海水和饲料中Pb在凡纳滨对虾体内的富集与释放特性

为获知海水和饲料中重金属Pb与凡纳滨对虾(Litopenaeus vannamei)各组织间的富集与释放特性,应用生物富集双箱动力学模型,模拟凡纳滨对虾分别在海水中Pb浓度为0.0015 mg/L(B0)、0.0080 mg/L(B1)、0.0466 mg/L(B2)和0.2302 mg/L(B3),饲料中Pb浓度为2.089 mg/kg(A0)、2.750 mg/kg(A1)、6.103 mg/kg(A2)和14.520 mg/kg(A3)的驯养过程中,其肝胰腺、外骨骼和肌肉对Pb的生物富集与释放特性,为Pb在凡纳滨对虾体内的分布、富集和迁移提供理论依据,为其安全生产提供指导意义。同时通过非线性拟合得到凡纳滨对虾对海水和饲料中Pb的富集速率常数K1、排出速率常数K2、生物富集系数BCF、生物半衰期B_(1/2),富集平衡时生物体内Pb含量CAmax等动力学参数。结果显示:(1)投喂任一浓度饲料时,B0、B1、B2组凡纳滨对虾肌肉、外骨骼和肝胰腺组织中Pb含量均小于限量值0.5 mg/kg,而在B3海水浓度中,随着投喂饲料浓度的增大,各组织中Pb累积量高于限量值(0.5 mg/kg)的时间出现得越来越早;肝胰腺中Pb的释放速率高于肌肉和外骨骼的释放速率。(2)用SPSS18.0对饲料Pb含量、海水浓度、富集时间进行三因素重复测量方差分析显示,饲料浓度、海水浓度和富集时间对凡纳滨对虾各组织中Pb的富集含量出现显著性差异除了饲料浓度对凡纳滨对虾外骨骼组织中Pb富集主效应达到边缘显著(F=2.351,P=0.071)],且饲料、海水及时间交互效应分析显示,三者交互作用显著。(3)用SPSS18.0对不同组织中Pb的富集含量、饲料浓度、海水浓度和富集时间进行多元回归分析,结果显示:在凡纳滨对虾各组织间Pb富集过程中,海水中Pb浓度的贡献率大于饲料中Pb浓度的贡献率。(4)达到平衡状态下,投喂A0饲料浓度,生长在B0~B3组海水中,凡纳滨对虾肌肉组织中Pb含量为0.128~2.981 mg/kg,肝胰腺组织中Pb含量为0.399~4.765 mg/kg;生物学半衰期(B_(1/2))范围分别为5~7 d和3~7 d。投喂A2饲料浓度,生长在B0~B3组海水中,凡纳滨对虾肌肉组织中Pb含量为0.380~1.000 mg/kg,肝胰腺组织中Pb含量为0.288~5.355 mg/kg;生物学半衰期(B_(1/2))范围分别为2~7 d和2~5 d。理论平衡浓度下,肝胰腺组织中含量均大于肌肉。

Lead enrichment and release characteristics in seawater and Litopenaeus vannamei feed

Kinetic parameters were determined for the biological accumulation and release of lead (Pb) in muscle, the hepatopancreas, and exoskeleton of Litopenaeus vannamei to assess the enrichment and release characteristics of Pb in seawater, feed, and tissues using a two-compartment bioconcentration model. Shrimp were exposed to seawater with Pb concentrations of 0.0015 mg/L(B0), 0.0080 mg/L(B1), 0.0466 mg/L(B2), and 0.2302 mg/L(B3). Shrimp were provided a diet with Pb concentrations of 2.089 mg/kg(A0), 2.750 mg/kg(A1), 6.103 mg/kg(A2), and 14.520 mg/kg(A3). The heavy metal uptake rate constant (k1), extraction rate constant (k2), bioconcentration factor (BCF), biological half-life(B1/2), and the equilibrium concentrations of heavy metalsin vivo(CAmax) were obtained by non-linear curve fitting. The results showed that muscle, exoskeletal, and hepatopancreatic tissue contents were less <0.5 mg/kg after feeding Pb. Pb in all tissues increased to >0.5 mg/kg after exposing shrimp to the two lower Pb concentrations in seawater as the Pb concentration in feed was increased in shrimp in the B3 seawater treatment. The Pb release rate by the hepatopancreas was higher than that by muscle or the exoskeleton. A three factor re-peated-measures analysis of variance with feed concentration, seawater concentration, and enrichment time as the factors showed that all three factors had significant effects in the different tissues. In addition, the Pb accumulating effect in the exoskeleton based on feed concentration was marginally significant (F=2.351,P=0.071). A feed, seawater, and time interaction effect analysis resulted in a significant interaction among the three factors. An analysis of Pb feed and seawater concentrations, as well as Pb duration in different tissues showed that the contri-bution of Pb concentration in seawater was greater than that in feed during Pb enrichment in each tissue. At steady state, the Pb concentrations in muscle of shrimp in the A0 and B0–B3 groups were 0.128–2.981 mg/kg, and those in the hepatopancreas were 0.399–4.765 mg/kg. TheB1/2values for Pb in the muscle and hepatopancreas were 2–7 d and 3–7 d, respectively. The Pb concentrations in muscle of shrimp from the A2 and B0–B3 groups were 0.380–1.000 mg/kg, and in the hepatopancreas were 0.288–5.355 mg/kg. TheB1/2values for Pb in muscle and hepatopancreas were 2–7 d and 2–5 d. The steady state concentration of Pb in the hepatopancreas was higher than that in muscle.