云南切梢小蠹雌成虫卵巢发育程度的分级研究

Processing-morphology Change and Grading Criteria for Ovarian Development in Tomicus yunnanensis (Coleoptera, Scolytidae)

[目的]探究卵巢发育与环境温度在云南切梢小蠹生殖和种群繁衍中的作用,进而加深对其种群数量动态和成灾机制的认识。[方法]采用随机抽样法,于2014年12月—2016年1月解剖正在云南松枝梢内取食的云南切梢小蠹雌成虫。[结果]云南切梢小蠹雌成虫卵巢位于第4腹节消化道侧下方,由1对卵巢、2根短侧输卵管、1根中输卵管、受精囊和附腺构成;卵巢包括四根管状的卵巢管,每个卵巢管前端延伸出端丝并集合成悬带,附着于体壁或脂肪体上。根据卵巢发育形态特征的变化,分为透明期(I级)、延伸期(Ⅱ级)、卵黄沉积前期(Ⅲ级)、卵黄沉积期(Ⅳ级)、产卵期(Ⅴ级)共5个等级,卵巢发育过程与蛀梢补充营养密切相关,每一级别可持续1～4月不等; I-Ⅳ级卵巢管长度增长较慢,Ⅴ级增长快速,而卵巢管宽度Ⅱ级和Ⅴ级增加快,卵巢面积呈幂指数级增长。结合环境温度和林间蛀干调查,发现云南切梢小蠹卵巢发育与温度呈正相关,而蛀干产卵与温度负相关。[结论]云南切梢小蠹雌成虫卵巢发育主要集中在Ⅲ～Ⅴ级,且温度影响该蠹虫的蛀梢和蛀干产卵,研究可为云南切梢小蠹产卵期的预测预报提供理论依据。

[Objective] To investigate the role of ovarian development associated with environmental temperature in reproduction and population growth of Yunnan shoot borer Tomicus yunnanensis for further understanding the basic mechanism of its population fluctuation. [Method] The females of T. yunnanensis were randomly obtained from the shoot of Pinus yunnanensis, and dissected on a paraffin plate. [Result] The female reproductive system of Yunnan shoot borer is located in the inferior toward the lateral part of alimentary canal at the fourth abdominal segment. It consists of a pair of ovaries and two short lateral oviducts, a common oviduct, a spermatheca and two accessory glands. The ovaries have four tubular ovarioles. The terminal filaments extended from the anterior end of each ovariole can adhere to the internal tegument or fat body. According the morphological changes, the ovarian development was divided into five grades, including transparent period(grade Ⅰ), terminal elongation period(grade Ⅱ), previtellogenic(Ⅲ grade), vitellogenic eggs(grade Ⅵ), and ovipositing period(grade Ⅴ). Each grade of ovarian development can last less than 1 to 4 month, and show a closely relation to the nutrient acquisition. The length of ovariole grows slowly in the previous and middle and rapidly in late grades, but the width of ovariole grow rapidly in the previous and late grades. The whole size of ovary increase rapidly with a power-law dependence. Using Kendall’s tau-b correlation analysis, it was found that the correlation between ovarian development and temperature was positive, and a negative relationship was found between oviposition and temperature. [Conclusion] The ovarian devel-opment of female adults of T. yunnanensis focuses mainly on the middle and late grades. The environment temperature has a significant effect on the life style of shoot and stem, respectively. The results can help to further deepening the theoretical basis for the prediction of oviposition of Yunnan shoot borers.