Use of modeling to investigate potential feeding strategies of parasitic lampreys

Synopsis A quantitative energetics model of feeding and growth by parasitic lampreys was used to assess overall rates of net energy intake under alternate feeding strategies and varying host availability. Our early attempts to predict optimal feeding behavior focused on the duration of attachment to the host, but model simulations have revealed that optima over this variable may be so flat that, as in one case, a deviation of nearly 30% from the optimal attachment time results in only a 3% decrease in the rate of net energy intake. This may contribute to the great variability that appears characteristic of feeding by parasitic lampreys. Further simulations have suggested that, because host blood is to some extent a renewable resource, lampreys should extend host survival when alternate hosts are scarce by removing blood at reduced rates. In other words, maximization of instantaneous rate of net energy intake is not equivalent to maximization of long term gain. Thus, in predicting optimal lamprey feeding behavior, it is necessary to consider simultaneously both attachment time and rate of host blood removal. Behavioral or evolutionary adjustment of these variables can have important consequences with respect to lamprey growth rates, the functional response of lampreys to changing host densities, mortality rates of host populations, and the expression of other lamprey behavioral traits.