A65 Effects of Contaminants on Collective Systems

Topic

Chemical contaminants, such as neonicotinoids, affect each insect in the colony individually; however, the cumulative effect of this individual impact can ultimately lead to the collapse of the entire colony—a phenomenon known as Colony Collapse Disorder.

Within each insect, the amount of accumulated contaminant is determined by the balance between two opposing processes: absorption—which occurs whenever the insect comes into contact with contaminated flowers or soil—and elimination, achieved by the insect itself through its enzymatic detoxification system. The faster the insect absorbs the contaminant relative to its ability to eliminate it, the greater the amount that accumulates within its body.

The contaminant accumulating in this way is not distributed evenly throughout the insect's body; instead, it concentrates particularly in the nervous system, where it inhibits the nicotinic acetylcholine receptors required for normal nervous system function.

This inhibition of the insect's nervous system has two distinct consequences at the colony level. The first is the inhibition of recruitment: the colony loses the ability to mobilize foragers toward newly discovered food sources, and this reduced mobilization diminishes the flow of energy entering the colony.

The second consequence—even more critical than the first—is navigation failure: foragers exposed to the contaminant become unable to find their way back to the hive. Each forager that fails to return represents a permanent loss to the colony, as that adult insect is no longer available to contribute in any way.

Both consequences—the loss of energy flow and the permanent loss of foragers—ultimately manifest in the colony's bottom line: the balance between its contaminant-induced mortality rate and its natural growth rate. As long as the colony's growth rate manages to outpace that induced mortality, the colony is sustained; however, once the induced mortality exceeds the growth rate, the colony's size begins to decline exponentially, eventually leading to functional collapse. Ultimately, the speed at which this collapse occurs depends on the extent to which the pollutant-induced mortality exceeds the colony's natural growth rate.

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