Comparison of LC-PUFAs Biosynthetic Characteristics in Male and Female Tilapia at Different Ontogenetic Stages.

Tilapia possess the ability to biosynthesize long-chain polyunsaturated fatty acids (LC-PUFA); however, variations in this capacity across different growth stages and between sexes remain poorly understood. This study evaluated the LC-PUFA biosynthetic capacity in male and female tilapia fed two distinct diets-perilla oil (rich in α-linolenic acid, ALA) and peanut oil (rich in linoleic acid, LA)-over 24 weeks, spanning four growth stages (I-IV, from fry to adult). The results revealed that during stages I to III, both diets produced similar final body weights. However, in stage IV, male tilapia fed the peanut oil diet exhibited significantly higher body weight compared to those fed perilla oil, whereas females showed no significant differences between diets. Throughout stages III and IV, males were consistently heavier than females. LC-PUFA levels in the liver and intestine varied across growth stages, with the lowest levels at stage II and the highest at stage III. Notably, male tilapia exhibited higher expression levels of fads2 and elovl5 compared to the females across stages II to IV. The hepatic and intestinal mRNA levels increased by up to 6.40-fold and 3.85-fold, respectively, indicating a greater LC-PUFA biosynthetic capacity in males. This study provides valuable insights into the biosynthesis of LC-PUFA in tilapia, highlighting the influence of growth stage, sex and dietary fatty acid composition on this process, and laying a foundation for further evaluating the functional significance of dietary lipid sources in aquaculture.