<![CDATA[Background: Elevated temperature can disrupt embryonic development in ectothermic vertebrates by altering developmental progression, growth, and morphological integrity. Lycopene is a naturally occurring carotenoid with recognized antioxidant properties and may contribute to cellular protection under stressful conditions. Purpose: This study evaluated the effects of lycopene supplementation on developmental progression, larval body length, and morphological abnormalities in zebrafish (Danio rerio) exposed to acute heat stress. Method: A total of 240 viable zebrafish embryos were assigned to non heat stress (NHS; 28°C) or heat stress (HS; 30°C for 1 h) conditions. Each thermal condition comprised three treatments: control without lycopene (P1), 2 µL lycopene supplementation (P2), and 4 µL lycopene supplementation (P3), with four replicates per treatment. Embryonic development was monitored until 96 h post fertilization (hpf). Larval body length was measured using ImageJ, while morphological abnormalities were assessed microscopically. Body length data were analyzed using one-way ANOVA followed by the LSD post hoc test (p < 0.05). Results: Heat stressed larvae generally exhibited shorter body lengths than non heat stressed larvae, with significant overall differences among treatment groups (p < 0.05). Within the heat stressed groups, mean body length increased numerically from 3.10 mm in HSP1 to 3.28 mm in HSP2 and 3.30 mm in HSP3. Morphological abnormalities occurred in 12.5%, 5.0%, and 2.5% of HSP1, HSP2, and HSP3 embryos or larvae, respectively, and predominantly involved axial or vertebral alterations, spinal curvature, and failure to hatch. Conclusion: Acute heat exposure was associated with impaired zebrafish development. Lycopene supplementation was associated with numerically greater body length and a lower descriptive frequency of morphological abnormalities under heat stress conditions, supporting its potential mitigating effect on heat associated developmental impairment.]]>
