Model of copepod growth and development: moulting and mortality in relation to physiological processes during an individual moult cycle
Résumé
A mathematical model of copepod population dynamics coupling individual growth and development was tested. The results show in detail the effect of applying various hypotheses, particularly concerning the relationship between certain physiological processes (ingestion, egestion, excretion, oogenesis, etc.) and processes controlling the time course of abundance of individuals in each instar (mortality rate, moulting rate, reproduction). The model shows the changes in physiological processes (~ngestion, growth rate, etc.) at the individual level as a function of age within stage, and consequently the probability of moulting and death. If an indiv~dual remains for some time at one stage, its growth rate decreases, weight does not increase, the abil~ty to moult is lost and the probability of death is greater. In addition, the model glves the mean values of processes for the whole population, as could be obtained expenmentally, but it also provides an explanation of the variability of processes related to the population age structure. Finally, the results of this mathematical model led to an experimental test of the validity of the hypotheses put forward. The mathematical model can be used in all conditions, since it simulates values of processes constant in time as long as the external conditions are also constant, while remaining capable of expressing the internal dynamics of a population when the environment is suddenly perturbed.
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