Effects of thyroxine immersion on Sterlet sturgeon (Acipenser ruthenus) embryos and larvae: Variations in thyroid hormone levels during development

Abstract

This study was planned to investigate the effects of immersion of Sterlet sturgeon (Acipenser ruthenus) eggs by thyroxine hormone (T4) on the embryonic survival rate (ESR), hatching rate (HR), larval survival rate (LSR), and thyroid hormone levels. Hence, oocytes of six females were pooled, fertilized with pooled semen of three males and 45 min after fertilization process, the eggs were placed 120 min in four batches that were immersed in T4 solutions as follows: D1 (the control treatment: T4-free, hatchery water), D2 (0.01 mg L−1 of T4), D3 (0.05 mg L−1 of T4), D4 (0.1 mg L−1 of T4), and D5 (1 mg L−1 of T4). Next, the eggs were transferred to the incubator. The ESR was recorded 6 h after fertilization while HR, and LSR were measured at 1 day post hatching. In addition, the levels of thyroid hormones were measured using the competitive enzyme immunoassay method three hours and three days after fertilization and at the five-day pre-larval stage. The highest ESR was obtained following D5 treatment (P < .05). Besides, the highest and lowest HR were observed in D5 and D1 treatments, respectively (P < .05). The D5 treatment resulted in the highest pre-larval SR. During all sampling times, the D5 treatment resulted in the highest level of thyroid hormones among the other treatments (P < .05). However, the T3:T4 ratio was significant only within the three days after fertilization in D1 treatment (P < .05). In general, it can be concluded that the immersion of Sterlet sturgeon eggs in T4 improved the ESR, hatching, and LSR of this species, resulting in a promising future for the aquaculture of Sterlet sturgeon and other sturgeon species.