Abstract: 【Aim】 In order to investigate the characteristics of ovarian development and the starting point for resumption of oocyte development during the differentiation of female workers into neotenic reproductives (NRs) of Reticulitermes labralis. 【Methods】 The dynamic changes of ovary and oocyte during the development of female workers (from the 3rd instar to the 6th instar) and the differentiation of female workers into NRs of R. labralis were observed. Based on the transcriptome data of the development of primary reproductives and NRs from nymphs of R. labralis, genes involved in oocyte growth were identified and their expression levels during the differentiation of workers into NRs were detected using qRT-PCR method. 【Results】 The size of ovaries in workers of R. labralis increased gradually from early instar to late instar, the length and width of the ovaries of pre-neotenic reproductives (pre-NRs) were approximately 2- and 3-fold as long as those of workers, respectively, but did not increase significantly after the pre-NRs developed into NRs. After the workers developed into pre-NRs, there was no significant change in the size (long diameter) of oocytes and the thickness of the layer of follicle cells. However, after the pre-NRs developed into NRs, the size of oocytes and the thickness of the layer of follicle cells increased significantly. The expression levels of six genes involved in oocyte growth in NRs were extremely significantly increased. The expression levels of the six genes cyclin-dependent kinase 1, cell division cycle protein 20, G2/mitotic-specific cyclin-B3, G2/mitotic-specific cyclin-A, aurora kinase A and serine/threonine-protein kinase polo in NRs were approximately 34-, 62-, 91-, 36-, 57- and 106-fold as high as those in pre-NRs. After the workers developed into pre-NRs, only the expression levels of G2/mitotic-specific cyclin-B3, G2/mitotic-specific cyclin-A and aurora kinase A increased significantly, being approximately 3-, 3- and 2-fold in pre-NRs as high as in workers. 【Conclusion】 The ovarian development of R. labralis workers is arrested at late instar stage, and the oocyte development and meiotic resumption begin after the workers develop into NRs.

Key words: Reticulitermes labralis, workers, reproductive plasticity, oocyte, gene expression