Morphological Changes of Salivary Glands in Hirudo nipponica before and after Feeding
BAO Liang1, WANG Zechong1, CAI Meixiang1, XING Yueting2, LUO Yuanyuan1*
To study the morphological and ultrastructural characteristics of salivary glands of Hirudo nipponica before and after feeding, the salivary glands of H. nipponica were observed by light microscope and electron microscope. Based on optical microscope imaging, it was observed that the pharynx of H. nipponica had a triangular muscle jaw, the salivary glands were attached to the jaw in a grape-like shape, and the glands were milky white and symmetrically distributed around the jaw. Results of HE staining showed that salivary gland cells were composed of ovoid somatic cells and elongated ducts, and the nuclei were located at the bottom or edge of the cells. The salivary gland cells of the unfed H. nipponica were lightly stained and the cytoplasm was plump; the salivary gland cells of the fed H. nipponica had dark staining and loose cytoplasm. Based on transmission electron microscopy imaging, spherical secretory granules were observed in salivary gland cells, and there was dense matter with high electron density inside the secretory granules. The salivary gland cells of the unfed H. nipponica were compact, the secretory granules squeezed each other, and a large number of secretory granules contained dense matter. However, the salivary gland cells of H. nipponica after feeding were loose in space, and there were gaps between secretory granules. Moreover, the dense matter in secretory granules disappeared. Based on scanning electron microscopy imaging, salivary gland cells were observed in a grape-like arrangement. The salivary gland cells of the unfed H. nipponica had smooth surface and rounded cells; the surface of the salivary gland cells of the fed H. nipponica had many extracellular particulates and the cells were pitted. The above results showed that various secretory proteins secreted by salivary gland cells were dense matter inthe secretory granules after H. nipponica were feeding, and most of the secretory granules were still in the salivarygland cells.
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