Comparative tolerance to low pH of three life stages of the crayfish Orconectes virilis

Abstract

The response of three life cycle stages of Orconectes virilis to acidification was investigated in the laboratory. Chronic lethality tests revealed that compared with 2-week-old stage III hatchlings, 2.5-month-old juveniles were seven times more tolerant to acid but only one-twentieth as tolerant as 2- to 3-year-old adults. Juvenile crayfish recovered following exposure to acid stress (pH < 3.5). Comparison of laboratory survival results with data from the literature concerning the magnitude and duration of chemical fluctuations indicates that lentic populations of O. virilis are not likely to decline as a result of episodic acid events. Nevertheless, gradual acidification of a lake to an average annual pH below 5.5 could result in eventual population extinction as a result of mortality of the young.