Abstract
BackgroundGenerally in termites, alates differentiate through multiple nymphal instars which gradually develop wing buds. However, in a dampwood termite, Hodotermopsis sjostedti, alates molt directly from a single nymphal instar with short wing buds. In this study, to examine the mechanism underlying the wing formation during the alate differentiation in H. sjostedti, histological and morphological observations were carried out on the developmental process of wing formation during the nymphal instar, in comparison with those in Zootermopsis nevadensis, which has two nymphal instars. Furthermore, the expression patterns of genes that are thought to be responsible for wing formation, i.e., wing-patterning genes and genes encoding hormone-related factors, were quantified during alate differentiation and compared between the two species.ResultsThe results showed that, in H. sjostedti, wings were formed in a complicatedly folded shape, not only inside the wing buds as seen in Z. nevadensis, but also under the dorsal thoracic cuticle, where the wing tips shifted toward the median thoracic part. Accordingly, the wing expansion pattern also differed from that in Z. nevadensis. Furthermore, the results of real-time qRT-PCR on overall expression profiles of wing-patterning genes and hormone-related genes suggest that the single nymphal instar in H. sjostedti well resembles to the second nymphal instar in Z. nevadensis. In particular, significant upregulation of vestigial (vg) and downregulation of Krüppel homolog 1 (Kr-h1) that were observed at the second nymphal instar in Z. nevadensis apparently occurred during the single nymphal instar in H. sjostedti.ConclusionThe developmental events for wing formation are compacted into a single nymphal instar in H. sjostedti, and as a result, the unique wing formation is seen to compensate for the spatial restriction inside small wing buds, leading to the completion of functional wings.
Highlights
In termites, alates differentiate through multiple nymphal instars which gradually develop wing buds
Histological observations during wing formation Based on histological observations on paraffin sections of thoracic parts of nymphs, the developmental patterns of wings inside wing buds were compared between H. sjostedti and Z. nevadensis (Fig. 2)
This study revealed that many of the genes required for wing formation are upregulated in the second nymphal instar of Z. nevadensis, but in the first nymphal instar of H. sjostedti (Figs. 4, 5)
Summary
Alates differentiate through multiple nymphal instars which gradually develop wing buds. The expression patterns of genes that are thought to be responsible for wing formation, i.e., wing-patterning genes and genes encoding hormone-related factors, were quantified during alate differentiation and compared between the two species. Eusocial insects such as bees, wasps, ants and termites show highly organized sociality with divisions of labor among morphologically and behaviorally differentiated castes [1]. In the linear pathways, all individuals go through larval instars without wing buds up to late instars (i.e., pseudergates that perform worker tasks but still possess potential to develop into alates). The forked pathways are seen in Mastotermitidae, Hodotermitidae, and most species of Rhinotermitidae and Termitidae, while the linear pathways are seen in Archotermopsidae, Kalotermitidae, Serritermitidae and a part of Rhinotermitidae [3, 8]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
