عنوان مقاله [English]
A completely randomized design was conducted to determine the effect of four concentrations of waterborne sodium (2, 14, 50, 100 mg L-1) on excretion of ammonia in embryonic rainbow trout in a water recirculating system. Twelve experimental units, with the capacity of holding 45 liter of water were used and 22.5 g egg introduced in each one. Different water media (treatments) was made using analytical salts (Merck) added into double-de-ionized distilled water. Water temperature variations during incubation period were 7.5-9 ºC. Ammonia in external water measured during the incubation period every week. Prior to allocating the newly fertilized eggs to trays as well as at the time of hatching, sodium ion and total nitrogen measured in the whole egg. Ammonia level was significantly (P<0.05) different in treatments, so that the highest ammonia level was observed in the [Na+] 2 mg L-1. In all treatments, total nitrogen of the whole egg did not significantly (P>0.05) change compared to newly fertilized one. In the variation of the whole egg Na+ was significant (P<0.05) among treatments and the newly fertilized egg. The whole egg sodium content in [Na+] 100 mg L-1 was higher than the other treatments. The results of this study indicated that excretion of ammonia by embryos of rainbow trout to external water does not increase along with increasing waterborne sodium concentration and higher sodium uptake by egg.