DEPARTMENT OF ANIMALAND ENVIRONMENTAL BIOLOGY

6PPD-quinone (6PPD-Q) is a transformation product of the tyre additive 6PPD. It enters aquatic systems through stormwater runoff and poses an emerging toxicological concern. This study examined the acute and sub-lethal effects of 6PPD-Q on Clarias gariepinus, a freshwater catfish commonly used in ecotoxicological studies. The objective was to determine the sensitivity of Clarias gariepinus to 6PPD-Q and to assess changes in haematological parameters as indicators of physiological stress. Juvenile Clarias gariepinus were exposed under laboratory conditions to a range of 6PPD-Q concentrations for 96 hours to evaluate acute toxicity, followed by sub-lethal exposure for haematological analysis. No mortality was recorded during the acute phase, indicating that the compound did not reach a lethal threshold within the tested concentration range. Sub-lethal exposure produced measurable haematological alterations. There was a significant decrease (P<0.05) in red blood cell count, haemoglobin concentration, and packed cell volume, suggesting anaemia and impaired oxygen transport. White blood cell counts increased, indicating immune response activation. These findings demonstrate that 6PPD-Q affects fish health at non-lethal levels, even when acute mortality is absent. This study highlights the ecological risk posed by 6PPD-Q in aquatic environments. Its persistence and sub-lethal toxicity underscore the need for environmental monitoring and regulation of tire-derived pollutants. Further research should address long-term exposure, tissue accumulation, and population-level impacts in freshwater ecosystems.

The morphometric analysis of Synodontis courteti and Chrysicthys walkeri was carried out in Ovia River, Edo State, Nigeria. A total of fifty-four specimens of the two species were sampled over a period of six months, June to November, 2024. Specimens were transported to the laboratory and morphometric indices such as Total Length (TL), Standard Length (SL), Head Length (HL), Body Weight (BW), Intestinal Length (IL) and Body Depth (BD)were assessed using standard methods. The standard length and body weight of S. courteti ranged from 11.3 to 17.6cm and 40 to 225g, while the standard length and body weight of C.walkeri ranged from 10 to 19.4cm and 40 to 100g.The growth coefficient (b) was between 1.539 and 0.980 for S. courteti and C. walkeri. Results showed that both species exhibited a negative allometric growth. The intestinal length of S. courteti ranged from 9 to 21.0 while the intestinal length of C.walkeri ranged from 7.2 to 13.2. Following standard gut-length relationship for feeding classification, (<100 carnivore and >100 omnivore), both species were classified as carnivores having ratios of 87.77% and 72.67% respectively.