Hormonal and physiological changes in Sterlet sturgeon Acipenser ruthenus treated with thyroxine

Abstract

This study investigates the basis of the stimulatory effects of thyroxine (T4) on the growth and physiological changes in Sterlet sturgeon broodstock and their larval offspring. Groups of fish received four injections of 0, 1 or 10 mg kg BW−1 of T4 over a 170-day period. At the end of trial, blood was taken and plasma biochemical parameters, sex steroid and thyroid hormone (THs) levels were measured. Broodstock were induced to ovulate by the injection of LHRHa2 and ovarian fluid (OF) and eggs were obtained through a minimally invasive surgical technique. The eggs were fertilized and resulting larvae were assessed after 14 days of grow out. Weight gain, protein and lipid efficiency and food efficiency of broodstock in T10 were higher than the other treatments (P < 0.05). The cholesterol, triglyceride, total protein, albumin and glucose levels in OF were higher in the T10 group than the other groups (P < 0.05). Similarly, calcium, magnesium and phosphorus concentrations in the OF of the T10 group were higher than the other treatments. Furthermore, plasma cholesterol, triglyceride, HDL, VLDL and calcium levels were significantly enhanced in the T10 group compared to the other groups, while, plasma phosphorus and magnesium were not significantly affected. Additionally, the T10 group displayed lowest LDL plasma levels (P < 0.05). The highest and lowest concentrations of testosterone and 17β-estradiol were recorded in T10 group. Moreover, the highest levels of TH were found in T10, while, control group had the lowest TH concentrations. The offspring from the T10 treatment had the lowest mortality rate at 3 dph. This study highlights that 10 mg T4 kg BW−1 promoted biochemical and metabolic changes in the adult Sterlet broodstock that were associated with enhanced egg fertility and larval survivability.