Do northern populations of Reticulitermes speratus (Kolbe) possess an additional physiological capacity to cold-acclimate that enhances cold tolerance during the winter?

Abstract

We measured and compared different carbohydrates, the total lipids, and the body water content between summer- and winter-acclimatized Reticulitermes speratus (Kolbe) in three latitudinal regions to determine whether northern populations possess an additional physiological capacity to acclimate to cold temperatures.The results of supercooling points and the lower lethal temperatures of summer- and winter-acclimatized R. speratus workers revealed that these termites are adapted to cold climates by altering their carbohydrate metabolites (e.g., glucose and trehalose), and balanced their body water content and total lipids to improve their survivability by adapting the physiological strategies to tolerate inclement environment conditions. We observed a mean SCP of −5.1°C for summer-acclimatized R. speratus, which is below the observed mean lower lethal temperature; their SCP slight increase to −6.9°C with winter-acclimatized R. speratus. Within three contrasting locations, R. speratus populations in Kyoto had higher levels of carbohydrate metabolites alteration, lower supercooling points, and lower lethal temperatures. The results of this study support the null hypothesis that termite adapted the physiological strategies to tolerate cold environment. However, the geographical range of R. speratus is not necessarily dependent on only its physiological strategies. Instead, we conclude that it appears to rely on a combination of behavioral, physiological, and other competitive adaptations that ensure the survival of the whole colony under low, non-optimal temperatures. Additionally, the northern populations of R. speratus do not possess an additional physiological capacity to cold-acclimate that enhances cold tolerance during the winter.