Eggs Benjamin, Fischer Stefan, Csader Michael, Mikó István, Rack Alexander, Betz Oliver
Evolutionary Biology of Invertebrates, Institute of Evolution and Ecology, University of Tübingen, Auf der Morgenstelle 28, 72076, Tübingen, Germany.
Tübingen Structural Microscopy Core Facility (TSM), University of Tübingen, Schnarrenbergstraße 94-96, 72076, Tübingen, Germany.
Front Zool. 2023 Aug 8;20(1):26. doi: 10.1186/s12983-023-00503-1.
Various chalcidoid wasps can actively steer their terebra (= ovipositor shaft) in diverse directions, despite the lack of terebral intrinsic musculature. To investigate the mechanisms of these bending and rotational movements, we combined microscopical and microtomographical techniques, together with videography, to analyse the musculoskeletal ovipositor system of the ectoparasitoid pteromalid wasp Lariophagus distinguendus (Förster, 1841) and the employment of its terebra during oviposition. The ovipositor consists of three pairs of valvulae, two pairs of valvifers and the female T9 (9th abdominal tergum). The paired 1st and the 2nd valvulae are interlocked via the olistheter system, which allows the three parts to slide longitudinally relative to each other, and form the terebra. The various ovipositor movements are actuated by a set of nine paired muscles, three of which (i.e. 1st valvifer-genital membrane muscle, ventral 2nd valvifer-venom gland reservoir muscle, T9-genital membrane muscle) are described here for the first time in chalcidoids. The anterior and posterior 2nd valvifer-2nd valvula muscles are adapted in function. (1) In the active probing position, they enable the wasps to pull the base of each of the longitudinally split and asymmetrically overlapping halves of the 2nd valvula that are fused at the apex dorsally, thus enabling lateral bending of the terebra. Concurrently, the 1st valvulae can be pro- and retracted regardless of this bending. (2) These muscles can also rotate the 2nd valvula and therefore the whole terebra at the basal articulation, allowing bending in various directions. The position of the terebra is anchored at the puncture site in hard substrates (in which drilling is extremely energy- and time-consuming). A freely steerable terebra increases the chance of contacting a potential host within a concealed cavity. The evolution of the ability actively to steer the terebra can be considered a key innovation that has putatively contributed to the acquisition of new hosts to a parasitoid's host range. Such shifts in host exploitation, each followed by rapid radiations, have probably aided the evolutionary success of Chalcidoidea (with more than 500,000 species estimated).
尽管缺少产卵器固有肌肉组织，但各种小蜂科黄蜂仍能将其产卵器管（=产卵器杆）向不同方向灵活转动。为了探究这些弯曲和旋转运动的机制，我们结合了显微镜和显微断层扫描技术以及摄像技术，来分析外寄生性褶翅小蜂科黄蜂Lariophagus distinguendus（Förster，1841）的肌肉骨骼产卵器系统及其在产卵过程中产卵器管的使用情况。产卵器由三对产卵瓣、两对产卵器腹片和雌性第九腹节背板组成。成对的第一和第二产卵瓣通过交合突系统相互联锁，该系统允许这三个部分相对于彼此纵向滑动，并形成产卵器管。各种产卵器运动由一组九对肌肉驱动，其中三对（即第一产卵器腹片-生殖膜肌、第二产卵器腹片腹侧-毒腺储囊肌、第九腹节背板-生殖膜肌）在此首次在小蜂科中被描述。第二产卵器腹片-第二产卵瓣的前后肌肉在功能上有所适应。（1）在主动探测位置，它们使黄蜂能够拉动第二产卵瓣纵向分裂且不对称重叠的两半在背侧顶端融合处的基部，从而使产卵器管发生侧向弯曲。与此同时，无论这种弯曲情况如何，第一产卵瓣都可以伸出和缩回。（2）这些肌肉还可以使第二产卵瓣以及整个产卵器管在基部关节处旋转，从而实现向各个方向的弯曲。产卵器管的位置固定在坚硬基质中的穿刺部位（在其中钻孔极其耗费能量和时间）。一个可自由转动的产卵器管增加了在隐蔽腔体内接触潜在宿主的机会。主动转动产卵器管能力的进化可被视为一项关键创新，据推测这有助于寄生蜂宿主范围获得新的宿主。宿主利用方式的这种转变，每次都伴随着快速的辐射扩散，可能有助于小蜂总科（估计有超过50万种）在进化上取得成功。
