黄脊雷蓖蝗越冬卵的滞育发育特性

Abstract

黄脊雷蓖蝗<em>Rammeacris kiangsu</em> Tsai是我国竹林的重要害虫,1年发生1代,以卵越冬。为弄清其卵滞育发育特性,调查了卵期温度及低温处理对其卵孵化的影响,检测了恒温条件下胚胎的发育进度及卵粒含水量、过冷却点的变化。结果表明,在不同的卵期温度条件下黄脊雷蓖蝗卵的孵化前期均较长,且孵化不整齐、孵化期间长;低温处理30、60或90 d可显著促进其卵的孵化,低温处理的时间越长效果越明显。说明黄脊雷蓖蝗的卵存在滞育现象,低温能明显降低其卵滞育强度。胚胎头幅、触角长度及体长的测量结果显示, 25 ℃温度条件下的黄脊雷蓖蝗的胚胎发育可划分为3个阶段,即前期的持续发育阶段、中期的发育延迟阶段和后期的发育恢复阶段。产卵后40 d左右卵进入滞育,40-75 d为卵的深度滞育期。黄脊雷蓖蝗的卵粒产下后水分含量较低,在25 ℃的温度条件下,于产卵后25 d前后有一快速的吸水过程,其后卵粒的含水量增加缓慢,可见其卵粒的吸水发生在进入滞育状态之前。在25 ℃的条件下,黄脊雷蓖蝗卵粒过冷却点的变化亦包含3个阶段,即胚胎发育初期的较高阶段、中期持续而稳定的较低阶段及后期的提升阶段,可以认为黄脊雷蓖蝗越冬卵耐寒性的提高与其滞育的发生密切相关。;The bamboo grasshopper, <em>Rammeacris kiangsu</em> Tsai (Orthoptera: Arcypteridae), is an important pest attacking various species of bamboos including <em>Phyllostachys pubescens </em>and <em>Bambusa textilis. </em>It is widely distributed in many provinces of China, including Jiangshu, Zhejiang, Anhui, Sichuan, Hubei, Hunan, Fujian, Guangdong and several others. It is known to be univoltine across its range of distribution and overwinters as eggs. In this article, we investigated the characteristics of its diapause development, including effects of constant temperatures and low-temperature treatments on egg hatching, and embryonic development, water content, supercooling point of the eggs. The results showed that the species has a prolonged pre-hatching period of eggs and an irregular hatching under different constant temperatures. Chilling at 8 ℃ for 30, 60, or 90 days had an increasingly evident effect promoting egg development, resulting in increasingly shorter pre-hatching period of eggs. These results indicated that egg diapause occurred in<em> R. kiangsu</em> and low temperature could decrease the intensity of diapause. When egg pods produced by adults reared in wood-framed cages at 25℃ and LD 16: 8 h in a greenhouse were incubated at 25℃, the embryos showed continuous development, as measured by embryonic head width, antennae and body length, within the first 40 days, followed by a period of obvious developmental stagnation, and resumed from about day 80 after deposition. The results suggested that the embryonic development<em> R. kiangsu</em> could be divided into three stages, <em>i.e</em>. pre-diapause developmental stage, diapause stage and post-diapause developmental stage under 25℃. Eggs entered diapause about 40 days after deposition and reached a deep-diapause stage from 40 to 75 days. The eggs had very low water content immediately after spawning, experienced a quick water absorption period about 25 days after deposition, and showed no obvious water content increase subsequently, indicating water absorption of eggs takes place before diapause. The supercooling point varied depending on the developmental stages of the eggs, being about -20℃ in pre-diapause developmental stage, decreasing remarkably in diapause stage, and resuming in post-diapause stage, suggesting that cold tolerance of overwintering eggs was closely related to diapause in<em> R. kiangsu</em>.