Effects Of Low Temperature 20℃ On The Egg And Embryonic Development Of Honeybee(Apis Mellifera Ligustica)

Honeybee is a model organism for eusocialism,as well as an economic insect for pollination and bee products yield.The honeybee brood adapted to a stenothermal nest temperature and could be susceptible to abnormal ranged temperature stress.The low temperature effects on honey bee Apis mellifera ligustica(Spinola)eggs and embryo development remain unknown.The hatchablity and development duration were compared between various aged un-and fertilized eggs subjected to 20℃ for a hierarchy of hours(0.5、1.0、2.0、4.0、8.0、12.0、16.0、20.0、24.0、28.0、32.0、36.0 h)to assess the negative effects.The embryonic tissues were studied in order to address the cold temperature effects of low temperatue on the early development of the honeybee worker embryo development.The results are as follows:(1)Effects of low temperature stress of Apis mellifera ligustica eggsThe hatchability and development duration of eggs were significantly affected by the cold exposure.Both un-and fertilized eggs aged 0-9 h showed a worst cold susceptibility and none survived to hatching when 20℃ exposed for more than 4.0 h.On the contrast,eggs of 12-24 h and eggs of aged>36 h showed no negative effect at 4.0 h and 12.0 h,respectively,but both groups deceased hatchability as cold exposure time prolonged.The increased hatching duration of eggs(aged>12 h)were highly correlated to the cold exposure duration,namely,the prolonged hatching duration value was approximately equal to the cold exposure time.Both the un-and fertilized eggs(aged>12 h)of honeybee are susceptible to cold,and their sensitivity susceptiblity depends on the egg age after laid and cold exposure duration interaction.Basically,the both un-and fertilized eggs of 0-9 h are most susceptible to cold,followd by eggs of 12-24 h,and eggs aged>36 h.(2)Effects of low temperature on the embryo devel opment of Apis mellifera ligusticaHoneybee Apis mellifera ligustica worker embryo aged 12 h were exposed to 20℃ for 1.0、2.0、4.0、6.0、8.0、12.0 h showed development suspension there and no change occurred under cold stress.The recovery of development took place in cold stressed embryos but showed delayed development process when they were brought back to 35℃.The embryos aged 12 h at its syncytium were stressed at 20℃ for 8.0 h and recovered at 35℃ for hours,no development recovery could be detected during the first 1-2 h recovery,but nuclei dispersed into periplasm after 4.0-6.0 h recovery without cell membrane which began to form until recovery for 8.0 h.When recovered for 24.0 h,embryos entered into germ layer formation and formed bilayer blastderm which formed at 36 h old after eggs laying at 35℃.When recovered for 48.0 h the stressed embryos entered into organismal formation of larval foregut and midgut as those of 60 h at 35℃.Our data suggested the early embryo were most susceptiblae to cold stress which implies aved the way for future mechanism underlying the honeybee embryos vulnerable to cold,and provided scientific insights for novel beekeeping strategies.