Aspidogastrea africanus Infections, comparative assessment of BTEX and heavy metals Bioaccumulation, and histopathological alterations as biomarker response in Chrysichthys nigrodigitatus (Lacépède, 1803) of Lekki Lagoon, Nigeria

The study was carried out on 120 randomly selected fresh specimens of Chrysichthys nigrodigitatus (males and females of different trophic levels) from Lekki lagoon, Lagos, Nigeria. The aim was to investigate the heavy metals and endoparasitic infection in the fish. We compared the impacts of both stressors on the liver and intestine of C. nigrodigitatus. Water samples were tested for pH, dissolved oxygen (DO), salinity, electrical conductivity, total dissolved solids using a multiprobe meter. Nitrate, nitrite, phosphorus, ammonia, total suspended solids and colour were measured using VR 5000 spectrophotometer. Alkalinity, acidity, biological oxygen demand (BOD) and chloride were measured via Titrimetry method. Chemical oxygen demand (COD) was measured via a closed reflux titration., and turbidity was measured via a VR 2010. Aspidogastrea africanus was the only parasitic infection detected in C. nigrodigitatus; though of low intensity. We also observed low heavy metal levels in the environmental media tested. However, the study showed that the liver and intestinal tissues of C. nigrodigitatus were slightly impacted by the stressors even at low levels. We therefore suspect synergy between Aspidogasrea infection and heavy metals toxicity. We recommend a further biomonitoring of the aquatic environment in order to ascertain the actual causative factors contributing to tissue injuries in the fish. Findings will help mitigate future aggravation of the tissue toxicity. Low levels of Aspidogastrea infection is an early prognostic information against outbreak of the disease in the aquatic environment. Keywords: Parasite intensity, Chrysichthys nigrodigitatus, Heavy metals, Histopathology, Stressor, Synergy