Jagadeesan L, Jyothibabu R
CSIR - National Institute of Oceanography, Regional Centre, Kochi, 682018, India.
Environ Monit Assess. 2016 Apr;188(4):244. doi: 10.1007/s10661-016-5230-6. Epub 2016 Mar 24.
Globally, tumour-like anomalies (TLA) in copepods and the critical assessment of their possible causes are rare. The exact causative factor and ecological consequences of TLA in copepods are still unclear and there is no quantitative data available so far to prove conclusively the mechanism involved in developing TLA in copepods. TLA in copepods are considered as a potential threat to the well-being of the aquatic food web, which prompted us to assess these abnormalities in Indian marine waters and assess the possible etiological agents. We carried out a focused study on copepods collected from 10 estuarine inlets and five coastal waters of India using a FlowCAM, advanced microscopes and laboratory-incubated observations. The analysis confirmed the presence of TLA in copepods with varying percentage of incidence in different environments. TLA was recorded in 24 species of copepods, which constituted ~1-15 % of the community in different environments. TLA was encountered more frequently in dominant copepods and exhibited diverse morphology; ~60 % was round, dark and granular, whereas ~20 % was round/oval, transparent and non-granular. TLA was mostly found in the dorsal and lateral regions of the prosome of copepods. The three suggested reasons/assumptions about the causes of TLA such as ecto-parasitism (Ellobiopsis infection), endo-parasitism (Blastodinium infection) and epibiont infections (Zoothamnium and Acineta) were assessed in the present study. We did find infections of endo-parasite Blastodinium, ecto-parasite Ellobiopsis and epibiont Zoothamnium and Acineta in copepods, but these infectious percentages were found <1.5 % to the total density and most of them are species specific. Detailed microscopical observations of the samples collected and the results of the incubation experiments of infected copepods revealed that ecto-parasitism, endo-parasitism and epibiont infections have less relevance to the formation of TLA in copepods. On the other hand, these studies corroborated the view that wounds on the exoskeleton caused by partial predation as the potential reason for the TLA of copepods in Indian waters.
在全球范围内，桡足类动物中的肿瘤样异常（TLA）以及对其可能成因的批判性评估都很罕见。桡足类动物中TLA的确切致病因素和生态后果仍不清楚，目前尚无定量数据能够确凿证明桡足类动物发生TLA的机制。桡足类动物中的TLA被认为是对水生食物网健康的潜在威胁，这促使我们评估印度海域的这些异常情况，并评估可能的病原体。我们使用流式细胞仪、先进显微镜以及实验室培养观察法，对从印度10个河口湾入口和5个沿海水域采集的桡足类动物进行了重点研究。分析证实桡足类动物中存在TLA，在不同环境中的发生率各不相同。在24种桡足类动物中记录到了TLA，在不同环境中其占群落的比例约为1%-15%。TLA在优势桡足类动物中更频繁出现，且形态多样；约60%为圆形、深色且有颗粒状，约20%为圆形/椭圆形、透明且无颗粒状。TLA大多出现在桡足类动物前体的背部和侧面区域。本研究评估了关于TLA成因的三种推测原因/假设，即体外寄生（艾氏寄生虫感染）、体内寄生（布拉氏藻感染）和附着生物感染（聚缩虫和艾氏虫）。我们确实在桡足类动物中发现了体内寄生虫布拉氏藻、体外寄生虫艾氏寄生虫以及附着生物聚缩虫和艾氏虫的感染，但这些感染占总密度的比例不到1.5%，且大多具有物种特异性。对采集样本的详细显微镜观察以及受感染桡足类动物的培养实验结果表明，体外寄生、体内寄生和附着生物感染与桡足类动物中TLA的形成关联较小。另一方面，这些研究证实了这样一种观点，即部分捕食导致的外骨骼伤口是印度海域桡足类动物出现TLA的潜在原因。
