A Comparative Study of Respiration Rates of Some Aquatic Oligochaetes in Relation to Sublethal Stress

Aquatic oligochaete species selected on the basis of pollution tolerance or intolerance as determined from field studies were used to determine respiration rates under standard conditions, after exposure to sublethal levels of environmental variables (pH, salinity, temperature) or toxicants (Cd, Hg, NaPCP) alone or in pairs. Respiration rates, critical oxygen levels and degree of regulation were not correlated with field-determined tolerance to organic pollution. Stress factors caused increased or lowered respiration rate, loss of regulation (partial or total) and sometimes shifts in critical oxygen level. Regulation was improved in the face of some stresses. Combined stresses produced additional changes in respiration rates and regulation. These responses were complex, which makes them useful indicators of specific stress factors but also indicate complex mechanisms behind the observed changes.