The Development of Adultoid Reproductives and Brachypterous Neotenic Reproductives From the Last Instar Nymphs inReticulitermes labralis(Isoptera: Rhinotermitidae): A Comparative Study

Abstract

Secondary reproductives develop primarily from nymphs. However, they have been rarely studied; in particular, the development of adultoid reproductives (AR) with floppy wings is still unclear. In this study, the change in juvenile hormone (JH) levels, vitellogenin gene expression, and oogenesis during the development of AR and brachypterous neotenic reproductives (BN) from the last instar nymphs of Reticulitermes labralis are investigated and compared. The results showed that the AR derived from the last instar nymphs by molting, and they were more similar to neotenic reproductives in morphology. In addition, the paired AR were not able to survive in the absence of workers. In R. labralis, the process of the last instar nymphs developing into AR and BN took an increase in JH level as a starting point. The JH level of the last instar nymphs molting into BN was approximately 1.5-fold higher than that of the AR. Additionally, The JHIII level of BN peaked on day 5, and that of AR peaked on day 10, which induced the onset of vitellogenesis in BN and AR, respectively. After molting, the vitellogenin gene expression levels of both BN and AR initially increased and then declined, and the expression levels in the BN were significantly higher than those in the AR. In addition, the oocytes of BN matured earlier than those of the AR, and the number of eggs laid by the BN was higher than the number laid by the AR. Our results demonstrate that, in R. labralis, the last instar nymphs can develop into AR, which are significantly different from BN in their development.

Characterization of the transcriptomes and cuticular protein gene expression of alate adult, brachypterous neotenic and adultoid reproductives of Reticulitermes labralis

“…The presence of wings might lead to the conclusion that the R. labralis ANs are alate adults, but their overall appearance is more similar to that of secondary reproductives (neotenic reproductives). Additionally, our previous study demonstrated that R. labralis ANs and BNs are not able to survive in the absence of workers, whereas paired alate adults are able to create new colonies without the help of workers 4 5 . Therefore, ANs are more similar to neotenic reproductives in terms of morphology and behaviour.…”

“…In the absence of or at a great distance from the primary reproductives, a few of the nymphs or workers develop into secondary reproductives to provide for the continued or additional growth of the colony 1 2 . In R. urbis and R. labralis, the last instar nymphs can develop in three manners: (i) via a single moult into alate adults as primary reproductives, (ii) via a single moult into brachypterous neotenics as secondary reproductives, and (iii) via a single moult into adultoid reproductives with floppy wings as secondary reproductives 3 4 5 . Each reproductive caste exhibits a particular behavioural repertoire and caste-specific morphological characteristics depending on the environmental and social stimuli 2 .…”

Different strategies between queens and workers against fungal pathogens in the termite Reticulitermes chinensis

“…Once per week, we checked the consumption of a piece of moist filter paper and provided corresponding supplements. Previous studies have shown that workers of R. chinensis are able to develop into neotenics (supplementary reproductive) when the primary queen dies or is lost (Su et al, 2015). Here, in our observations, after about three weeks, the workers will be differentiated into neotenics.…”

High numbers of unrelated reproductives in the Australian ‘higher’ termite Nasutitermes exitiosus (Blattodea: Termitidae)

“…N. nigriceps populations have been found to be ~ 95% simple families and ~ 5% extended families (Thompson and Hebert 1998). Adultoid reproductives, alates that shed their wings and become secondary reproductives (Su et al 2015), have been found in N. principes (Roisin and Pasteels 1986).…”

“…N. nigriceps populations have been found to be ~ 95% simple families and ~ 5% extended families (Thompson and Hebert 1998). Adultoid reproductives, alates that shed their wings and become secondary reproductives (Su et al 2015), have been found in N. princeps (Roisin and Pasteels 1986). N. exitiosus colonies may contain the highest number of primary, unrelated queens in a single colony known from any higher termite species.…”