Effects of oil-related environmental pollutants on gonads of the freshwater leech Limnatis nilotica (Annelida, Hirudinea)

Abstract

The main objective of this study was to determine the association between exposure to a mixture of benzene, toluene, ethylbenzene, and xylene (BTEX) and reproductive toxicity in the freshwater leech Limnatis nilotica. It was observed that exposure to 1.4 and 2.8 mg L−1 BTEX had a significant effect on previtellogenic and vitellogenic oocytes, but no effect on oogonia or early oocytes. In the 1.4 mg L−1 treatment group, previtellogenic and vitellogenic oocytes were characterized by clumping and shrinkage of the cytoplasm. In the 2.8 mg L−1 treatment group, the effect was more severe and the number of degenerating oocytes increased. The oocytes were easily identified by the vacuolization of their cytoplasm and nuclei. Exposure to 1.4 mg L−1 BTEX affected spermatogenesis by damaging spermatogenic cysts. 2.8 mg L−1 BTEX treatment caused severe damage to spermatogenesis manifested by the complete loss of normal cysts. The histopathological effects were confirmed by the comet assay because DNA damage was detected in both ovarian and testicular cells and was BTEX dose-dependent. The greatest DNA damage was recorded at 2.8 mg L−1 of BTEX in both ovarian and testicular cells compared to the control.