Histopathological Changes in Periwinkle (Tympanotonus fuscatus var. radula) Exposed to Graded Doses of Nickel

Abstract

The periwinkle Tympanotonusfuscatus var. radula was exposed to sublethal concentration (0.5, l, 2, 4 and 8mg/L) of
nickel in the laboratory for 30 days. The test was conducted using the Organization for Economic Cooperation and Development
(OECD) protocol #218 in a sediment medium. There were three replicates per treatment and 6 periwinkles per tank of nickel
concentration including control groups. There was high bioaccumulation of nickel in the test organism. It was observed that
bioaccumulation of nickel in T. fuscatusvar. radula increased with increase in concentration of the heavy metal. Histopathological
alterations were studied in the Kidney and Muscular foot of the T. fuscatus var. radula. Periwinkle exposed to lower concentrations of
toxicant (0.5mg/L) showed hyperchromatic nuclei while fatty changes occurred in the 1, 2 4 and 8 mg/L exposures in kidney. Necrosis
was observed in the highest concentrations (4mg/L and 8mg/L). For the muscular foot, it was found that periwinkle exposed to lower
concentrations of toxicant (0.5mg/L and 1mg/L) showed fatty changes while the periwinkle exposed to higher concentrations (2mg/L,
4mg/L and 8mg/L) showed excess fatty changes and hyperchromatic nuclei in the muscular foot. Brown deposits were observed
around the fringes of the foot. This result shows that nickel can cause histopathological changes inT. fuscatus var. radula. The
discharge of effluents containing heavy metals especially nickel should be discouraged as this could affect the health of the organism
and exacerbate the problem of global biodiversity loss.