DNA accumulation during oogenesis in the free-living nematode Panagrellus silusiae

Abstract

DNA contents of nuclei at different stages of gonadogenesis, gametogenesis and embryogenesis in the free-living nematode Panagrellus silusiae were measured by Feulgen microspectrophotometry. Somatic nuclei of gonadal tissue in both males and females have DNA values that range from 2C to 4C. Relative DNA values identified meiotic processes during spermatogenesis. In the adult female, developing oocytes amass an amount of nuclear DNA in excess of the expected 4C equivalent. The chromatin of these nuclei is diffuse with varyingsized clumps of Feulgen-positive material. Throughout oogenesis maturing oocytes remain uninucleolate. — The extra oocyte DNA is distributed proportionately at each of the first four cleavage divisions; thereafter, its presence is not resolvable. — A standardized microphotometric comparison indicated that the amount of DNA in the unit genome of P. silusiae is about 0.1 pg. The oviduct oocytes accumulate about 3.6 pg DNA in excess of a 4C equivalent. The kind of DNA that builds up during oogenesis in this organism is not known.