Abstract
In cooperative societies such as those of ants, honey bees, and termites, the number of reproductives is often regulated by social interactions. In many termite species, helper individuals (i.e., larvae or workers) can potentially differentiate into a “neotenic” reproductive caste in the absence of reproductives. In some termite species, multiple neotenics coexist within a nest, often with female-biased sex ratios. However, although the presence of female neotenics can suppress neotenic differentiation of female workers, it is largely unknown how male neotenics affect the differentiation of female neotenics. Here, we show that male and female neotenics regulate the neotenic differentiation in a sex-specific manner in the damp-wood termite Hodotermopsis sjostedti, whose colonies are often headed by multiple male and female neotenics in the field. Our rearing experiments showed that the presence of female neotenics suppressed differentiation of female neotenics from fourth- to seventh-larvae, i.e., pseudergates (called as “workers” in this study), whereas male neotenics promoted the differentiation of female neotenics. Moreover, the results of rearing experiments that restricted physical contact between neotenics and workers suggested that these effects were not mediated by volatile chemicals, but rather by direct contact. We found that the male neotenics were frequently groomed by female workers, suggesting that these interactions promote the differentiation of female neotenics. Our results represent an empirical evidence that the neotenic differentiation from female and male workers is regulated by direct physical contact with the preexisting neotenics.
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Acknowledgements
We thank Osamu Kitade in Ibaraki University for valuable discussions and sharing his field data; Masahiro Shimizu for assistance with the experimental setup; and Dai Watanabe, Yasuhiro Sugime, and Run Minoura for collecting termites and maintenance of stock colonies. This work was supported by a Grant-in-Aid from the Japan Society for the Promotion of Science Fellows (no. 13J04279 to HS) and a Grant-in-Aid for Scientific Research A (no. 25251041 to TM) from the Ministry of Education, Culture, Sports, Science and Technology of Japan.
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Hiroyuki Shimoji, Kohei Oguchi and Yoshinobu Hayashi contributed equally to this research.
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Shimoji, H., Oguchi, K., Hayashi, Y. et al. Regulation of neotenic differentiation through direct physical contact in the damp-wood termite Hodotermopsis sjostedti . Insect. Soc. 64, 393–401 (2017). https://doi.org/10.1007/s00040-017-0562-y
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DOI: https://doi.org/10.1007/s00040-017-0562-y