Lethal Concentration of Nitrite on Penaeus Chinensis Larvae

Abstract

Penaeus chinensis larvae at the nauplius stage are the most susceptible, while postlarvae are the most tolerant to nitrite. The 24 hr LC50s were 23.12, 56.34, 73.61, and 67.71 mg/l nitrite-N for nauplius third substage (N3), zoea second substage (Z2), mysis second substage (M2), and postlarva twelfth substage (PL12), respectively in 30 ppt seawater at pH 8.21 ± 0.03. The ”threshold time” was found to be 108 hr for PL12 on a toxicity curve approaching an asymptote. Based on the ”incipient LC50” and an application factor of 0.1, the ”safe level” for rearing P. chinensis larvae is estimated to be 1.38 mg/l nitrite-N.將不同時期之中國對蝦蝦苗以靜止換水（Static renewal）方式暴露於一連串亞硝酸一氮溶液中。在所有測試之蝦苗中以無節幼蟲對亞硝酸最敏感，而以後期幼蟲之抵抗力最強。對於N3（無節幼蟲第3期）、Z2（眼幼蟲第2期）、M2（糠蝦蟲第2期）、PL12（後期幼蟲第12期）之24小時LC50分別為23.12、56.34、73.61及67.71毫克／升（鹽度30ppt、pH 8.21 ± 0.03）。對於Z2、M2及PL12之48小時LC50勞別為29.89、25.54及52.14毫克／升。亞硝酸對於PL12之「閾值」在108小時，對於PL12之“incipient LC50”為13.83毫克／升亞硝酸一氮，在繁殖培育中國對蝦蝦苗，亞硝酸－氮之安全基準為1.38毫克／升。