Sliusarev G S, Cherkasov A S
Parazitologiia. 2001 Jul-Aug;35(4):338-43.
In the present study authors claim that the adult orthonectids can not move through host tissues by themselves. In various species of these enigmatic parasites there are at least two different mechanisms of emission of males and females from the host body. Intoshia linei, the orthonectid from Lineus ruber (Heteronemertini), and Intoshia variabili, the parasite of a flatworm Macrorhynchus crocea, realize the first way of emission. The plasmodium of these species forms tube-like outgrowths, which pierce the host tissues reaching the host body surface. The cytoplasm structure of these outgrowths differs from the cytoplasm of the central mass of plasmodium. Small mitochondria with electron dense matrix, lipid granules and vesicular bodies being common in the central part are absent in these outgrowths. Plasmodial outgrowths reach the host body surface and adult orthonectids move inside them using their cilia and stopping from time to time. The plasmodial outgrowths penetrate the ciliated epithelium, then males and females leave the host. Duration of emission may vary in different species from 6 to 13 days. The second mechanisms of emission is common for the orthonectid parasites of mollusks. Our observations of Rhopalura philinae from the gastropod Philine scabra lead to the conclusion that males and females leave their host practically simultaneously. When the plasmodium attains the terminal stage of its development most of the host entrails are already displaced by plasmodial mass. It causes breaks in host body walls and hence to emission of sexual individuals. During this process, which lasts about 24 hours, the mollusk dies. The same mechanism was observed in Rhopalura littoralis--parasite of the gastropod Onoba aculeus. Our investigations of emission ways reveal that the plasmodium of orthonectids has a potency of directing growth and can form certain structures. The process of forming the plasmodial outgrowths is coordinated in time and space. These outgrowths have certain directions inside the host body and the maturation of sexual individuals is clear related with the development of plasmodium outgrowth system. Our results suggest that forming of plasmodial outgrowths is an element of development of the united and highly integrated system. It is necessary to emphasize the capability of plasmodium to accomplish such morphogenetic transformations. This fact argues that plasmodium is a part of parasite organism and not host cells modified, like some experts supposed.
在本研究中，作者声称成年直泳虫无法自行在宿主体内移动。在这些神秘寄生虫的不同物种中，至少存在两种将雄性和雌性排出宿主体外的不同机制。来自红纽虫（异纽虫科）的直泳虫林氏内托虫，以及扁形虫巨吻涡虫的寄生虫可变内托虫，实现了第一种排出方式。这些物种的疟原虫形成管状突出物，穿透宿主体组织到达宿主身体表面。这些突出物的细胞质结构与疟原虫中央团块的细胞质不同。中央部分常见的带有电子致密基质的小线粒体、脂质颗粒和囊泡体在这些突出物中不存在。疟原虫突出物到达宿主身体表面，成年直泳虫利用其纤毛在其中移动并不时停下。疟原虫突出物穿透纤毛上皮，然后雄性和雌性离开宿主。不同物种的排出持续时间可能从6天到13天不等。第二种排出机制在软体动物的直泳虫寄生虫中很常见。我们对来自腹足纲糙海兔的菲氏红帕虫的观察得出结论，雄性和雌性几乎同时离开它们的宿主。当疟原虫发育到末期时，大部分宿主内脏已被疟原虫团块取代。这导致宿主体壁破裂，从而使有性个体排出。在这个持续约24小时的过程中，软体动物死亡。在滨海红帕虫（腹足纲尖刺欧诺巴的寄生虫）中也观察到了相同的机制。我们对排出方式的研究表明，直泳虫的疟原虫具有引导生长的能力，并能形成特定结构。疟原虫突出物的形成过程在时间和空间上是协调的。这些突出物在宿主体内有特定方向，有性个体的成熟显然与疟原虫突出物系统的发育有关。我们的结果表明，疟原虫突出物的形成是一个统一且高度整合系统发育的一个要素。有必要强调疟原虫完成这种形态发生转变的能力。这一事实表明疟原虫是寄生虫生物体的一部分，而不是像一些专家所认为的那样是被修饰的宿主细胞。
