Dose-dependent Effects of Thyroxine (T4) Immersion on Growth and Survival of Giant Gourami (Osphronemus goramy) Fry

Abstract

The immersion gourami larvae and fry in a thyroxine hormone solution requires an optimal dosage suitable for larval or fry growth and survival. Excessive doses of T4 accelerate the larvae's metabolism and damage the nervous system, liver, and heart, leading to larval mortality. Although gourami fish is a significant economic commodity in Indonesia, slow fish growth and fry mortality rates hinder fingerlings production. The objective of this study was to determine the optimal thyroxine hormone dosage to promote Osphronemus goramy fry growth and survival (10 days after hatching). Six thyroxine dosage treatments (A: 0.00 mg/L; B: 0.25 mg/L; C: 0.5 mg/L; D: 0.75 mg/L; E: 1.00 mg/L; and F: 1.25 mg/L) and four replications were used in this completely randomized design. The gourami fry's weight, length, and survival over the course of 60 days of maintenance are test parameters. The results of the analysis of variance test revealed that immersion gourami fry with thyroxine considerably improved their growth and survival when compared to non-immersed fry. The Duncan's Multiple Range test showed that a thyroxine hormone dosage of 1.00 mg/L produced an optimal survival rate of 91% and growth body length and weight of 8.04 cm and 9.2 g. The results of this study indicate that growth hormone receptor gene expression is present in the target tissues of the thyroxine hormone. This indication can be seen in each thyroxine dose treatment resulting in increased fry weight compared to without thyroxine.