Histological and immunohistochemical study of the ovaries and oviducts of the juvenile female of Caiman latirostris (Crocodilia: Alligatoridae)

ABSTRACT The purpose of this study was to examine the ovaries and the oviduct of juvenile females of the broad-snouted caiman, Caiman latirostris (Daudin, 1802), using light microscopy, histochemical and immunocytochemical techniques. The ovarian cortex was observed to contain groups of germinative cells and abundant previtellogenic follicles at different stages of development. In previtellogenic follicles, the oocyte was surrounded by a single cuboidal layer of granulosa cells, supported by the theca layer. The theca was formed by a concentric layer containing collage nous fibers, predominantly type I, and several smooth muscle fibers. The inner perivitelline layer appeared as a narrow basophilic region between the oocyte and the granulosa. The ovarian medullary region of loose connective tissue contained blood and lymphatic vessels, as well as numerous lacunae, being covered by a simple squamous epithelium, supported by a thin layer of connective tissue. The oviduct of C. latirostris showed five histologically distinct regions: infundibulum, magnum, isthmus, uterus and vagina. The infundibulum was composed of an irregularly folded mucosa covered by a simple columnar epithelium with the presence of ciliated cells, weakly reactive to PAS staining. In the magnum, the mucosa was highly folded, and pseudostratified columnar epithelium contains mucous cells, which reacted positively to PAS staining. The isthmus was lining by an epithelium of ciliated and non-ciliated secretory cells, but no gland was visualized in mucosa. In the uterus, the folded mucosa was composed of a simple epithelium of high cylindrical cells and the lamina propria, which was predominantly formed by strongly birefringent fibers, but yellow-green weakly birefringent fibers were also present. The epithelium of the vagina contained intensely ciliated and non-ciliated cells, both of which were positive to PAS staining and no gland was observed in this region. Although the ovary and the oviduct showed some morphological particularities, they are similar to other crocodilians.摘要 本研究旨在借助光学显微镜、组织化学及免疫细胞化学技术，对宽吻凯门鳄（Caiman latirostris，Daudin, 1802）幼年雌性个体的卵巢与输卵管开展观察分析。结果显示，卵巢皮质内存在生殖细胞团簇，以及大量处于不同发育阶段的卵黄发生前卵泡。在卵黄发生前卵泡中，卵母细胞被单层立方颗粒细胞包裹，该层细胞由卵泡膜层支撑。卵泡膜由同心排列的纤维层构成，主要成分为I型胶原纤维，并伴随大量平滑肌纤维。卵黄周内层表现为卵母细胞与颗粒细胞之间的狭窄嗜碱性区域。卵巢髓质由疏松结缔组织构成，内含血管、淋巴管及众多腔隙，其表面被覆单层扁平上皮，该上皮由薄层结缔组织支撑。 宽吻凯门鳄的输卵管在组织学上可划分为五个独立区域：漏斗部、膨大部、峡部、子宫部与阴道部。漏斗部黏膜呈不规则褶皱状，被覆单层柱状上皮，其中含有纤毛细胞，该细胞过碘酸-雪夫（Periodic Acid-Schiff，PAS）染色呈弱阳性反应。膨大部黏膜高度褶皱，其假复层柱状上皮内含有黏液细胞，该类细胞PAS染色呈阳性反应。峡部被覆由纤毛细胞与非纤毛分泌细胞构成的上皮，但黏膜内未观察到腺体结构。子宫部的褶皱黏膜由单层高柱状上皮及固有层构成，固有层主要由强双折射纤维组成，同时也存在少量黄绿色弱双折射纤维。阴道部上皮内含密集纤毛细胞与非纤毛细胞，两类细胞PAS染色均呈阳性，且该区域未观察到腺体。 尽管本研究观测到的卵巢与输卵管存在一定形态学特异性，但它们与其他鳄类动物的相应结构基本相似。