PRELIMINARY STUDY OF THE EFFECT OF MATERNAL TRIIODOTHYRONINE ON EARLY DEVELOPMENT OF MATRINXA BRYCON CEPHALUS (CHARACIDAE)

摘要

The experiment tested the effect of maternally administered triiodothyronine (T_3) on the performance of matrinxa (Brycon cephalus) larvae, an economically important freshwater fish in South America. Progenies from female injected with carp pituitaryextract CPE (control group) and from female injected with CPE plus triiodothyronine (20 mg/kg bw) experimental group) were randomly distributed in 5 replicate aquaria per treatment (10 larvae/L) and sampled at 1, 6, 9, 12 and 18 days of culture, starting72 hours after hatching. Following the larvae stocking in the aquaria they fed zooplankton ad libitum twice a day (09.00 and 16.00 h) during the whole experiment. Additionally, a powder ration (30.9% crude protein) was provided four times a day (09.00,12.00, 16.00 and 21.00 h), 2 g for each aquarium in the three first days and 4 g in the fifteen remaining days. Until day 6 larvae of the experimental group had higher growth than larvae of the control group. At day 9 both groups showed similar growth and at days 12 and 18 the control group showed higher growth compared to the experimental group. Reminders of larvae were found only in the stomachs of control larvae up to 9 days of culture. Control larvae presented a marked heterogeneous growth, lower final biomass (66.5 g and 102.8 g for control and experimental group, respectively) and lower survival (21.8% and 61.6% for control and experimental group, respectively) without observed mortalities. Data were analyzed using one-way ANOVA and Tukey test (P< 0.05). The results suggest that maternal thyroid hormone may have enhanced the performance and survival of matrinxa larvae by reducing cannibalism.