<p>The dermal glands of the freshwater mite <i>Sperchon (Hispidosperchon) clupeifer</i> Piersig, 1896 (Acariformes, Sperchonidae) were studied using light optical (LO), scanning (SEM), and transmission (TEM) electron microscopy, and confocal laser microscopy (CLSM). Fifteen pairs of dermal glands were organized identically. They occupied a large body volume between the integument and the midgut. All glandularia (the gland openings), except for the preantennal glandularia 1 (A1) were accompanied by a long slim seta. A short stout and branched seta accompanied the preantennal glandularia. The gland openings were formed from two paired valves—one larger outer and one smaller inner—protruding outwards. Internally, the valves diverge to the sides forming a unique system of the internal sclerites (the so-called cuticular loops) and membranes, to which muscles attach. The gland alveolus was composed of tightly packed cells, which did not leave the intra-alveolar lumen. The cells contained large electron-dense granules, which, in turn, were packed with smaller round crystal-like inclusions. The cytoplasm included short and wavy RER cisterns and poorly organized Golgi-like bodies. The cells also contained electron-lucent vacuoles. Single muscle fibers underlined the gland body. Vesicular transport across the basal membrane was not detected. Both the secretory granules and the cytoplasmic matrix were accumulated and mixed within the area underneath the gland opening—the gland mouth. The identical organization of the gland openings observed in all water mites studied suggests a common origin of dermal glands and confirms the monophyly of the Hydrachnidiae.</p>