Journal Article

Patterns of Fluctuating Asymmetry and Shape Variation in Chironomus riparius (Diptera, Chironomidae) Exposed to Nonylphenol or Lead

Branchu, Philippe, Arambourou, Hélène, Beisel, Jean-Nicolas, Debat, Vincent

2012

Overview

Deformities and fluctuating asymmetry in chironomid larvae have been proposed as sensitive indicators of biological stress and are commonly used to assess the ecological impact of human activities. In particular, they have been associated in Chironomus riparius, the most commonly used species, with heavy metal and pesticide river pollution. In this study, the effect of lead and 4-nonylphenol on mouthpart morphological variation of Chironomus riparius larvae was investigated by traditional and geometric morphometrics. For this purpose, first to fourth instar larvae were exposed to sediment spiked with lead (from 3.0 to 456.9 mg/kg dry weight) or 4-NP (from 0.1 to 198.8 mg/kg dry weight). Mentum phenotypic response to pollutants was assessed by four parameters: (1) the frequency of deformities, (2) fluctuating asymmetry of mentum length, (3) fluctuating asymmetry of mentum shape and (4) the mentum mean shape changes. Despite the bioaccumulation of pollutants in the chironomid's body, no significant differences between control and stressed groups were found for mouthpart deformities and fluctuating asymmetry of mentum length. Slight effects on mentum shape fluctuating asymmetry were observed for two stressed groups. Significant mean shape changes, consisting of tooth size increase and tooth closing, were detected for lead and 4-NP exposure respectively. Those variations, however, were negligible in comparison to mentum shape changes due to genetic effects. These results suggest that the use of mentum variation as an indicator of toxic stress in Chironomus riparius should be considered cautiously.

• Publisher: Public Library of Science,Public Library of Science (PLoS)
• Subject: Agrochemicals / Alkylphenols / Analysis / Animals / Aquatic insects / Asymmetry / Bioaccumulation / Biological Assay / Biological stress / Biology / Body Patterning - drug effects / Chironomidae - drug effects / Chironomidae - metabolism / Chironomus / Chironomus riparius / Conservation biology / Defects / Deformation effects / Earth Sciences / Ecological monitoring / Ecology / Environment / Environmental Monitoring / Evolution / Exposure / Fluctuating asymmetry / Genetic effects / Geologic Sediments / Heavy metals / Human influences / Laboratories / Larva - physiology / Larvae / Lead / Lead - chemistry / Metals, Heavy - chemistry / Micropterus salmoides / Morphology / Morphometry / Nonylphenol / Organisms / Pesticides / Pesticides - chemistry / Phenols - chemistry / Pollutants / Pollution / Pollution effects / Rivers / Sediments / Sediments (Geology) / Stream pollution / Stress (physiology) / Teeth / Temperature / Time Factors / Toxicology / Trends / Water Pollutants, Chemical - chemistry / Water pollution