钉螺体内日本血吸虫尾蚴发育期的形态及其扫描电镜观察

本文通过活体标本、连续切片、全封标本及扫描电镜观察了大陆品系日本血吸虫Schistosomajaponicum子胞蚴体内尾蚴发育期的形态。日本血吸虫尾蚴发育分为五期,即胚细胞期、胚球期、尾蚴雏体期、成熟前期和成熟期。与曼氏血吸虫尾蚴发育进行比较,日本血吸虫尾蚴在胚球期无极化现象;尾蚴雏体期的尾芽形态多非圆球形,尾叉形成较早。钻腺及焰细胞均在此期发生,较曼氏血吸虫尾蚴早。除了上述头器、头腺、钻腺、焰细胞及消化器官进一步发育外,体内散在胚细胞结集为生殖始基,体表感觉乳突分化与体尾肌细胞的发育,尾蚴从成熟前期过渡到成熟期。 电镜首次原位观察尾蚴发育在子胞蚴育腔内的自然状态。尽管偶尔可见到胞蚴体壁与胚元之间某些结构联系,但大部份的胚元各自独立混杂在育腔之中。此外尚注意到尾蚴体棘发生在成熟前期,但其密度较成熟尾蚴小,而其大小却比成熟尾蚴的大。尾蚴头器上感觉乳突和围褶可能先于内部腺体细胞的分化。

MORPHOLOGICAL OBSERVATIONS ON THE DEVELOPING CERCARIA OF SCHISTOSOMA JAPONICUM BY LIGHT AND SCANNING ELECTRON MICROSCOPE

This article reports the morphological abservations on the developing cercaria of Sch-istosoma japonicum from daughter spororyst in the intra molluscan host, Oncomelania hu-pensis. The materials studied involved fresh living organisms, paraffin series sections, whole mount and SEM specimens. The process of cercarial development may be divided into 5 stages, e.i.Sl, germinal cell; S2, germinal ball; S3, Embryo-tail budding; S4, prematured stage and S5, fully developed stage. The differences between the development of S. japonicum and 5. mansoni were compared. The developmental characteristics of S. japonicum indicated: 1) there was no conglomerated polarization of germinal cells during S2, 2) the tail bud was not in spherical form and forked tail formation was earlier than that of S. mansoni, 3) five pairs of penetrated glands and four pairs of flame cells developed at the same time during S3, 4) the development continued with the formation of glands (head and penetrated glands), organs (digestive, head and osmo-regulatory systems), primordal genital anlagen and sensory papilla as well as muscle cells of the body and tail, and 5) the cercaria became highly active and completed its development process from the prematured stage, S4 to fully matured stage, S5The natural situation of the germinal elements in the brood chamber of daughter sporo-cyst was revealed for the first time by means of SEM. Although a tube-like structure connecting between the sporocyst wall and germinal elements could be seen occasionally, most of the cercarial embryoes were segregated free in the brood chamber of the sporocyst. Tegumental spines could be identified in prematured stage (S4), but the density of the spines was less and the size bigger than that in the matured stage (S5). Probably, the sensory papillae and the folds of the head organ were differentiated prior to the gland cell inside the organism.