ANNULATE LAMELLAE AND "YOLK NUCLEI" IN OOCYTES OF THE DRAGONFLY, LIBELLULA PULCHELLA

Annulated membranes in the form of single and short lamellae are present adjacent to and parallel to the nuclear envelope in oogonia and early oocyte (synaptene) stages of the dragonfly, Libellula pulchella. These solitary and short annulate lamellae are usually continuous with long, part rough- and part smooth-surfaced cisternae which extend into more distal areas of the oogonial ooplasm. These particular annulate lamellae then either disappear or decrease in number to be replaced by a much more extensive system of annulate lamellae in the cortical ooplasm of previtellogenic oocytes. The differentiation of extensive stacks of annulate lamellae is consistently observed to be restricted to large cytoplasmic areas of considerable electron density. These cytoplasmic regions consist of material which stains basophilic and contains RNA but differs structurally from the large number of ribosomes which surround the dense masses. The cytoplasmic dense masses, in terms of their formation and staining reactions, are comparable to the "yolk nuclei" or "Balbiani bodies" described in insect oocytes in earlier studies. The results of the present study thus provide evidence that the appearance of cortical ooplasmic stacks of annulate lamellae in the dragonfly oocyte is specifically limited to cytoplasmic areas of high electron density which contain RNA but which do not have a ribosomal morphology.