Su Xiaohong, Yang Xiaojuan, Li Jing, Xing Lianxi, Liu He, Chen Jiaoling
Shaanxi Key Laboratory for Animal Conservation, Northwest University, Xi'an, China.
Key Laboratory of Resource Biology and Biotechnology in Western China, Ministry of Education, Northwest University, Xi'an, China.
Evol Dev. 2017 Jul;19(4-5):218-226. doi: 10.1111/ede.12229.
Termite workers are characterized by unique flexibility in that a worker can develop in one of three ways: remain a worker, become a soldier within two successive moults, or become a neotenic reproductive (NR) within a single moult. However, is it true that workers can transform into NRs within a single moult? Actually, the developmental pathways of workers turning into NRs remains unclear. In this study, we show for the first time that the female workers of Reticulitermes labralis develop into NRs after a pre-NRs stage. We found that a female worker became a NR after two successive moults, whereas the male workers copulated directly with queens without undergoing any moults. After the first moult led the female workers into the pre-NR stage, the length of their abdomens, seventh sternites and ovaries significantly increased. After the second moult from the pre-NRs stage into NRs, the follicle cells returned to normal, and a few oocytes and follicle cells underwent apoptosis. These results demonstrated that the female pre-NR type was a transitional type during the development of female workers to the NR caste, and the starting point for oogenesis resumption was the NR stage. We confirmed there were fundamental differences in the reproductive pathway of the male and female workers. Therefore, we determined that the transformation process of the female NRs from workers may be a very complex process, and the reproductive biology of the workers has great potential to provide important and spectacular insights into the evolution strategy of termites.
白蚁工蚁的特点是具有独特的灵活性，即一只工蚁可以通过三种方式之一发育：保持为工蚁、在连续两次蜕皮后成为兵蚁，或在单次蜕皮后成为幼态生殖蚁（NR）。然而，工蚁真的能在单次蜕皮内转变为幼态生殖蚁吗？实际上，工蚁转变为幼态生殖蚁的发育途径仍不清楚。在本研究中，我们首次表明，黄胸散白蚁的雌性工蚁在经历一个幼态生殖蚁前期阶段后发育为幼态生殖蚁。我们发现，雌性工蚁在连续两次蜕皮后成为幼态生殖蚁，而雄性工蚁直接与蚁后交配，无需经历任何蜕皮。在第一次蜕皮使雌性工蚁进入幼态生殖蚁前期阶段后，它们的腹部、第七腹板和卵巢长度显著增加。在从幼态生殖蚁前期阶段到幼态生殖蚁的第二次蜕皮后，卵泡细胞恢复正常，一些卵母细胞和卵泡细胞发生凋亡。这些结果表明，雌性幼态生殖蚁前期类型是雌性工蚁发育为幼态生殖蚁等级过程中的一种过渡类型，卵子发生恢复的起点是幼态生殖蚁阶段。我们证实了雄性和雌性工蚁的生殖途径存在根本差异。因此，我们确定雌性工蚁向幼态生殖蚁的转变过程可能是一个非常复杂的过程，工蚁的生殖生物学有很大潜力为白蚁的进化策略提供重要且引人注目的见解。
