Effects of chronic ammonia exposure on growth and non-specific immune responses of juvenile soft-shelled turtle Pelodiscus sinensis

Soft-shelled turtles are often exposed to high ambient ammonia levels in intensive rearing conditions.This work evaluated the effects of chronic ammonia exposure on growth and nonspecific immune parameters in juvenile soft-shelled turtles Pelodiscus sinensi.Turtles(body weight:90.5±20.5 g)were subjected to three ammonia concentrations,1.5 mg/L(C1),2.6 mg/L(C2)and 4.1 mg/L(C3)unionized ammonia nitrogen(UIA-N)for 84 days.A control group(C0)was also set up,in which the animals were reared in tap water with no extrinsic NH4Cl.Consistent ambient temperatures(29.5±0.5℃)and pH(7.8±0.1)in each treatment were maintained throughout the experiment.Body weight was measured at 21,42 and 84 days after initiation of ammonia exposure.Blood was sampled on day 84 after initiation of ammonia exposure.In the present concentration range,ammonia showed no clear influence on the turtle's growth.Also,ammonia had no significant effects on non-specific immune parameters such as serum hemolytic activity,bactericidal activity,bacteriolytic activity and the spleen index.However,the non-specific α-naphathyl acetate esterase(ANAE)positive ratios of the blood and spleen lymphocytes both declined in the ammonia treatment groups in relation to the control.The present results indicate that the turtle is fairly resistant to ammonia and may be able to endure much higher ambient ammonia levels than fish.