Time-dependent modulation of post-hatch cortisol and antioxidant responses in Melanotaenia boesemani embryos exposed to potassium derived from banana peel ash extract

Responses of M. boesemani to potassium exposure

Abstract

Embryonic exposure to ionic disturbance can alter post hatch stress regulation in fish. This study examined whether immersion duration in potassium-rich banana peel ash extract affected endocrine and antioxidant responses in Melanotaenia boesemani. Embryos were immersed in a fixed potassium concentration of BPA extract (13.5 mg L^-1) for 15.5, 24, and 32.5 h, alongside untreated and KCl reference groups (three biological replicates per treatment). Cortisol, superoxide dismutase (SOD), and catalase (CAT) were quantified at 7 days post hatching, and survival was recorded at 60 days post-hatching. Data were analyzed using one-way ANOVA with Tukey HSD, Pearson correlation, and principal component analysis (PCA). All four endpoints (cortisol, SOD, CAT, and survival rate) differed significantly among treatments (p<0.05). Cortisol was significantly higher in all BPA-exposed groups than in both controls, reaching its highest numerical value at 24 h, although the three BPA-duration groups did not differ significantly from one another. SOD and CAT activities increased with BPA exposure, reaching their highest values at 24 h. CAT remained significantly elevated relative to the controls and the 15.5 h group at both 24 and 32.5 h, whereas SOD was significantly elevated relative to the controls and the 15.5 h group only at 24 h. SR declined progressively with increasing immersion duration and was lowest at 32.5 h. Cortisol correlated positively with SOD (r = 0.86) and CAT (r = 0.81), and SOD correlated strongly with CAT (r = 0.87). Survival rate was negatively correlated with cortisol (r = -0.59) and CAT (r = -0.75). PCA reduced the four variables into two components explaining 94.3% of total variance and separated BPA exposed groups from controls along a biomarker dominated axis. These results indicate a coordinated endocrine and antioxidant response following embryonic BPA exposure, but the magnitude of the biomarkers was not directly related to survival outcome. The highest biomarker responses at 24 h coincided with intermediate survival, while the lowest survival at 32.5 h occurred alongside declining biomarker levels. This dissociation indicates that immersion duration itself, independent of potassium concentration, is an important variable to consider when evaluating biomass-derived potassium sources for use during early developmental stages.