Isaksen T E, Karlsbakk E, Sundnes G A, Nylund A
Department of Biology, University of Bergen, Thormøhlensgaten 55, 5020 Bergen, Norway.
Dis Aquat Organ. 2010 Feb 17;88(3):207-14. doi: 10.3354/dao02173.
Infection patterns with ectoparasitic flagellates belonging to the genus Ichthyobodo were studied in an Atlantic salmon Salmo salar (L.) hatchery in western Norway during an 11 mo period, from eyed eggs to smoltification. Since the earlier species designation Ichthyobodo necator (sensu lato, s.l.) has been shown to represent a complex of several species, the epizootiology of different Ichthyobodo spp. is poorly known. Therefore, we employed molecular methods to ascertain the specific identity of the parasites detected in our study. Only I. necator in the recently redefined and restricted sense occurred (I. necator sensu stricto, s.s.). We observed a 2-peak pattern of infection; the first peak occurred among fry in March and the second peak among fingerlings and pre-smolt in August and September. Skin lesions observed on fingerlings and pre-smolt were significantly associated with Ichthyobodo infections. Also, these infections were negatively correlated with both haematocrit values (Hct) and the condition factor (K) of the fish. The patterns of infection on the farmed salmon suggest that I. necator s.s. is an opportunistic parasite of salmon, flourishing in periods when susceptible hosts are present and the environment favours parasite proliferation. Our study is the first to detect and identify I. necator s.s. on wild-caught adult salmonids (brown trout S. trutta L.). Wild salmonids and sticklebacks Gasterosteus aculeatus (L.) caught in the lakes serving as a water supply to the hatchery were found infected with I. necator s.s., hence these are the likely sources of parasites entering the hatchery via the inlet water.
在挪威西部的一个大西洋鲑鱼（Salmo salar，L.）孵化场，对属于鱼波豆属（Ichthyobodo）的体外寄生鞭毛虫的感染模式进行了为期11个月的研究，研究对象从有眼卵到幼鲑化阶段。由于早期的物种命名鱼波豆（Ichthyobodo necator，广义，s.l.）已被证明代表了几个物种的复合体，不同鱼波豆属物种的流行病学知之甚少。因此，我们采用分子方法来确定在我们研究中检测到的寄生虫的具体身份。仅出现了最近重新定义和限定意义上的鱼波豆（Ichthyobodo necator，狭义，s.s.）。我们观察到感染呈现双峰模式；第一个峰值出现在3月的鱼苗中，第二个峰值出现在8月和9月的鱼种和准幼鲑中。在鱼种和准幼鲑身上观察到的皮肤损伤与鱼波豆感染显著相关。此外，这些感染与鱼的血细胞比容值（Hct）和条件因子（K）均呈负相关。养殖鲑鱼的感染模式表明，狭义鱼波豆是鲑鱼的机会性寄生虫，在有易感宿主且环境有利于寄生虫增殖的时期大量繁殖。我们的研究首次在野生捕获的成年鲑科鱼类（褐鳟Salmo trutta，L.）上检测和鉴定出狭义鱼波豆。在作为孵化场水源的湖泊中捕获的野生鲑科鱼类和刺鱼（Gasterosteus aculeatus，L.）被发现感染了狭义鱼波豆，因此这些可能是寄生虫通过进水口进入孵化场的来源。
