Effects of exposure to sulfur dioxide on the histology of fruit fly (Drosophila melanogaster) gonads and fat bodies.

Abstract

This study investigates the effect of larval exposure to sulfur dioxide on the histology of the Drosophila melanogaster gonads and fat bodies. The organs were examined through histological observation and measurement of testes area, ovariole number and fat body area and compared with those of the unexposed controls. Among the SO2-exposed flies. delayed maturation of the gonads was indicated by greater numbers of irregular spermatogenic cells in younger stages and by the decrease in the content of the acidophilic yolk cytoplasm in the mature eggs. An increase in glycogen storage within the fat bodies was observed in the flies exposed to 0.4 ppm SO2 It was also found that larger fat bodies are observed among female flies than in males. The increase in stored glycogen may be a mechanism that will allocate more energy stores for somatic maintenance. Antioxidant enzymes may also be produced at greater levels during exposure at larval stages. These mechanisms can reduce the allocation of the resources for reproduction and cause the delay in spermatogenesis and egg maturation. Larger fat bodies in females can be related to increased rate of lipid synthesis necessary for oocyte formation. These alterations in histology are discussed in terms of how low levels of SO2 exposure during larval development can influence reproductive capability and subsequently the relative fitness of the species in the long run.