Residues of enrofloxacin, furazolidone and their metabolites in Nile tilapia (Oreochromis niloticus)

The residues of enrofloxacin and its metabolite in Nile tilapia (Oreochromis niloticus) were studied after oral dose of 50 mg/kg for 7 days. To find the differences between Nile tilapia and Chinese shrimp (Penaeus chinensis), the residues of enrofloxacin in P chinensis were also studied under the same conditions. The results showed that enrofloxacin metabolized into ciprofloxacin in both Nile tilapia and P chinensis, the maximal concentration of enrofloxacin in muscle, liver and plasma of Nile tilapia were 3.61 mu g/g, 5.96 mu g/g, 1.25 mu g/ml respectively, and ciprofloxacin in muscle was 0.22 mu g/g. The maximal concentration of enrofloxacin and ciprofloxacin in P chinensis were 1.68 mu g/g and 0.07 mu g/g respectively. The predicted withdrawal time for Nile tilapia was 22 days, and P. chinensis was 12 days under our experiment conditions. The residues of fitrazolidone [3-(5-nitrofurfurylidenamino)-2-oxazolidinone] and its main metabolite 3-amina-2-oxazolidinone (AOZ) in Nile tilapia were first determined by HPLC/MS. Results showed that after oral dose of 30 mg/kg for 7 days, the maximum concentration of farazolidone in Nile tilapia was 413 mu g/kg after 6 h, whereas AOZ residue reached its maximum (31 mu g/kg) right after stopping treatment. In contrast to the high metabolic rate of furazolidone, AOZ was very difficult to eliminate in vivo, thus the withdrawal time of furazolidone in Nile tilapia was 22 days at least. (c) 2005 Elsevier B.V. All rights reserved.

黑颈鹤（Grus nigricollus）种群生态及濒危等级评估

黑颈鹤的种群总量有5000～6000 只个体,主要分布在青藏高原和云贵高原,分布区约22 ×105km2 ,占有面积约5400 km2 。青藏高原北部和西部为其繁殖区,越冬区主要在雅鲁藏布江河谷中段、喜马拉雅山脉南坡及云贵高原部分区域,青藏高原东部为其迁徙途径之地。越冬时以家族、同种群及混合群(主要与灰鹤Grus grus 和斑头雁A nser indicus) 形式集群活动。繁殖期分化为非繁殖群和繁殖对(Breeding pair) 两种类型。繁殖对能否成功地占有领域是繁殖成败的关键。笔者认为该物种依IUCN(1994) 标准应列为易危级(Vulnerable ,VU)