PARENT SESSION
PT3 - Adaptation/Acquired Environmental Resistance
Tuesday, 19 November 2002
8:00 AM to 6:30 PM
Exhibit Hall

(P585) Development of Mercury Adaptation in an Aquatic Oligochaete Worm .

Vidal, Doris^*,1, ¹ Southern California Coastal Water Research Project, Westminster, California, USA

ABSTRACT- Development and persistence of mercury resistance in the aquatic oligochaete worm Tubifex tubifex was studied under laboratory conditions. Two separate populations of T. tubifex were raised for four generations in clean and mercury-contaminated sediments. Mercury tolerance was established by comparative mercury toxicity tests (water only). Control worms had a mean LC₅₀ of 0.18 mgL ^-1. Worms exposed to high levels of mercury in sediment had high mercury tolerance with a mean LC₅₀ of 1.40 mgL^-1. Increased tolerance was inherited by succeeding generations despite the absence of high levels of mercury in their sediment. Moreover, subsequent crosses between tolerant and less tolerant worms grown in control sediment resulted in offspring with high mercury tolerance when compared to reference worms, thereby demonstrating adaptation as a result of several generations exposed to mercury. The LC₅₀ for worm descendants resulting from this cross was 1.39 mgL^-1. The tolerance developed by T. tubifex was rapid and the result of genetic adaptation to sublethal mercury exposure. Development of contaminant resistance and adaptation may be common phenomena in aquatic benthic invertebrates; toxicity tests with naïve organisms may not provide an accurate representation of the resistance of native populations.

Key words: Adaptation, Metals, Worms, Toxicity Test