The dynamics of super-cooling ability and biochemical substances in the overwintering Carposina niponensi Walsingham(Lepidoptera: Carposinidae) larvae

The peach fruit moth,Carposina niponensis Walsingham,is one of the key insect pests on fruit trees,such as apple,peach and hawkthorn.Its damages have been growing up in recent years because of the effects of fruit cultivation model,the adjustment of planting structure and global warming.Under natural conditions the moth develops one to two generations in Shandong province and overwinters as cocooned larvae for nearly eight months in the upper layer of soil.In the present study,experiments were carried out to examine the larval super-cooling capacity,the content of water,fat,protein and glycogen in the body during the overwintering period.Results showed that the super-cooling ability of larvae was gradually strengthened with the dropping of winter temperature,and weakened with the increasing of the temperature after winter.The super-cooling point(SCP) and freezing point(FP) of the larvae in March dropped to the lowest,-14.89℃ and-9.95℃,respectively,significantly lower than those in other months,while there was no significant difference between the pre-and late-overwintering months.The dynamics of water,protein and glycogen content in the body were similar to that of SCP although they had their own characters during overwintering.The content of water,protein and glycogen reached to the lowest in February,44.83%,32.44μg/mg and 1.95μg/mg,respectively.The fat content in the body decreased from 29.04% in October to 15.56% in June during the overwintering.The fat and glycogen content in pre-overwintering months were remarkably higher than those in mid-and late-overwintering months.Though there is no statistically significant correlation between the larval SCP and the content of total fat,total protein,glycogen or water in the body,their similar changing trends during the overwintering still indicate a quite close relationship between the larval SCP and the total content of the three biochemical substances or water content.Our study reflects that the overwintering larvae of C.niponensi can adjust their behavior and physiology so as to adapt to disadvantageous conditions in winter.The dynamic variation of the larval super-cooling ability is influenced by the dynamic variation of the content of biochemical substances in the body during overwintering.As a result the larvae make ecological adaptation to the stress of low temperature in winter.