TERATOGENIC AND GENOTOXIC RESPONSES OF LARVAL CHIRONOMUS-SALINARIUS GROUP (DIPTERA, CHIRONOMIDAE) TO CONTAMINATED SEDIMENT

Chironomids are important indicators of the effects of sediment-bound contaminants. However, cause-effect relationships between contaminant exposure and stress-related indicators other than growth and survival have not been demonstrated. In the laboratory, we conducted 10-d expos ures of Chironomus salinarius group Kieffer larvae to mixtures of cont aminated (Trenton Channel, Detroit River, MI) sediment diluted with un contaminated, formulated sediment (sand, sculptor's clay, and potting soil) in ratios of 1:0, 1:1, 1:3, 1:7, 1:15, and 0:1. Larvae were inoc ulated into either recently mixed sediments or those allowed to age fo r 7 d. Surviving larvae were examined for mouthpart (mentum) deformiti es. Giant chromosomes of the salivary glands were examined for reducti on in relative nucleolus diameter (RND). Proportions of larvae with me ntum deformities and of larvae with reduced RND increased linearly wit h each doubling of concentration of contaminated sediment. Deformities and RND reduction in individual larvae were independent responses. In cidences of deformities at low contamination doses were much greater f or recently mixed sediments than for more aged sediments. Sediment age did not affect incidence of reduced RND except in the most contaminat ed treatment. Mentum deformities and reduced RND are quantifiable subl ethal attributes reflecting stress responses to sediment contamination that can complement more traditional measures (survival and growth) i n chironomid sediment bioassays.