This paper reports an evaluation of growth, gonadal development and reproductive endocrinology of older triploid (3n) sea bass Dicentrarchus labrax in comparison to their diploid (2n) counterparts throughout their 5th and 7th annual cycle of life. While older triploids retained impaired reproductive endocrinology, a sexually-related dimorphic growth was observed with 3n females attaining the largest sizes. Comparisons of some body indexes showed that 3n females had a significantly lower hepato-somatic index (IH) than 2n females but a significantly higher viscero-somatic index (IF). In contrast, both male and female triploids showed significantly lower gonado-somatic index (IG) than diploids. Accordingly, diploids produced mature gametes but triploids did not, demonstrating that despite the longer time given to triploids for gonadal development, they could not reproduce. Furthermore, older triploids had lower levels of plasma sex steroids (testosterone, T; 11-ketotestosterone, 11-KT and estradiol-17?? E2) and luteinizing hormone (LH) than their 2n counterparts with 3n females showing drastic effects of triploidisation on their reproductive endocrinology. Vitellogenin (VTG) was undetectable in 3n females. Gonadal content of steroid hormones and sea bream gonadotropin-releasing hormone (sbGnRH) in the brain and pituitary were also lower in triploids compared to diploids. These results suggest that 3n older D. labrax retain functional sterility in both sexes and 3n females might reach larger sizes than 3n males and their 2n counterparts in this species.
