Physiological profiles associated with ceasing growth of unfertilized eggs produced by unmated queens in the subterranean termite Reticulitermes chinensis.

Ganghua Li,Pengdong Sun,Yao Wu,Qiuying Huang,Xiongwen Chen,Chaoliang Lei,Long Liu

doi:10.1242/bio.017319

Ganghua Li, Pengdong Sun + Show 5 more

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https://doi.org/10.1242/bio.017319

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Abstract

ABSTRACTIn Reticulitermes chinensis, a close relative of R. speratus with asexual queen succession, unfertilized eggs can be produced but do not hatch as larvae. To explain this phenomenon, we analyzed the physiological differences between unfertilized eggs/unmated queens and fertilized eggs/mated queens. Fertilized eggs had significantly lower quantities of five amino acids (Cys, Met, Ile, Leu and Tyr), Ca, protein and cholesterol during development. The higher levels of four trace elements (Na, K, Zn and Fe) in fertilized eggs and their lower levels in mated queens indicated that mated queens might transfer these trace elements to fertilized eggs to aid development. The higher levels of Mn, triglycerides and serotonin in mated queens and higher levels of Mn and glucose in fertilized eggs suggested that these substances are very important for normal ovarian and embryonic growth. The different expression of three reproductive genes (vtg 1, rab 11 and JHE 1) suggested that they might be involved in the regulation of ovarian and embryonic growth. Overall, changes in these physiological indices may substantially affect ovarian and embryonic growth and inhibit development of unfertilized eggs in R. chinensis.

Highlights

Asexual queen succession (AQS) has been described in three species of lower termites [Reticulitermes speratus (Matsuura et al, 2009), R. virginicus (Vargo et al, 2012) and R. lucifugus (Luchetti et al, 2013)] and two species of higher termites [Embiratermes neotenicus (Fougeyrollas et al, 2015) and Cavitermes tuberosus (Roisin et al, 2014)]
Some termite species that are evolutionally related to asexual queen succession (AQS) species of termites have been demonstrated to exhibit neither AQS nor parthenogenesis (Kawatsu and Matsuura, 2013; Luchetti et al, 2013); little is known about why these termite species have no AQS and why unfertilized eggs produced by unmated queens of these species are unable to hatch
We found that unfertilized eggs ceased embryonic growth and had significant differences in morphological characters, size and micropyle number compared with fertilized eggs in the final stage of development

Summary

Introduction

Asexual queen succession (AQS) has been described in three species of lower termites [Reticulitermes speratus (Matsuura et al, 2009), R. virginicus (Vargo et al, 2012) and R. lucifugus (Luchetti et al, 2013)] and two species of higher termites [Embiratermes neotenicus (Fougeyrollas et al, 2015) and Cavitermes tuberosus (Roisin et al, 2014)]. In AQS species of termites, workers, soldiers and alates are sexually produced but neotenic queens arise through thelytokous parthenogenesis (Matsuura et al, 2009). This AQS system enables the primary queen to maintain her full genetic contribution to the generation while avoiding any loss of genetic diversity from inbreeding (Matsuura, 2011). Some termite species that are evolutionally related to AQS species of termites have been demonstrated to exhibit neither AQS nor parthenogenesis (Kawatsu and Matsuura, 2013; Luchetti et al, 2013); little is known about why these termite species have no AQS and why unfertilized eggs produced by unmated queens of these species are unable to hatch

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