背景:在欧洲,tape虫Dibathroocephaluslatus(syn。Diphyllobothriumlatum)是众所周知的人类二苯基病的病因,通过食用被plerocercoids感染的生鱼肉(tape虫的幼虫期)传播。然而,在中间宿主和确定宿主中寄生虫的建立过程知之甚少。这项研究主要针对该物种的角砾岩的头节(前部),这有助于寄生虫在中间paratenic鱼宿主中的渗透,随后它附着在最终宿主的肠道上。
方法:从意大利高山湖泊中捕获的欧洲鲈鱼(Percafluviatilis)的肌肉组织中分离出Plerocercoids。使用共聚焦显微镜检查寄生虫,扫描电镜(SEM)和透射电镜(TEM)。对整个幼虫进行免疫荧光标记。
结果:中枢神经系统和周围神经系统的组织被捕获。包括具有大的致密神经分泌颗粒的神经细胞的超微结构。两种类型的神经纤维从身体表面向位于bothria两侧的实质中的神经丛延伸。这些纤维中的一种被发现是5-羟色胺能的,并且具有大的亚表神经细胞体。发达的腺体装置,发现于整个plerocorcoid薄壁组织,产生的异质颗粒具有透明的核心填充在致密层中。在D.latus的plerocercoids的脊柱和体表上发生了三种不同类型的微裂片:(i)钩刺;(ii)圆锥形脊柱;(iii)毛状丝状。在外皮的远端细胞质和下面的肌肉组织之间观察到非纤毛感觉受体。
结论:共聚焦激光扫描显微镜和电子显微镜(SEM和TEM)显示出神经系统的详细显微解剖结构,与成虫D.latus相比,幼虫阶段也有一些差异。这些特点,即发育良好的腺体系统和巨大的钩形钩刺,因此,可能是居住在鱼类宿主中的plerocercoids以及它们在人类肠道中的感染后附着所必需的。
BACKGROUND: In Europe, the tapeworm Dibothriocephalus latus (syn. Diphyllobothrium latum) is a well-known etiological agent of human diphyllobothriosis, which spreads by the consumption of raw fish flesh infected by
plerocercoids (tapeworm\'s larval stage). However, the process of parasite establishment in both intermediate and definitive hosts is poorly understood. This study was targeted mainly on the scolex (anterior part) of the plerocercoid of this species, which facilitates penetration of the parasite in intermediate paratenic fish hosts, and subsequently its attachment to the intestine of the definitive host.
METHODS: Plerocercoids were isolated from the musculature of European perch (Perca fluviatilis) caught in Italian alpine lakes. Parasites were examined using confocal microscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Immunofluorescence tagging was held on whole mount larvae.
RESULTS: The organisation of the central and peripheral nervous system was captured in D. latus
plerocercoids, including the ultrastructure of the nerve cells possessing large dense neurosecretory granules. Two types of nerve fibres run from the body surface toward the nerve plexus located in the parenchyma on each side of bothria. One type of these fibres was found to be serotoninergic and possessed large subtegumental nerve cell bodies. A well-developed gland apparatus, found throughout the plerocercoid parenchyma, produced heterogeneous granules with lucent core packed in a dense layer. Three different types of microtriches occurred on the scolex and body surface of
plerocercoids of D. latus: (i) uncinate spinitriches; (ii) coniform spinitriches; and (iii) capilliform filitriches. Non-ciliated sensory receptors were observed between the distal cytoplasm of the tegument and the underlying musculature.
CONCLUSIONS: Confocal laser scanning microscopy and electron microscopy (SEM and TEM) showed the detailed microanatomy of the nervous system in the scolex of
plerocercoids, and also several differences in the larval stages compared with adult D. latus. These features, i.e. well-developed glandular system and massive hook-shaped uncinate spinitriches, are thus probably required for plerocercoids inhabiting fish hosts and also for their post-infection attachment in the human intestine.