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High lead exposure and clinical signs of toxicosis in wild Nile crocodiles (Crocodylus niloticus) from a World Heritage site: Lake St Lucia estuarine system, South Africa
Chemosphere ( IF 8.1 ) Pub Date : 2022-05-17 , DOI: 10.1016/j.chemosphere.2022.134977
Marc Humphries 1 , Jan Myburgh 2 , Robert Campbell 3 , Xander Combrink 4
Affiliation  

Lead (Pb) exposure is a widespread wildlife conservation threat, but impacts on reptile populations remain poorly documented. In this study, we examined Pb exposure and accumulation in a wild population of Nile crocodiles (Crocodylus niloticus) at Lake St Lucia, South Africa. Recreational angling has occurred in the area since the 1930s and incidental ingestion of Pb fishing weights has previously been identified as a major source of Pb poisoning in the local crocodile population. In 2019, we sampled blood and tail fat tissues from wild (n = 22) and captive (n = 3) crocodiles at Lake St Lucia to investigate potential impacts of chronic Pb exposure on crocodilian health. Lead was detected in blood samples of all wild crocodiles, although concentrations varied widely between individuals (86–13,100 ng ml−1). The incidence of Pb poisoning was higher in male crocodiles, with mean blood lead (BPb) concentrations in males (3780 ± 4690 ng ml−1) significantly (p < 0.001) higher compared to females (266 ± 230 ng ml−1). Blood Pb concentrations were correlated with concentrations measured in tail fat tissue (n.d – 4175 ng g−1 wet wt.). Although most of the crocodiles sampled appeared to be in good physical condition, highly elevated BPb concentrations (>6000 ng ml−1) were associated with markedly suppressed packed cell volumes (4.6–10.8%) and severe deterioration in tooth condition. These findings suggest that anaemia and tooth loss may be clinical signs of long-term environmental exposure to Pb. Although previously undocumented in crocodilians, these symptoms are consistent with Pb poisoning observed in birds and mammals, and suggest that crocodilians may be more susceptible to the long-term toxic effects of Pb than previously thought. In light of these findings, we suggest that the impact of accumulated Pb on crocodilian fitness, reproduction and mortality requires urgent attention.

中文翻译:


世界遗产地野生尼罗河鳄鱼 (Crocodylus niloticus) 的高铅暴露量和中毒临床体征:南非圣卢西亚湖河口系统



铅 (Pb) 暴露是一种广泛的野生动物保护威胁,但对爬行动物种群的影响仍然记录不足。在这项研究中,我们检查了南非圣卢西亚湖尼罗河鳄鱼 (Crocodylus niloticus) 野生种群的铅暴露和积累。自 1930 年代以来,该地区一直存在休闲垂钓活动,偶然摄入 Pb 钓鱼重物此前已被确定为当地鳄鱼种群 Pb 中毒的主要来源。2019 年,我们在圣卢西亚湖采集了野生 (n = 22) 和圈养 (n = 3) 鳄鱼的血液和尾部脂肪组织样本,以研究长期接触铅对鳄鱼健康的潜在影响。在所有野生鳄鱼的血液样本中检测到铅,尽管个体之间的浓度差异很大 (86-13,100 ng ml-1)。雄性鳄鱼的铅中毒发生率较高,雄性 (3780 ± 4690 ng ml-1) 的平均血铅 (BPb) 浓度显著高于雌性 (266 ± 230 ng ml-1)。血液 Pb 浓度与在尾部脂肪组织中测量的浓度相关 (n.d – 4175 ng g-1 wet wt.)。尽管大多数取样的鳄鱼似乎身体状况良好,但高度升高的 BPb 浓度 (>6000 ng ml-1) 与显着抑制的压积细胞体积 (4.6-10.8%) 和牙齿状况的严重恶化有关。这些发现表明,贫血和牙齿脱落可能是长期环境暴露于 Pb 的临床体征。虽然以前在鳄鱼中没有记录,但这些症状与在鸟类和哺乳动物中观察到的 Pb 中毒一致,并表明鳄鱼可能比以前认为的更容易受到 Pb 的长期毒性作用。 鉴于这些发现,我们建议需要紧急关注积累的 Pb 对鳄鱼适应性、繁殖和死亡率的影响。
更新日期:2022-05-17
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