Lumme Jaakko, Zietara Marek S
Department of Ecology and Genetics, University of Oulu, Finland.
Faculty of Biology, University of Gdansk, Poland This article contains supporting information (S1-S4) online at http://folia.paru.cas.cz/suppl/2018-65-006.pdf.
Folia Parasitol (Praha). 2018 Apr 19;65:2018.006. doi: 10.14411/fp.2018.006.
In the parthenogenetic monogeneans of the genus Gyrodactylus Nordmann, 1832, the genetic diversity within or between hosts is determined by the relative roles of lateral transmission and clonal propagation. Clonality and limited transmission lead to high-amplitude metapopulation dynamics and strong genetic drift. In Baltic populations of the three-spined stickleback Gasterosteus aculeatus Linnaeus, the local mitochondrial diversity of Gyrodactylus arcuatus Bychowsky, 1933 is very high, and spatial differentiation weak. To understand the transmission dynamics in a single location, the transmission of the parasite from adults to next generation sticklebacks was investigated in a northern Baltic brackish water location. By sequencing 777 nt of cox1, as many as 38 separate mitochondrial haplotypes were identified. In August, the intensity of gyrodactylid infection on adult hosts was high, the haplotype diversity (h) was extreme and differentiation between fish was negligible (total h = 0.926, mean h = 0.938). In October, only 46% of the juvenile sticklebacks carried G. arcuatus. The number of parasites per young fish followed a Poisson distribution 0.92 ± 1.04 (mean ± SD) on October 2, and was clearly overdispersed 2.38 ± 5.00 on October 25. The total haplotype diversity of parasites on juveniles was nearly as high as in adults (h = 0.916), but the mean per fish was only h = 0.364 (F = 0.60), due to low intensity of infection and rapid clonal propagation of early arrivals. The initial first come first served advantage of the first gyrodactylid colonisers will be lost during the host adulthood via continuous transmission. Nesting and polygamy are suggested as factors maintaining the high genetic diversity of the parasite population. The transmission dynamics and, consequently, the population structure of Baltic G. arcuatus is fundamentally different from that of G. salaris Malmberg, 1957, on the Baltic salmon Salmo salar Linnaeus.
在1832年命名的三代虫属（Gyrodactylus Nordmann）孤雌生殖的单殖吸虫中，宿主内部或宿主之间的遗传多样性由横向传播和克隆繁殖的相对作用决定。克隆性和有限的传播导致高振幅集合种群动态和强烈的遗传漂变。在波罗的海三刺鱼（Gasterosteus aculeatus Linnaeus）的种群中，1933年命名的弓形三代虫（Gyrodactylus arcuatus Bychowsky）的局部线粒体多样性非常高，空间分化较弱。为了了解单个地点的传播动态，在波罗的海北部咸淡水区域对该寄生虫从成年三刺鱼向新一代三刺鱼的传播进行了调查。通过对细胞色素氧化酶亚基1（cox1）的777个核苷酸进行测序，共鉴定出多达38种不同的线粒体单倍型。8月，成年宿主上三代虫感染强度很高，单倍型多样性（h）极高，鱼之间的分化可忽略不计（总h = 0.926，平均h = 0.938）。10月，只有46%的幼年三刺鱼携带弓形三代虫。10月2日，每条幼鱼身上的寄生虫数量呈泊松分布，为0.92 ± 1.04（平均值 ± 标准差），而在10月25日明显呈过度分散分布，为2.38 ± 5.00。幼鱼身上寄生虫的总单倍型多样性几乎与成鱼一样高（h = 0.916），但由于感染强度低和早期到达者的快速克隆繁殖，每条鱼的平均单倍型多样性仅为h = 0.364（F = 0.60）。第一代三代虫定居者最初的先来先得优势在宿主成年期通过持续传播会丧失。筑巢和多配偶制被认为是维持寄生虫种群高遗传多样性的因素。波罗的海弓形三代虫的传播动态以及因此产生的种群结构与1957年命名的寄生于波罗的海鲑鱼（Salmo salar Linnaeus）上的鲑三代虫（G. salaris Malmberg）根本不同。
