Sublethal effects of polluted river sediments on Chironomus riparius larvae (Diptera, Nematocera) under different temperature and food conditions
Parren, P.; Janssens de Bisthoven, L.; Ollevier, F.P. (1993). Sublethal effects of polluted river sediments on Chironomus riparius larvae (Diptera, Nematocera) under different temperature and food conditions. Belg. J. Zool. 123(Suppl. 1): 54-55
In: Belgian Journal of Zoology. Koninklijke Belgische Vereniging voor Dierkunde = Société royale zoologique de Belgique: Gent. ISSN 0777-6276; e-ISSN 2295-0451, meer
Field populations of Chironomus riparius larvae in the river Laan (Dijle basin, Scheldt watershed) show high incidences of mentum deformities. These are most probably induced by heavy .metals and pesticides locked in the aquatic sediments. Temperature (13°C and 18°C) and food quantity (5mg and 30mg tetraphyl/larvae) were modulated in laboratory experiments in order to investigate whether these parameters do influence the inducement of deformities of instar 4 larvae (native from Laan imagines) reared in Laan sediments. As a control, the artificial substrate siliceous earth (celite) was used. The development rate was primarily modulated by temperature (start of emergence at 18°C: day 17 - 18; at 13°C: day 34 and 48). Only at 13°C, a depleted food regime did show a delaying effect on the start of emergence (30mg food/larvae day 34; 5mg food/larvae day 48). In the high food condition, larval mortality was independent of temperature. In the low food condition however, larval mortality was higher and even more pronounced at the lower temperature condition. At 18°C (in the high food regime), the percentage of larvae with deformed menta was comparable with the percentage found in natural populations (10%). In the low food condition this percentage was lower (6.6%). At 13°C, the deformity percentage reached control values. These results suggest that the metabolic rate of the larvae has a greater effect on the occurrence of deformities than the exposure time (temperature effect). Moreover, it seems that bioaccumulation is enhanced by a higher food quantity, as is attested by the deformity percentages. This however, implies that a significant fraction of the pollutants is accumulated after association with ingested food particles, hence through the gut wall. This is in accordance with data from Kranzberg (1).(1) G. KRANZBERG (1989). Hydrobiologia 188:497-506.
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