Embryogenesis and the first-stage larva of Thelazia lacrymalis
Embryogenesis and the first-stage larva of Thelazia lacrymalis
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DOI：
10.1079/joh2003167
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发表时间：
2003-09
影响因子：
1.6
通讯作者：
H. Dongus;P. Beelitz;H. Schöl
中科院分区：
文献类型：
--
作者：
H. Dongus;P. Beelitz;H. Schöl
摘要利用光学显微镜和扫描电镜观察了泪囊线虫（Thelaziacrymalis，线虫纲：Thelaziidae）雌性生殖系统的发育阶段和受精卵的沉积阶段。雌性T.泪囊虫具有双卵型和后卵型生殖系统，具有成对的卵巢、输卵管和子宫以及单个阴道和外阴。圆形和纺锤形的初级卵母细胞分别在卵巢和输卵管内。每个子宫的远端提供了一个充满精子的受精室，随后是一个括约肌样部分。进一步向前，子宫逐渐变宽，包含分裂的受精卵，小的和大的桑椹胚，蝌蚪期胚胎和马蹄形胚胎，其长度增加，变得更细，形成椒盐卷饼期胚胎和卷起的幼虫。幼虫逐渐伸展，最后伸直，但仍然覆盖着阴道中的卵膜。卵膜包裹整个幼虫，在幼虫的尖尾处扩大，形成球状。在扫描电镜水平上，第一阶段的幼虫显示有一个终端口和三个钩指向后方和条纹角质层。在感染弓形虫的马结膜囊灌洗液中也发现了形态相同的幼虫。lacrymalis，这种线虫物种可以被描述为卵胎生的。
Abstract The female reproductive system of Thelazia lacrymalis (Nematoda: Thelaziidae) was investigated by light and scanning electron microscopy (SEM) with regard to the developmental stages and the stage deposited by the gravid nematode. Female T. lacrymalis have a didelphic and opisthodelphic type of reproductive system with paired ovaries, oviducts and uteri and a single vagina and vulva. Round and spindle-shaped primary oocytes are documented within the ovaries and oviducts, respectively. The distal part of each uterus provides a fertilization chamber filled with spermatozoa, followed by a sphincter-like part. Further anterior, the uteri broaden gradually containing dividing zygotes, small and large morulae, tadpole-stage embryos and horseshoe-shaped embryos which increase in length and become slimmer forming pretzel-stage embryos and larvae rolled up. The larvae stretch gradually and finally lie straight but still covered with their egg membrane in the vagina. The egg membrane encloses the whole larva and is enlarged at the pointed tail of the larva forming a bulb. At the SEM level, the first-stage larva is shown to have a terminal mouth and three hooks directed posteriorly and a striated cuticle. As morphologically identical larvae were also found in lavages of the conjunctival sac of horses infected with T. lacrymalis, this nematode species can be described as ovoviviparous.