PHYLOGENETIC SIGNIFICANCE OF THE STRUCTURE OF ADULT OVARY AND OOGENESIS IN A PRIMITIVE CHILOGNATHAN DIPLOPOD, HYLEOGLOMERIS-JAPONICA VERHOEFF (GLOMERIDA, DIPLOPODA)

Some histological details of the adult ovary of Hyleoglomeris japonica are described for the first time in the glomerid diplopods. The ovary is a single, long sac-like organ extending from the 4th to the 12th b ody segment along the median body axis, lying between the alimentary c anal and the ventral nerve cord. The ovarian wall consists of a layer of thin ovarian epithelium which surrounds a wide ovarian lumen. A pai r of longitudinal ''germ zones,'' including female germ cells, runs in the lateral ovarian wall. Each germ zone consists of two types of oog enetic areas: 1) 8-12 narrow patch-shaped areas for oogonial prolifera tion, arranged metamerically in a row along each of the dorsal and ven tral peripheries, and 2) the remaining wide area for oocyte growth. Oo gonial proliferation areas include oogonia, very early previtellogenic oocytes, and young somatic interstitial cells, among the ovarian epit helial cells. The larger early previtellogenic oocytes in the oogonial proliferation areas are located nearer to the oocyte growth area, and migrate to the oocyte growth area. They are surrounded by a layer of follicle cells and are connected with the ovarian epithelium of the oo cyte growth area by a portion of their follicles. They grow into the o varian lumen, but their follicles are still connected with the oocyte growth area. Various sizes of the previtellogenic and vitellogenic ooc ytes in the ovarian lumen are connected with the oocyte growth area; t he smaller oocytes are connected nearer to the dorsal and ventral oogo nial proliferation areas, while the larger ones are connected nearer t o the longitudinal middle line of the oocyte growth area. Following th e completion of vitellogenesis and egg membrane formation in the large st primary oocytes, the germinal vesicles break down. Ripe oocytes are released from their follicles directly into the ovarian lumen to be t ransported into the oviducts. Ovarian structure and oogenesis of H. ja ponica are very similar to those of other chilognathan diplopods. At t he same time, however, some characteristic features of the ovary of H. japonica are helpful for understanding the structure and evolution of the diplopod ovaries. Some aspects of the phylogenetic significance i n the paired germ zones of H. japonica are discussed. (C) 1997 Wiley-L iss, Inc.