Owing to their incomplete adaptation to the terrestrial environment, amphibians possess complex cutaneous glandular systems. The skin glands not only regulate water loss and respiratory gas and salt exchange, but are also involved in defense against predators and microorganisms, social communication, and reproduction. These glands are distributed throughout the integument, but can accumulate in specific regions, forming visible outgrowths known as macroglands. Some macroglands are sexually dimorphic and mediate intersexual communication and reproductive success. The postaxillary gland is a sexually dimorphic macrogland in Nidirana pleuraden. Its biological function and its morphological and histochemical characteristics are unclear. In the present study, we describe the structure and ultrastructure of the postaxillary gland, and explore its main function. The postaxillary gland has a thinner epidermis than the dorsal region of N. pleuraden. In addition to ordinary serous glands (OSG), type I and II mucous gland (I MG & II MG), a type of specialized mucous gland (SMG) is also found to constitute the postaxillary gland. The SMG is larger than other gland types, and consists of high columnar mucocytes with basal nuclei arranged radially toward a lumen. SMGs are positive to periodic acid-Schiff stain and stained blue in Masson’s trichrome stain. A discontinuous myoepithelial sheath lacking innervation encircles SMG mucocytes, and the outlets of such glands are X- or Y-shaped. Transmission electron microscopy reveals abundant secretory granules in SMG, which are biphasic, composed of an electron-opaque outer ring and a less electron-dense core. Lipid droplets, and organelles, such as rough endoplasmic reticulum and Golgi stacks, are located in the supranuclear cytoplasm of the mucocytes in SMG. Female N. pleuraden exhibits chemotaxis toward homogenate of the postaxillary gland, but male does not. On treatment with trypsin, this sexual attraction disappears. The postaxillary gland of N. pleuraden is a male-specific macrogland that consists primarily of SMGs, together with OSGs, I MGs and II MGs. Other than their extremely large size, SMGs structurally and histochemically resemble many reported specialized gland types in amphibian sexually dimorphic skin glands. Secretions of the postaxillary gland are proteinaceous sexual pheromones, which are believed to attract females at male calling intermissions.

中文翻译：

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Nidirana pleuraden（两栖类：无尾目：Ranidae）腋后腺的结构和生物功能评估。


由于对陆地环境的不完全适应，两栖动物拥有复杂的皮肤腺系统。皮肤腺不仅调节水分流失和呼吸气体和盐的交换，还参与防御捕食者和微生物、社会交流和繁殖。这些腺体分布在整个体被中，但可以在特定区域聚集，形成可见的增生，称为大腺体。一些大腺体具有两性二态性，介导两性交流和生殖成功。腋后腺是 Nidirana pleuraden 中的性二态性大腺。其生物学功能及其形态和组织化学特征尚不清楚。在本研究中，我们描述了腋后腺的结构和超微结构，并探讨了其主要功能。腋后腺的表皮比胸膜神经背侧区域的表皮薄。除了普通浆液腺（OSG）、I型和II型粘液腺（I MG & II MG）外，还发现一种特殊的粘液腺（SMG）构成腋后腺。 SMG 比其他腺体类型大，由高柱状粘细胞组成，基底核朝管腔呈放射状排列。 SMG 对高碘酸希夫染色呈阳性，并在马森三色染色中呈蓝色。缺乏神经支配的不连续肌上皮鞘包围 SMG 粘细胞，此类腺体的出口呈 X 形或 Y 形。透射电子显微镜显示 SMG 中存在丰富的分泌颗粒，它们是双相的，由电子不透明的外环和电子密度较低的核心组成。 脂滴和细胞器，例如粗面内质网和高尔基体堆，位于 SMG 中粘细胞的核上细胞质中。雌性胸膜猪笼草对腋后腺匀浆表现出趋化性，但雄性则不然。在用胰蛋白酶治疗后，这种性吸引力就会消失。胸膜 N. pleuraden 的腋后腺是雄性特有的大腺，主要由 SMG 以及 OSG、I MG 和 II MG 组成。除了尺寸极大之外，SMG 在结构和组织化学上与许多报道的两栖动物两性二态性皮肤腺中的特殊腺体类型相似。腋后腺的分泌物是蛋白质性信息素，据信在雄性叫声间歇时吸引雌性。