Laboratory of Animal Physiology, Department of Zoology, School of Biology, Faculty of Science, Aristotle University of Thessaloniki, 54124, Thessaloniki, Greece.
Department of Animal Science, Faculty of Agricultural Sciences, University of Western Macedonia, 53100, Florina, Greece.
Mar Environ Res. 2020 Mar;155:104889. doi: 10.1016/j.marenvres.2020.104889. Epub 2020 Jan 23.
Mycobacterium sp. and Haplosporidium pinnae constitute invasive parasite species of bivalves, reported for the first time in the present study in the Aegean Sea and Thermaikos Gulf, respectively. During the last years, the endangered fan mussel (Pinna nobilis) experienced several mortality events in the Mediterranean Sea that caused deaths to 90% or more of their populations and have been attributed to infections by these pathogens. In Greece, two mass mortality events have been recently reported, namely in the Gulf of Kalloni and in Limnos island. In the present study we investigated the presence of both pathogens in P. nobilis from these marine areas as well as from Thermaikos Gulf using both histopathological microscopy and molecular markers. The detected parasite DNA was further quantified in the three populations utilizing a real time qPCR. Histopathological results indicated the presence of a Mycobacterium species alongside with the existence of the Haplosporidian parasite, which was identified in all mortality events in the Mediterranean Sea. The parasite was present in different phases mostly on the digestive gland epithelium. Phylogenetic analysis confirmed the taxonomy of the Haplosporidian parasite as the recently described Haplosporidium pinnae, whereas it failed to identify the Mycobacteria parasite at species level. While Mycobacterium sp. was detected in all examined specimens, H. pinnae was not detected in all diseased fan mussels. Interestingly, monitoring of P. nobilis population from Thermaikos Gulf, an estuary of extremely high importance for bivalve production, revealed the presence of both pathogens in a few specimens in higher quantity but with no symptoms of the disease. Besides, all the specimens from Thermaikos Gulf had inflammatory responses similarly to moribund specimens from mortality events.
分枝杆菌属和 Haplosporidium pinnae 构成了贝类的侵袭性寄生虫物种，分别是本研究首次在爱琴海和 Thermaikos 湾报道的。在过去的几年中，濒危的扇贻贝（Pinna nobilis）在地中海经历了几次死亡率事件，导致其种群的 90%或更多死亡，并归因于这些病原体的感染。在希腊，最近报告了两起大规模死亡事件，分别是在 Kalloni 湾和 Limnos 岛。在本研究中，我们使用组织病理学显微镜和分子标记物调查了来自这些海洋区域以及 Thermaikos 湾的 P. nobilis 中这两种病原体的存在情况。利用实时 qPCR 进一步定量了在这三个种群中检测到的寄生虫 DNA。组织病理学结果表明，存在一种分枝杆菌属物种，同时存在 Haplosporidian 寄生虫，该寄生虫存在于地中海所有的死亡率事件中。寄生虫主要存在于消化腺上皮的不同阶段。系统发育分析证实了 Haplosporidian 寄生虫的分类为最近描述的 Haplosporidium pinnae，而未能在种水平上鉴定分枝杆菌属寄生虫。虽然分枝杆菌属在所有检查的标本中均被检测到，但并非所有患病扇贻贝都未检测到 H. pinnae。有趣的是，对 Thermaikos 湾（对双壳类生产极为重要的河口）的 P. nobilis 种群进行监测时，发现了一些标本中存在两种病原体，且数量较高，但没有疾病症状。此外，Thermaikos 湾的所有标本都与死亡率事件中的濒死标本具有相似的炎症反应。
