Abstract:Acute toxicity of ten chemicals to sea squirt Ciona intestinalis was tested. Seven of the ten drugs showed no lethal effect on C. intestinalis. These drugs were zinc sulfate (≤3 mg/L), sodium bicarbonate (≤2.5%), tea saponin (≤6.7 ml/L), cypermethrin (≤0.2 ml/L), trichlorfon refined flour (≤4 mg/L), trichlorfon and phoxim mixture (≤3 mg/L) and potassium permanganate (≤5 mg/L).In contrast, copper sulfate (≥1 mg/L), MQL (≥5 mg/L) and garlicin mixture (MQS)(≥15 mg/L) could kill sea squirt in 24 h, and the half lethal concentrations (LC50) of these three chemicals were 0.58 mg/L,3.33 mg/L and 10.80 mg/L, respectively. At the concentration of 1 mg/L, copper sulfate could induce juvenile Apostichopus japonicus to disgorge their intestines in 3 h. Thus, copper sulfate is not suitable for use in culture practice. In addition, MQL and MQS had no toxin effects to juvenile A. japonicus in 96 h at the concentration of 10 mg/L and 20 mg/L, respectively. Therefore, MQL and MQS were considered as the effective drugs to kill C. intestinalis in the sea cucumber nursery system, and the dosage of 5 mg/L and 15 mg/L for soaking 24 h were recommended in their application. This method is effective to kill C. intestinalis in sea cucumber hatchery.
