Ultrastructural aspects of vitellogenesis in Archegozetes longisetosus Aoki, 1965 (Acari, Oribatida, Trhypochthoniidae)
We studied the process of vitellogenesis in the oribatid mite Archegozetes longisetosus using light and electron microscopy. Both vitellogenesis and the formation of the first egg shell occur within the meroi of the ovary, starting after detachment from the medulla and completing with ovulation of the egg into the oviductal lumen at the ovarial bulb. Numerous microvilli appear on the surface, and abundant endocytotic pits and coated vesicles occur in the peripheral plasma of the oocyte. Accumulation of fatty yolk does not precede accumulation of proteineous yolk. Differentiation of ooplasm and formation of a perivitelline space beneath a continuous follicular epithelium were observed. Vitelline envelope material appears to be uniform. We compare details of vitellogenesis and propose a classification of the ovarian type as panoistic and the vitellogenesis as exogenic in A. longisetosus.
mite, oogenesis, yolk, transmission electron microscopy, microvilli, ovary