Experimental Zoology Group, Wageningen University, 6708 WD Wageningen, The Netherlands.
Zoological Institute: Functional Morphology and Biomechanics, Kiel University, 24118 Kiel, Germany.
J Exp Biol. 2019 May 2;222(Pt 9):jeb195628. doi: 10.1242/jeb.195628.
Many parasitic wasps use slender and steerable ovipositors to lay eggs in hosts hidden in substrates, but it is currently unknown how steering is achieved. The ovipositors generally consist of three longitudinally connected elements, one dorsal and two ventral valves that can slide along each other. For the parasitic wasp , it has been shown that protraction of the ventral valves causes incurving of the ventral valves towards the dorsal one, which results in a change in probing direction. We hypothesize that this shape change is due to differences in bending stiffness along the ovipositor. Alignment of the stiff tip of the dorsal valve with a more flexible ventral S-shaped region situated just behind the tip straightens this S-bend and results in upwards rotation of the ventral tip. We show that the S-shaped region of the ventral valves has a low bending stiffness because it contains soft materials such as resilin. In contrast, the large cross-sectional area of the dorsal valve tip area probably results in a high bending stiffness. Elsewhere, the dorsal valve is less stiff than the ventral valves. Our results support the hypothesis that the interaction between the stiff dorsal valve portion and the more flexible S-shaped region co-determines the configurational tip changes required for steering the ovipositor in any desired direction along curved paths in the substrate. This provides novel insights in the understanding of steering mechanisms of the hymenopteran ovipositor, and for application in man-made probes.
许多寄生蜂利用细长且可操纵的产卵器将卵产在隐藏在基质中的宿主中，但目前尚不清楚如何实现转向。产卵器通常由三个纵向连接的元件组成，一个背侧和两个腹侧瓣，可以相互滑动。对于寄生蜂来说，已经表明腹侧瓣的伸出会导致腹侧瓣向背侧瓣弯曲，从而导致探测方向发生变化。我们假设这种形状变化是由于产卵器沿长度方向的弯曲刚度不同所致。将背侧瓣的坚硬尖端与位于尖端后面的更灵活的 S 形腹侧区域对齐，会使 S 形弯曲变直，并导致腹侧尖端向上旋转。我们表明，腹侧瓣的 S 形区域具有较低的弯曲刚度，因为它包含弹性蛋白等柔软材料。相比之下，背侧瓣尖端区域的大横截面面积可能导致较高的弯曲刚度。在其他地方，背侧瓣比腹侧瓣更柔软。我们的结果支持这样一种假设，即坚硬的背侧瓣部分与更灵活的 S 形区域之间的相互作用共同决定了产卵器在基质中的任何弯曲路径上沿所需方向转向所需的构型尖端变化。这为理解膜翅目产卵器的转向机制提供了新的见解，并为人工探头的应用提供了参考。
