accurate model for the copepod life history. That said, both models are promising tools for the evaluation and extrapolation of toxicity data in N. spinipes.

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Citation

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Chicago
Koch, Josef, Colin Janssen, and Karel De Schamphelaere. 2018. “Investigating Metabolic Acceleration in Dynamic Energy Budget Models of Copepods.” In .
APA
Koch, J., Janssen, C., & De Schamphelaere, K. (2018). Investigating metabolic acceleration in dynamic energy budget models of copepods. Presented at the SETAC Europe 28th Annual Meeting.
Vancouver
1.
Koch J, Janssen C, De Schamphelaere K. Investigating metabolic acceleration in dynamic energy budget models of copepods. 2018.
MLA
Koch, Josef, Colin Janssen, and Karel De Schamphelaere. “Investigating Metabolic Acceleration in Dynamic Energy Budget Models of Copepods.” 2018. Print.
@inproceedings{8625068,
  abstract     = {Copepods form an essential part of marine ecosystems and constitute a large portion of animal biomass on earth. Moreover, their small body size and short life cycle make them convenient test organisms in ecotoxicity studies. Beside acute toxicity, multiple works in the past focused on chronic life history effects of chemicals in copepods. Unfortunately, we usually lack a mechanistic explanation of observed effects which is required for realistic laboratory-to-field extrapolations. Models rooted in Dynamic Energy Budget (DEB) theory can help to evaluate sublethal toxicity data in terms of effects on the energy household of an animal. Although DEB models for new species are usually easily parameterised, the copepod life history shows distinct deviations from the ‘standard DEB model’ requiring further investigation. While some authors presume metabolic acceleration from birth until puberty, others suggest a von Bertalanffy growth curve which is truncated at the final moult. In this study we parameterised the two typified DEB models ‘abp’ (metabolic acceleration from birth to puberty) and ‘sbp’ (standard von Bertalanffy growth from birth to puberty) for the harpacticoid copepod Nitocra spinipes to investigate metabolic acceleration in copepods. As no high-quality data on length over time were available for N. spinipes, we performed a growth experiment over 28 days. Additional data from literature were used to aid the parameter estimation. Submodels for food (Holling’s type II functional response) and temperature dependency (Arrhenius temperature correction) were calibrated on development time and reproduction data. While isomorphic growth is commonly assumed in DEB studies, it does not hold true for N. spinipes which grows more slender in the course of its development. Hence, we used the square root of the top view area as a length measure to scale with the cubic root of structural volume in length-to-volume conversions. Both models abp and sbp showed good fits to the given data. Overall, abp predicted the data slightly better compared to sbp with a mean relative error of 0.063 vs. 0.076 in sbp. However, we do not regard this difference clear enough to unequivocally confirm or reject metabolic acceleration in copepods. More detailed data on N. spinipes and other copepods are needed to reveal the most accurate model for the copepod life history. That said, both models are promising tools for the evaluation and extrapolation of toxicity data in N. spinipes.},
  author       = {Koch, Josef and Janssen, Colin and De Schamphelaere, Karel},
  language     = {eng},
  location     = {Rome},
  title        = {Investigating metabolic acceleration in dynamic energy budget models of copepods},
  url          = {http://dx.doi.org/10.13140/RG.2.2.33906.04803},
  year         = {2018},
}

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