| As the main hazard species in the mountain steppe,Aeropus sibiricus is widely distributed and abundant.Its eggs overwinter in the soil,and the overwintering rate and hatching rate of eggs directly affect the occurrence amount in the following year.Therefore,the study of the morphological characteristics and cold tolerance of the eggs of Aeropus sibiricus provides an important theoretical basis for the analysis of the distribution and population dynamics of Aeropus sibiricus,forecast and prevention and control.In order to study the external morphological characteristics and the cold tolerance of eggs,the morphological characteristics of eggs、hoppers、adults,the male genitalia,the forewing veins,the developmental period and the cold tolerance of eggs of Aeropus sibiricus were systematically studied in this paper.The main results are as follows:1.Morphological characteristics of A.sibiricus eggs、hoppers、adultsThe egg is straight or slightly curved,thicker in the middle,tapering towards both ends,blunt at the upper end,narrow at the lower end,grayish white,with a length-width ratio of about 2.9.The shape of the oocysts is straight or slightly curved,with a length to width ratio of about 2.1.A total of4 instars developed into adults.The egg sac contains 5～10eggs.The body color of the 1st instar hoppers is light yellow at the beginning of hatching,and then gradually turns dark brown,the body color of 4th instar nymph and adult appears light green.The pronotum posterior of the 1st and 2nd instars nymph is almost straight,the 3rd instar nymph begins to bend,and the adult are curved.The 1st and 2nd instar nymph’ wing buds are not obvious,but gradually obvious from the 3rd,the front wing turns back when the adult,the male’s front wing is 1～2mm larger than the abdomen,while the female’s front wing is less than the abdomen.The lateral keels at the beginning of the 2nd instar nymph,apex of antennae began to expand gradually,top of male antennae slightly bends inward when adult.Both the propodium tibia and pronotum in nymph of A.sibiricus were not swollen,during the last molt before they become adults,the propodium tibia and pronotum of males were found to be swollen.2.Description of male external genitalia and forewing veins of A.sibiricusThe epiphallus in A.sibiricus presents bridge shape,with arched bridge.The top of ancorae(An)is sharp and slightly curved inward.The upward protrusion of anterior pro(Ant)is triangular,and the posterior projection(Pp)has outward acute angle protrusion.The lophi(L)is divided into inner and outer lophi,the inner lophi is kidney shaped and the outer lophi is oval.The basal valves of penis(Bp)in phallic complex of A.sibiricus have been found in two pieces,which are presented in petal shape with sharp angular protrusions at the tip.Zygoma(Zy)is U shaped and reaches 1/2 of the basal valves of penis.The base of valves of cingulum(Vc)has a relatively-wide inverted U-shaped notch.The apical valves of penis(Ap)present sharp-spine shape,which are curved in the direction of zygoma with hook shape and divided into two valves respectively.The fore wings of A.sibiricus exceeded the end of meropodium of metapedes.The anterior cubitus(Cu A)and posterior cubitus(Cu P)were partially or completely merged with each other.At the same time,the detailed indexes of each part of male external genitalia were measured.3.Development period of A.sibiricusThe developmental duration of each stage of hoppers in A.sibiricus is11～13 days for the first instar,8～10 days for the second instar,6～8 days for the third instar,7～13 days for the fourth instar,6～24 days for the male adult,11～43 days for the female adult,the total developmental duration of eclosion adults is 40～87 days.4.Effect of low temperature acclimation on supercooling points of A. sibiricus eggsThe supercooling points of non acclimated eggs is-26.41±1.0℃.The supercooling points of eggs acclimated at 10℃,5℃,0℃,-5℃ and-10℃for 7 days are respectively-26.60±0.79℃、-27.44±1.36℃、-26.81±0.65℃、-27.93±1.30℃、-27.92±1.02℃.The supercooling points of acclimated eggs is significantly lower than that of non acclimated eggs after low temperature acclimation below 0℃.The supercooling points of A.sibiricus eggs decreases with the decrease of domestication temperature.5.Effect of low temperature acclimation on free water content of A.sibiricus eggsThe content of free water in non acclimated eggs is 55.72±0.98%,The content of free water of eggs acclimated at 10℃,5℃,0℃,-5℃ and-10℃for 7 days are respectively 53.76±0.80%、55.15±1.34%、53.88±0.97%、52.98±1.00%、52.68±1.32%.The free water content of acclimated eggs was significantly lower than that of unacclimated eggs at other temperatures except 5℃(P<0.05).The content of free water in eggs decreased with the decrease of acclimation temperature.The trend of supercooling point and free water content in the body is similar.6.Effect of low temperature acclimation on glycogen content of A.sibiricus eggsThe content of glycogen in non acclimated eggs is 0.078±0.018 μg/mg,the content of glycogen of eggs acclimated at 10℃,5℃,0℃,-5℃ and-10℃for 7 days are respectively 0.040±0.006 μg/mg 、 0.081±0.003 μg/mg 、0.090±0.002 μg/mg、0.108±0.010 μg/mg、0.087±0.022 μg/mg.Although the glycogen content of acclimated eggs was not significantly different from that of unacclimated eggs,the glycogen content of acclimated eggs was higher than that of unacclimated eggs except acclimated eggs at 10℃.The glycogen content firstly decreased,then increased and then decreased. |
