The sexual dimorphic inguinal glands of the frog species Ololygon centralis (Anura: Hylidae) at light and transmission electron microscopy

ABSTRACT The anuran skin characteristically has different types of glands, most of which are microscopic and are spread throughout the skin. Some species have specialized regions where glands agglomerate, forming macroglands. The description of the external morphology of Ololygon centralis (Pombal & Bastos, 1996) revealed the presence of an inguinal gland. Ololygon centralis is the only species of the genus that has a macrogland. The present study found these inguinal macroglands to be present only on male specimens, thus characterizing it as a sexually dimorphic skin gland. Microscopic analysis revealed that these glands are composed of many syncytial units involved by myoepithelial cells. The center of the syncytium is full of a proteinaceous secretion with a basic pH and the absence of sugar residues. Similar glands observed in other anuran species have been associated with pheromone production, suggesting that the inguinal glands described for O. centralis males may have a similar function.摘要：无尾两栖动物的皮肤通常具有多种类型的腺体，其中绝大多数为显微结构，广泛分布于皮肤各处。部分物种的皮肤存在特化区域，腺体在此聚集形成巨腺（macroglands）。对中央棱蟾（Ololygon centralis，Pombal & Bastos, 1996）的外部形态学研究显示，该物种具有腹股沟腺。中央棱蟾是其所在属中唯一拥有巨腺的物种。本研究发现，这类腹股沟巨腺仅存在于雄性个体中，由此将其归类为性二态皮肤腺。显微分析显示，该腺体由大量被肌上皮细胞包裹的合胞体单元构成；合胞体的核心区域充满呈碱性pH值且不含糖残基的蛋白质分泌物。在其他无尾两栖类物种中观察到的同类腺体已被证实与信息素生成相关，这暗示本次在雄性中央棱蟾中描述的腹股沟腺可能具备类似功能。