Abstract
The Chinese pine caterpillar Dendrolimus tabulaeformis is an important destructive leaf borer in boreal coniferous forests in China. This species overwinters in the larval stage. Changes in supercooling capacity and physiological-biochemical parameters of D. tabulaeformis larvae from a natural population were evaluated at different stages during the overwintering period. Cold hardiness of overwintering larvae collected in January was significantly greater than that of larvae collected in other months. January larvae survived for 15 days at -10°C and for approximately 2 days at -15°C. By contrast, larvae collected in September survived for no more than 4 h at -5°C and those in November and March no more than 1 day at -15°C. Supercooling point gradually decreased from -5.9 ± 0.3°C in September to a minimum of -14.1 ± 1.0°C in November, then gradually increased to the original value with the advent of spring. Water content gradually decreased from September to November, remained at approximately 74.5% until March and then gradually increased to levels similar to those in September. The lipid content gradually decreased from September to November, remained stable at approximately 3.2% until March and then gradually increased to levels similar to those in September. Glycogen content increased to a peak in November and then decreased. The concentrations of several metabolites showed significant seasonal changes. The most prominent metabolite was trehalose with a seasonal maximum in November. Glucose levels were highest in January and then gradually decreased until in May they were at levels similar to those in September. Glycerol levels remained relatively stable during winter but increased significantly in May. This study indicates that D. tabulaeformis is a freeze-avoidant insect. Larvae increase their supercooling capacity by regulating physiological-biochemical parameters during overwintering. Our results provide the basis for further research into the mechanism of cold hardiness in this species.
Highlights
All stages of an insect’s life cycle are affected by temperature
The percentage survival decreased to 70.0% after 1 day of exposure to –10°C, and larvae could not survive at temperatures below –15°C
Our results indicate that the low temperatures experienced while overwintering enhance the cold hardiness of D. tabulaeformis larvae
Summary
All stages of an insect’s life cycle are affected by temperature. Low temperature is a key factor in insect growth and development and can impose strict limits on insect populations (Jing & Kang, 2002; Wang & Kang, 2014). Insects can adjust physiological-biochemical parameters to increase their supercooling capacity, enhancing their cold hardiness (Lee, 1989; Storey & Storey, 1991). Survival at low temperatures is a good indicator of cold hardiness, which is thought to be closely related to the supercooling point (SCP) of a species, which is the lower temperature at which it dies (Lee & Denlinger, 1985; Hao & Kang, 2004; Jing & Kang, 2004). The supercooling point is an important indicator of the cold hardiness and overwintering strategy of an insect (Bale, 1996; Jing & Kang, 2002; Feng et al, 2016). Previous research indicates that insect cold hardiness is closely connected with changes in many parameters such as water, lipid and glycogen content (Bale, 2002; Wang et al, 2011; Feng et al, 2015). Many cold-hardy insects produce and accumulate low molecular weight metabolites to increase their supercooling capac-
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
