两种散白蚁两性生殖与孤雌生殖胚胎发育比较研究

A comparative study of embryonic development between gamogenesis and parthenogenesis in two Reticulitermes termites( Isoptera: Rhinotermitidae)

【目的】探究散白蚁两性生殖胚胎和兼性孤雌生殖胚胎各自的发育特点。【方法】以黑胸散白蚁Reticulitermes chinensis和尖唇散白蚁R.aculabialis各自的受精卵(雌雄配对所产的卵)和未受精卵(雌雌配对所产的卵)为研究对象,采用激光共聚焦显微镜观测两种散白蚁的受精卵和未受精卵的卵裂状态,数码显微系统拍照观察卵的外部形态变化。【结果】黑胸散白蚁蚁后所产的受精卵和未受精卵在巢中均能进行卵裂,但是未受精卵在24和48 h时的卵核数无显著性差异,而受精卵卵核数在24和48 h时有显著性差异;15 d时未受精卵的体积没有发生显著变化,而受精卵的体积显著性增大;15-20 d时未受精的蚁卵死亡,而受精卵正常发育。尖唇散白蚁受精卵和未受精卵在相同的时间段内卵核数没有显著性差异,48 h时的卵核数明显比24 h时多;第10天时受精卵长度和宽度发生显著性变化,同时体积也明显增大,而未受精卵在第15天时长度和宽度才开始发生显著性变化,同时体积也开始显著增大。【结论】具有兼性孤雌生殖能力的尖唇散白蚁,受精卵和未受精卵卵裂速度相同,但受精卵外形体积变化比未受精卵早。黑胸散白蚁未受精卵能继续进行卵裂,但发育异常,不能孵化;两种白蚁卵发育过程中卵的长度和宽度同时发生变化。黑胸散白蚁孤雌卵的卵裂特性可能是白蚁两性生殖向兼性孤雌生殖进化的过渡适应阶段。

【Aim 】 This study aims to explore the characteristics of embryonic development between gamogenesis and parthenogenesis in Reticulitermes. 【Methods】Fertilized eggs（ female-male paired eggs,FM eggs） and unfertilized eggs（ female-female paired eggs,FF eggs） were used for observing egg cleavage in two termite species,Reticulitermes chinensis and R. aculabialis. We used laser scanning confocal microscope for egg cleavage observation and digital microscope for observing external morphology of eggs and embryos. 【Results】Fertilized and unfertilized eggs from queens of R. chinensis could all cleave in the nest. Comparison between the nuclei of FF and FM eggs in 24 and 48 h revealed no significant difference in the number of nuclei for FF egg,but significant difference for FM egg. On the15 th day of egg development,no significant changes occurred in the volume of FF egg,whereas the volume of FM egg significantly increased. The FF eggs died on the 15th- 20 th day,while the FM eggs were in normal development. There was no significant difference in the number of nuclei in the same period between the fertilized and unfertilized eggs of R. aculabialis,and the number of nuclei in 48 h was significantly more than that in 24 h. The length and width of the fertilized eggs significantly changed on the 10 th day,with the volume significantly increasing at the same time. The increase of length,width and volume of unfertilized eggs,however,occurred on the 15 th day. 【Conclusion】The fertilized eggs and unfertilized eggs of facultative parthenogenesis R. aculabialis have the same cleavage rate. But the change in the shape of the fertilized eggs is earlier than that of the unfertilized eggs. Unfertilized eggs of R. chinensis can cleave,but have abnormal development,and can not hatch in the end. The length and width of eggs of these two termite species change simultaneously in the same development stage. The cleavage characteristics of FF egg of R. chinensis may be a preadaptive stage from bisexual reproduction to facultative parthenogenesis in termite reproductive evolution.