Hypoxia adaptation in termites: hypoxic conditions enhance survival and reproductive activity in royals

Abstract

Termite royals (queen and king) exhibit extraordinary longevity without sacrificing reproductive performance, unlike most animals, in whom lifespan is generally negatively associated with reproduction. Therefore, the regulatory mechanisms underlying longevity have attracted much attention. Although the ageing process is influenced by environmental factors in many insects during their life cycle, it remains unclear whether any factors have an effect on the extended survival and high reproductive capacity of termite royals. Here, we show that hypoxia, possibly an important environmental factor in the nests, enhances survival and reproductive activity in incipient royals of the subterranean termite Reticulitermes speratus compared with those in control conditions. Quantitative real-time PCR analysis revealed that the expression levels of the vitellogenin gene in queens are maintained to a greater extent under hypoxic conditions than under control conditions. The expression levels of the antioxidant enzyme genes RsCAT1 and RsPHGPX are also significantly promoted by hypoxia in queens and kings respectively. These results suggest that hypoxic exposure can contribute in part to achieving high reproductive output by altering gene expression after founding of colonies in the royals. Our study provides novel insights into the effect of a nest environment on the reproductive characteristics in termite royals.

Reproduction deep inside wood: a low O2and high CO2environment promotes egg production by termite queens

“…Lett. 16: 20200049 detecting royal guard soldiers or secondary queens with minimal structural disturbance [20]. Then each log was cut into two or three parts, and a 100-ml gas sample was collected from each part using the downward displacement of water in a 90 l water bath.…”

“…Their nest chambers are formed in decaying wood, where tens of thousands of individuals engage in social labour. Colonies have hidden royal chambers harbouring kings and queens deep inside the wood [18][19][20]. Therefore, the nest gas conditions experienced by Reticulitermes termites, especially in the royal chamber, should be low in O 2 and high in CO 2 compared with ambient gas conditions.…”

Why and how do termite kings and queens live so long?

“…[ [38][39][40][41][42][43] hypoxic nest hypoxic nest could protect the reproductives from oxygen toxicity. [44,45] Physiological characteristics oxidative stress resistance antioxidant system neutralizes the overproduction of reactive oxygen species associated with oxidative stress, which contributes to delayed ageing and long lifespan of the reproductives.…”

“…Hypoxic nests thus may protect reproductives from oxidative stress through interacting with their antioxidant system. Termite reproductives exhibit higher-level reproductive activities, survival and expression of antioxidants and vitellogenin under hypoxia compared to normoxia, suggestive of hypoxic adaptation [44,45]. Intriguingly, during physiological adaptation to hypoxia, the development of anaerobic energyproducing systems operative in the conditions of low oxidative stress may extend the lifespans of termite reproductives.…”

Effects of high CO2 on mating success, mating duration, and sperm transfer in the West Indian sweet potato weevil, Euscepes postfasciatus

“…CO 2 at 25 °C (Delate et al, 1990). However, few investigations have been made into the effects of high CO 2 on behaviour under a realistic range in the habitat (exceptions are Kumar & Saxena, 1978; Tasaki et al, 2018).…”