Effect of long-term cold storage on trehalose metabolism of pre-wintering Harmonia axyridis adults and changes in morphological diversity before and after wintering

Abstract

Harmonia axyridis is a major bio-control agent of pests in agriculture and forest ecosystems. It is also a globally important invasive insect species. To test whether dark elytra colour is associated with greater cold hardiness, we compared the survival rate of prolonged cold exposure in both yellow and black colour morphs of female and male H. axyridis. We determined the trehalose and glycogen content, trehalase activity, and the dynamics of genes associated with the trehalose metabolic pathway. Yellow forms predominated before winter began, however black forms increased from 11.15 to 30.46% after overwintering. There was no significant difference in trehalose content between the females and males during overwintering. Glycogen content in over-wintering yellow females and black males increased significantly, while it decreased in black females. Soluble trehalase activity increased significantly in all the insects except black females. Membrane-bound trehalase activity increased in black males, and decreased in black females. Trehalose and glycogen content and trehalase activity were regulated by differential expression of TRE and TPS genes. Female beetles weighed more than males and survived in low temperatures for longer periods of time, regardless of elytra colour, suggesting that mass is a stronger predictor of overwintering survival rather than colour morph. Our results provide a guide for comparing cold resistance in insects and a theoretical basis for cold storage of H. axyridis for use as natural enemies of pests in biological control programs.

Cold Storage of Predatory Coccinellid Coccinella septempunctata L. (Coleoptera; Coccinellidae) to Increase its Shelf-Life for Biological Control Programmes

“…Likewise, the present study showed that C. septempunctata adult and larvae could be stored for short term without any severe impact on their development or afterward survival. Such flexibility for tolerating low temperature conditions can be helpful in different mass rearing techniques of beneficial coccinellids (Zeng et al, 2020). In C. septempunctata diapause is a conspicuous feature and beetles pass through facultative diapause even under suitable environmental conditions when feeding regime is changed (Suleman, 2015).…”

“…As the storage duration increased, the survival of the beetles (days) was reduced after removal from cold storage conditions. However, intensity of these negative effects on the biotic parameters of insects under storage is mostly proportional to the period of low temperature (Zeng et al, 2020). Therefore, people involved in the bulk production of these beneficial insects may have the choice to keep particular species in cold storage for length of period till it meets the basic requirements.…”

Lethal and Sublethal Effects of Long-term Cold Storage on Indoor-reared Harmonia Axyridis Adults

“…The multicolored Asian ladybird beetle, Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae), native to Asia, has established populations worldwide and has also been considered as an important invasive insect species [13][14][15] . At present, this predatory ladybird beetle has been commercially reared and widely used as a biocontrol agent in many agricultural elds 16,17 due to its excellent voracity, dispersal capacity and multivoltine life-cycle 18,19 . However, H. axyridis is a "chill intolerant" predator 20 , and the logistics of low-temperature storage has been shown to be one of the most important limitations in using it in biological control programs 21,22 .…”