Larval performance of matrinxã, Brycon amazonicus (Spix & Agassiz 1829), after maternal triiodothyronine injection or egg immersion

This study compared the larval performance of matrinxã, Brycon amazonicus, after maternal triiodothyronine (T₃) injection or egg immersion of T₃. In the first experiment, three groups of females (n=4) induced to spawning received pituitary extract (CPE) and a corn oil injection (control), or CPE plus 10 mg or 20 mg kg^?1 bw T₃ dissolved in corn oil (experimental). Larvae were sampled for body weight and length measurement at hatching (0 h) and 12, 24, 36, 48 and 60 h thereafter. Hatching time, hatching success and abnormal development were monitored. In the second experiment, fertilized eggs from four females were immersed in T₃ solutions (0, 0.01, 0.05 and 0.10 mg L^?1) and larvae were sampled at hatching (0 h) and 6, 18, 30, 42, 54, 126 and 198 h thereafter. Hatching time was not affected by either means of hormone treatment. Abnormalities decreased as the T₃ concentration increased in larvae from T₃‐treated broodfish but the number of dead larvae increased proportionally. Larvae from T₃‐injected females had higher weight from 24 h after hatching and greater length from hatching, while the weight of larvae produced from T₃‐immersed eggs changed at 198 h and length from 126 h of rearing. Both routes of T₃ administration affected the early growth of matrinxã but the effect was observed earlier when broodstock females were injected.