Palinauskas Vaidas, Žiegytė Rita, Ilgūnas Mikas, Iezhova Tatjana A, Bernotienė Rasa, Bolshakov Casimir, Valkiūnas Gediminas
Institute of Ecology, Nature Research Centre, Akademijos 2, Vilnius 2100, LT-08412, Lithuania.
Institute of Ecology, Nature Research Centre, Akademijos 2, Vilnius 2100, LT-08412, Lithuania.
Int J Parasitol. 2015 Jan;45(1):51-62. doi: 10.1016/j.ijpara.2014.08.012. Epub 2014 Oct 17.
For over 100 years studies on avian haemosporidian parasite species have relied on similarities in their morphology to establish a species concept. Some exceptional cases have also included information about the life cycle and sporogonic development. More than 50 avian Plasmodium spp. have now been described. However, PCR-based studies show a much broader diversity of haemosporidian parasites, indicating the possible existence of a diverse group of cryptic species. In the present study, using both similarity and phylogenetic species definition concepts, we believe that we report the first characterised cryptic speciation case of an avian Plasmodium parasite. We used sequence information on the mitochondrial cytochrome b gene and constructed phylogenies of identified Plasmodium spp. to define their position in the phylogenetic tree. After analysis of blood stages, the morphology of the parasite was shown to be identical to Plasmodium circumflexum. However, the geographic distribution of the new parasite, the phylogenetic information, as well as patterns of development of infection, indicate that this parasite differs from P. circumflexum. Plasmodium homocircumflexum n. sp. was described based on information about genetic differences from described lineages, phylogenetic position and biological characters. This parasite develops parasitemia in experimentally infected birds - the domestic canary Serinus canaria domestica, siskin Carduelis spinus and crossbill Loxia curvirostra. Anaemia caused by high parasitemia, as well as cerebral paralysis caused by exoerythrocytic stages in the brain, are the main reasons for mortality. Exoerythrocytic stages also form in other organs (heart, kidneys, liver, lungs, spleen, intestines and pectoral muscles). DNA amplification was unsuccessful from faecal samples of heavily infected birds. The sporogonic development initiates, but is abortive, at the oocyst stage in two common European mosquito species, Culex pipiens pipiens (forms pipiens and molestus) and Aedes vexans. Vectors of this Plasmodium sp. remain unknown.
100多年来,对鸟类血孢子虫寄生虫物种的研究一直依赖于其形态学上的相似性来建立物种概念。一些特殊情况还包括有关生命周期和孢子生殖发育的信息。目前已描述了50多种鸟类疟原虫物种。然而,基于PCR的研究表明血孢子虫寄生虫的多样性要广泛得多,这表明可能存在一群多样的隐性物种。在本研究中,我们使用相似性和系统发育物种定义概念,认为我们报告了首例已鉴定的鸟类疟原虫寄生虫隐性物种形成案例。我们利用线粒体细胞色素b基因的序列信息,构建了已鉴定疟原虫物种的系统发育树,以确定它们在系统发育树中的位置。在分析血液阶段后,该寄生虫的形态显示与环疟原虫相同。然而,这种新寄生虫的地理分布、系统发育信息以及感染发展模式表明,该寄生虫与环疟原虫不同。基于与已描述谱系的遗传差异、系统发育位置和生物学特征的信息,描述了新种同环疟原虫。这种寄生虫在实验感染的鸟类——家金丝雀Serinus canaria domestica、黄雀Carduelis spinus和交嘴雀Loxia curvirostra中引发寄生虫血症。高寄生虫血症引起的贫血以及脑中红细胞外期引起的脑麻痹是死亡的主要原因。红细胞外期也在其他器官(心脏、肾脏、肝脏、肺、脾脏、肠道和胸肌)中形成。从重度感染鸟类的粪便样本中进行DNA扩增未成功。在欧洲两种常见蚊子物种——尖音库蚊(包括pipiens和molestus型)和骚扰伊蚊中,孢子生殖发育在卵囊阶段开始,但发育不全。这种疟原虫物种的传播媒介仍然未知。