Abstract

The palm ruff (Seriolella violacea) is a marine fish species of high relevance to fisheries along the Pacific coast of South America, and in the last decade with great potential for aquaculture diversification in the South Pacific. This fish typically inhabits environments with temperatures ranging from 13 degrees C to 18 degrees C. However, the optimal temperature for its growth in the early stages of development is still unknown. This study assessed the effects of a temperature gradient on survival, oxygen consumption, oxidative stress, and tissue morphology in S. violacea larvae at 50-55 days post-hatching (dph). Mortality significantly increased above 21 degrees C, indicating greater sensitivity to elevated rather than reduced thermal conditions. Oxygen consumption significantly decreased at both low (5-7 degrees C) and high (23-25 degrees C) temperatures. Superoxide dismutase (SOD) activity rose above 11 degrees C, while oxidative stress biomarkers showed peak protein carbonylation at 7 degrees C and maximal lipid peroxidation at 25 degrees C. Enhanced expression of the HSP70 chaperone, as evaluated via immunohistochemistry, was noted in erythrocytes and mucosal tissue of fish kept at temperatures below 7 degrees C and above 23 degrees C. In addition, morphological alterations were most evident in skin and gills of fish maintained at temperatures outside the 7-21 degrees C range, including vascular changes and elevated goblet cell numbers. Overall, the results suggest that S. violacea employs compensatory responses to withstand acute thermal stress, including metabolic adjustments, enhanced mucus secretion, and increased blood flow. This study provides valuable insights into the thermal tolerance and physiological plasticity of S. violacea during larval culture. However, acute episodes of extreme temperatures can trigger oxidative damage and tissue dysfunction, ultimately decreasing larval survival.