Effects of copper on energy metabolism and larval development in the midge Chironomus riparius

Abstract

When spiked in sediments, copper is known to reduce growth of Chironomus riparius larvae and the production of eggs by adult females. The aim of this work was to better understand the origin of these phenomena by studying the effects of copper using developmental and energetic biomarkers, such as changes in larval weight and age and changes in the levels of sugars and lipids. Four-day-old C. riparius larvae were exposed to nominal concentrations of copper of 0, 6.5, 12.5, 25 and 50 mg/kg of dry sediment (silica) in 0.6 l beakers. They were fed ad libitum and exposures were stopped at 7 and 9 days after the beginning of the tests. The larvae were weighed, sexed and aged. For each sex, the larvae belonging to the phases the most frequently found in the beakers were selected for dissection and measurement of energy reserves. The increase in the concentration of copper resulted in an increasing delay in larval growth in both sexes. Desynchronized development was observed, as shown by the increase in the number of individuals that remained in the third instar or early phases of the fourth instar, as well as by a reduction in age of males. Concerning energy reserves, the levels of sugars (glycogen, trehalose and glucose) in the dissected larvae remained almost constant among levels of exposure. In contrast, at the highest copper concentration (50 mg/kg), triglyceride levels suffered a slight reduction whereas the level of free glycerol significantly increased. It is concluded that selection of C. riparius larvae for both sex and age improves the relevance of some energy-yielding substrates as indicators of adverse physiological effects of copper.

Biochemical and morphological responses in Chironomus riparius (Diptera, Chironomidae) larvae exposed to lead‐spiked sediment

“…Further investigations are necessary to assess whether exposed larvae fed more to compensate for the energy used for detoxification mechanisms. In each condition tested, we noticed glycogen levels lower than those measured in C. riparius larvae by Servia et al . This could be partly because of a lower food supply in the conditions of our experiment.…”

Aedes aegypti pharate 1st instar quiescence affects larval fitness and metal tolerance

“…Detoxification, sequestration and elimination of metals and the neutralization of the oxidative stress associated with metal exposure are nutrient dependent processes (Calow, 1991; Servia, et al ., 2006). The exponential increase of Aa Mtn mRNA observed in larvae from new eggs was replaced by a modest linear increase in larvae that experienced a long quiescence.…”

Aedes aegypti pharate 1st instar quiescence: A case for anticipatory reproductive plasticity

“…Larval environmental metal stress resulted in reduced body mass and lipid reserves that were most likely responsible for reduced starvation tolerance in adults reared from both extended quiescence and short quiescence eggs, however the response was greater in the short quiescence condition. This overall reduction in performance in both phenotypes is most likely a result of the caloric cost of metal detoxification, sequestration and elimination (Mireji et al, 2010; Pook, et al, 2009; Servia, et al, 2006; Perez and Noriega, unpublished), but why the response was greater in short quiescence adults is unclear. We also witnessed a hormetic effect which was greater in adults reared from short quiescence.…”