Comparative Observation On The Development And Reproduction Of Rhabditida Nematode

We did comperison among 4 species of Rhabditida nematodes belonging to 4genus,3 families.This paper focuses on nematode development and reproductionwith the following aspects:1)early embryogenesis,2)development of reproductiveorgan and 3)the process of oogenesis.See more details below.The nematodes we studied were Distolabrellus veechi,Mesorhabditis sp.,Panagrolaimus sp.and Acrobeloides sp..In all of these nematodes,the type of initialcleavage are clear asymmetric.,named"strong expression of the germ line".Eachnematode under go the process of egg cleavage,blastula,gastrula and organogenesisduring prenatal development which leads to the development of a juvenile.Theduration of early embryonic cell cycles and early cleavages can vary considerablyamong species.In Panagrolaimus sp.and Acrobeloides sp.,they almost feature the same type ofstructure of reproductive system in some degree:a single anterior arm,vulva atmid-body.In Mesorhabditis sp.and Distolabrellus veechi,they feature the other typeof structure of reproductive system:a single anterior arm,vulva far posterior.As such,comparative developmental biology were done to investigate changes in gonadal armmigration that result in these two types of reproductive systems.The reproductive mode of Distolabrellus veechi,Mesorhabditis sp.andPanagrolaimus sp.was confirmed as gamogenesis,and Acrobeloides sp.wasconfirmed as parthenogenesis.For four nematodes,chromosomes in the germ line nuclei were visualized byDAPI in situ staining of dissected adult female gonadal arms.In order to analyze theunderlying mechanism that accompany parthenogenetic nematode Acrobeloides sp.,the oogenesis procedure across gamogenic nematode and parthenogenic nematodewere investigated.According to our results,1)the chromosome number ofAcrobeloides sp.has no change between oogonium and oocyte;2)show no featuresabout homologous chromosome pairing in Acrobeloides sp.;3)only one meiotic division take place and only one polar body are generated in Acrobeloides sp.,weconclude that the truncated meiosis for Acrobeloides sp.enables the egg cell nucleusto retain a diploid status without fusion with a sperm.