Effect of alkaline pH on fungal resistance, total protein and total lipids of <i>Clarias gariepinus</i> skin mucus

Abstract

The effect of alkaline pH on fungal resistance, total protein, and total lipids on the skin mucus of Clarias gariepinus was investigated. C. gariepinus in renewal static bioassay were subjected to alkaline pH, alkaline + buffer solution, for comparison with fish from control. Antifungal activities of mucus from treatments and control fish were determined using a sensitivity test. Mucus was analyzed for total protein and total lipid contents using the Kjeldahl method and Soxhlet extractor respectively. Zones of inhibition were used to determine the sensitivity of mucus against fungal isolates. Fungi isolated were Aspergillus flavus, Aspergillus niger, Mucor mucedo, Rhizopus stolonifer, and Penicillium species. C. gariepinus mucus from treatments and control exhibited antifungal activity against fungal isolates. Mucus of C. gariepinus from control had higher zones of inhibition as compared with treatments. M. mucedo with 19.4mm zone of inhibition was more sensitive (P>0.05) to the antifungal activity of C. gariepinus. A. niger had significantly (P<0.05) lower zones of inhibition in alkaline pH. Total protein (30.65%) and total lipid (8.23%) were highest in alkaline pH mucus (P>0.05). This study shows that alkaline pH probably reduces the antifungal activity of C. gariepinus mucus and may elicit less resistance to fungal species.