松材线虫生殖系统发育研究

[Objective]There is a significant northward and westward expansion of pine wilt disease,posing a serious threat to the country's forest and ecological security in China.Studying the development of the reproductive system of B.xylophilus at the cellular level is crucial for a systematic understanding of the nematode's development and rapid reproduction processes.This will be fundamental to effectively curbing the spread of pine wilt disese.[Method]The gonads and sex organs of B.xylophilus at different stages of development were dissected and observed by light microscopy.Morphological features of the reproductive system from B.xylophilus were carefully recorded and photographed.Additionally,The important quantitative data are counted.[Results]The gonads of J2 larvae were'barrel-shaped',consisting of four cells located at 56.37%of the body length ventrally.These four cells,named Z1,Z2,Z3,and Z4 from anterior to posterior,can proliferate and differentiate into the entire adult gonadal organ under the condition of 25°C for 72 hours,referred to as the'gonadal primordium'.Notably,during the middle to late stages of J3,the female gonads looked like'shuttle-shaped'.These four cells are also known as the'genital primordium'.As the nematode develops into the middle to late J3 stage,differences between male and female gonads begin to appear:the female gonad becomes'pike-shaped'and extends both anteriorly and posteriorly,whereas the anterior part of the male gonad bends backward.At the early stages of J4,the distinction between males and females becomes more clearly.At this stage,four epidermal cells located at 70%of the female body length begin to divide,eventually forming the adult vulva by inward division and compression.At the end of the J4 stage,the anchor cell(ac)in the gonad above the female vulva undergoes programmed cell death,connecting the gonad to the external environment through the vulva.Similarly,the linker cell(lc)near the male gonad undergoes programmed cell death,establishing a connection between the gonad and the external environment via the cloaca.In the adult stage,the female reproductive system comprises the ovary,spermatheca,uterus,vulva,and post-vulval sacs,whereas the male reproductive system includes the testis,seminal vesicle,ejaculatory duct,and spicule[Conclusion]In the egg and J1 stages of B.xylophilus,the morphological characteristics of the nematode gonads are indiscernible.From the J2 to the middle J3 stages,there are no observable differences between males and females.However,from the middle J3.to the J4 stage,the sexes can be differentiated based on gonadal morphology.In the adult stage,the differences between males and females become more pronounced,with fully developed male and female reproductive systems.