Female and male reproductive systems in the oribatid mite Hermannia gibba (Koch, 1839) (Oribatida: Desmonomata)

The reproductive systems of both sexes of the oribatid mite, Hermannia gibba, are described. In females, the unpaired ovary contains two clusters of early and middle previtellogenic oocytes. Germ cells in each cluster are interconnected via microtubule-rich protrusions forming the so-called medulla. Oviducts are paired and enter the lateral parts of an unpaired uterus; the middle part of the uterus is narrow and forms a short uterine canal passing into a cuticle-lined ovipositor canal. In males, paired testes are divided into germinal and glandular parts, termed the germinal testis and glandular testis, respectively. Germinal testes are made up of somatic cells in which numerous groups of developing germ cells are embedded. After meiosis, nuclear material condenses, forming a chromatin body surrounded by cytoplasm containing bowl bodies and mitochondrial derivatives. Spherical aflagellate spermatozoa are released into the lumen of the testis in which their surfaces are coated by additional electron-dense material. Short, paired deferent ducts coalesce and empty into a short ejaculatory duct opening at the genital orifice. Bacterial microorganisms were found in the gonads of some individuals of both sexes. Microorganisms colonize the oocytes of females, whereas in males they are present both between and within spermatocytes and spermatids. Their role in both sexes, as well as possible vertical transmission via males, is unclear.