Effect of triiodothyronine (T₃) in the larval development of the barber gobyElacatinus figaro

Abstract

The barber goby Elacatinus figaro is an endangered fish, endemic to Brazil and very important to the aquarium trade. One of the bottlenecks for its production in captivity is the larviculture, which is characterized by high mortality rates, especially in the first week after hatching, and prior to metamorphosis. The experiment evaluated the effect of triiodothyronine hormone (T 3 ) on survival, growth and metamorphosis of barber goby. Larvae of 14 days after hatching (DAH) were immersed in three concentrations of T 3 , in triplicate: TC (control) -0; T01 -0.01; T025 -0.025 and T05 -0.05 mg/L. An additional replicate of each treatment was performed for sampling for the histological analysis of the thyroid follicles in 24 DAH larvae. The survival rates in TC, T01, T025 and T05 were 24%, 54%, 36% and 37% respectively, without significant differences between the treatments (p > 0.05). Regarding larval growth, the highest length values were obtained in TC. In T025 and T05, larval metamorphosis was anticipated in up to 11 days in relation to TC and T01. In T01 larvae, follicles were numerous with the presence of reabsorption vesicles in the colloid periphery, indicating increased production of thyroid hormones (THs), associated with the larval metamorphosis process. In T05, a follicle reduction in number and size was observed, given evidence of the end of metamorphosis. The use of 0.025 and 0.05 mg/L of T 3 anticipated metamorphosis in barber goby larvae, shortening the larviculture period for this species.