Fluctuating asymmetry and mentum gaps in populations of the midge Chironomus riparius (Diptera: Chironomidae) from a metal-contaminated river

• Published in: Environmental toxicology and chemistry 1998-10, Vol.17 (10), p.1999-2005
• Main Authors: Groenendijk, D, Zeinstra, L.W.M, Postma, J.F
• Format: Article
• Language: English
• Subjects: Animal, plant and microbial ecology; Applied ecology; Biological and medical sciences; Chironomidae; Chironomus riparius; Developmental disturbances; ecotoxicology; Ecotoxicology, biological effects of pollution; Effects of pollution and side effects of pesticides on protozoa and invertebrates; Fluctuating asymmetry; Fundamental and applied biological sciences. Psychology; Mentum gaps; Metal pollution; population genetics; spatial variation; temporal variation; toxicology
• ISSN: 0730-7268; 1552-8618
• DOI: 10.1002/etc.5620171016

The developmental stability of both metal-exposed and nonexposed Chironamus riparius populations from the lowland River Dommel was investigated using fluctuating asymmetry (FA) and the incidence of mentum gaps. It was hypothesized that larval development was affected by the influx of metals, directly by chemical stress, as well as through inbreeding of metal-adapted and nonadapted specimens. Morphological parameters were therefore assessed in field-collected larvae and in clean, laboratory-cultured. first-generation (Fl) larvae Fluctuating asymmetry values and mentum gap incidence at contaminated field sites were significantly higher than at clean, upstream locations. Furthermore, FA values of clean, laboratory-cultured Fl larvae generally fell to reference values, indicating the direct effect of metal pollution on developmental aberrations. Mentum gaps were not observed in clean Fl cultures. Slightly elevated FA values were, however, still observed in clean Fl larvae from polluted locations downstream from the metal input. This residual disturbance was thought to reflect genetic stress emerging from interbreeding between metal-adapted and nonadapted specimens. Fluctuating asymmetry and mentum gaps together serve as a useful ecotoxicological marker for metal stress and, when combined with in situ studies and Fl cultures, allow for analysis of the response of animal populations to spatial and temporal gradients in metal exposure.