Effect of Thallium on the Survival and Morphology of Tubifex Tubifex (Oligochaeta, Tubificidae)

Abstract

The present study aims to investigate the effect of Tl on the survival and morphology of Tubifex tubifex (sludge worm). For this purpose, Tl was applicated to the animals for 96 h of daily renewal tests at the following test concentrations: 0.005, 0.01, 0.025, 0.05, 0.1 and 0.5 mg/L(-1). Acute toxicity was analysed by the measurement of 96-h LC(50) value, and daily survival rates were analysed. Autotomy was evaluated as a criterion for sublethal toxicity. Morphological observations were conducted by binocular microscopic and scanning electron microscopic analyses. 96- h LC(50) and EC(50) values were determined to be 0.018 mg L(-1) and 0.0077 mg L(-1), respectively. The worms exhibit mortality starting from the lowest concentration (0.005 mg/L(-1)). When exposure time was extended, autotomized worms were observed to be deceased. Tl exposure resulted in the appearance of morphological alterations and adaptation responses in exposed worms. Constriction and/or loss of segments were observed in caudal region of most animals. There was a beaded appearance in the degenerating part of body. Mucus production was found to be increased. The results revealed that Tl is toxic to T. tubifex worms, even at lowest concentration (0.005 mg L(-1)).. This study represents the first assessment of Tl impact on T tubifex at laboratory conditions.