The mangrove ant, Camponotus anderseni, switches to anaerobic respiration in response to elevated CO2 levels

M.G. Nielsen, K.A. Christian

The small tree-living mangrove ant Camponotus anderseni is remarkably adapted for surviving tidal inundation. By blocking the nest entrance with a soldier's head, water intrusion into the nest cavity can be effectively prevented, but lack of gas-exchange caused extremely high concentrations of CO(2)(>30%) and very low O(2) concentrations (<1%). The O(2) uptake in experiments with CO(2) absorption showed a linear decrease until about 4%, whereas the O(2) uptake in chambers without absorbent showed a decrease with a different pattern, consisting of three parts. The first component of this decrease is a linear decrease to about 18%, which is the normal O(2) concentration in open natural nests. The second phase is an exponential decrease continuing to about 4% O(2), showing that the CO(2) concentrations have influence on the O(2) uptake. The final component is also exponential, but with a much smaller slope. The respiratory quotient (RQ) was 0.92 until CO(2) concentration increased to about 15-17%, and after that it showed a strong increase, which is due to the initiation of anaerobic respiration. Anaerobic respiration has not been demonstrated for social insects before, but it is not surprising that it is found in this ant species, which lives in the extreme conditions of a hollow twig in an inundated mangrove.