Sex steroid changes during temperature-induced gonadal differentiation in Paralichthys olivaceus (Temminck & Schegel, 1846)

Abstract

Summary Sex steroid changes during temperature‐induced gonadal differentiation were evaluated in the olive flounder, Paralichthys olivaceus. Larvae were reared at 21 ± 0.5°C, 24 ± 0.5°C and 28 ± 0.5°C from day 40 post‐hatching (dph) to 90 dph. The proportion of males was 61.1, 76.7, 87.8 and 47.8% in 21°C, 24°C, 28°C and in control groups, respectively. Gonadal differentiation was circa 65 dph, when fishes were a mean 39 mm total length (TL). The gonads developed faster when fishes were reared in higher temperatures. Radioimmunoassay (RIA) analyses indicated that the level of estradiol‐17β (E2) changed during the period of gonadal differentiation and peaked at an onset of ovarian differentiation in all groups. Compared with fish in control groups, the levels of E2 were lower in thermal‐treated groups, especially in the highest temperature groups. The present results indicate that E2 plays a major role in the process of ovarian differentiation, and suggest that temperature‐induced masculinization in P. olivaceus is mainly due to a decrease in the E2 level during the period of ovarian differentiation.

Sex-ratio, early sex steroid profiles and cyp19a1b, dmrt1 and foxl2 gene expressions upon high temperature treatment of undifferentiated African catfish juveniles (Clarias gariepinus)

“…Although HT treatment induced a significant masculinization in all tested progenies (masculinization rates ranging from 30 to 100%), we did not observe any differences in T, E2 or 11KT levels during the thermosensitive period; suggesting that high temperature may not act directly on sex steroid production to induce masculinization in African catfish. In the Japanese flounder, HT also did not also affect whole body T levels during gonadal differentiation (Sun et al, 2013), however, E2 levels were significantly reduced during this period (Fan et al, 2017;Sun et al, 2013). In Nile tilapia (D'Cotta et al, 2001a) and European sea bass (Socorro et al, 2007), it was suggested that 11KT concentrations were not influenced by HT treatment as the expression of cyp11b, the gene coding for 11β-hydroxylase, was not influenced during HT treatment.…”

Gonadal Transcriptome Analysis of Male and Female Olive Flounder (Paralichthys olivaceus)

“…Based on our previous study, both testosterone and estradiol-17 β (E2) levels are on rise from ovarian developmental stage I to stage IV. The decrease of E2 level is detected in temperature-induced masculinized groups compared to control groups [ 56 ]. During testicular developmental stage, E2 in the serum stay in low level while T level varies significantly during different developmental stage.…”

Characteristics of Cyp11a during Gonad Differentiation of the Olive Flounder Paralichthys olivaceus

“…The flounder sex has been proved to be determined by genotype, while environmental factors could also alter the gender [ 20 ]. Our previous study showed that 17β-estradiol (E2) in juvenile flounder plays a major role in the process of ovary differentiation, and temperature-induced masculinization was suggested to be mainly due to a decrease of E2 concentration during this process [ 21 , 22 ]. As mentioned above, the sex hormone synthesis-related gene, cyp11a , may be indispensable to gonad differentiation and development in the flounder.…”