Fig. 6
Musculoskeletal ovipositor system of Lariophagus distinguendus. Segmented 3D model based on SR–µCT data (perspective view; only the left side of the paired ovipositor elements are depicted; cf. Additional file 4). a Orientation of the ovipositor within the metasoma (lateral view, left is anterior; the metasoma is semi-transparent). b–e Cuticular elements, articulations and muscles of the ovipositor (b lateral view, left is anterior; c dorsal view, left is posterior, positions of sections in Fig. 4a–d are indicated here; d medial view, left is posterior; e frontal view). The ovipositor consists of the following cuticular structures (b): 1st valvifer, 1st valvula, 2nd valvifer, 2nd valvula, 3rd valvula and female T9 (9th abdominal tergum). The 1st valvifer is articulated with the 2nd valvifer and the female T9 via the intervalvifer and the tergo-valvifer articulation, respectively (b). It is continuous with the dorsal ramus of the 1st valvula (c). The 1st and 2nd valvulae form the terebra (1st and 2nd valvulae are not distinguished here). The various ovipositor movements are actuated by a set of nine muscles (d): 1st valvifer-genital membrane muscle, dorsal 2nd valvifer-venom gland reservoir muscle, ventral 2nd valvifer-venom gland reservoir muscle part a/b, anterior 2nd valvifer-2nd valvula muscle, posterior 2nd valvifer-2nd valvula muscle, dorsal T9-2nd valvifer muscle part a/b, ventral T9-2nd valvifer muscle, posterior T9-2nd valvifer muscle and T9-genital membrane muscle. f Anterior part of the ovipositor (dorsomedial view, left is posterior) highlighting the basal articulation and the three muscles connected to the venom gland reservoir. g Base of the terebra featuring the laterally placed bulbs, the laminated bridge and the insertion sites of the anterior and posterior 2nd valvifer-2nd valvula-muscles (i.e. the processus articularis and the processus musculares, respectively) and their orientation (left is anterior; g lateral view, h dorsal view). i Ventral part of the 1st valvifer (posterior view) highlighting the bifurcated posteroventral corner forming one part of the intervalvifer articulation, and the horizontal ridge that is part of the tergo-valvifer articulation. j 1st valvifer (lateral view, left is anterior) with dorsal ramus of the 1st valvula. Acting muscle forces are visualized by solid red arrows. Under the simplified assumption that the 2nd valvifer, which acts as the frame of reference, and the female T9 are guided and cannot twist but only slide towards or against each other along the anterior–posterior axis, the input force vectors Fm-d-T9-2vf(x)-in and Fm-v-T9-2vf(x)-in act in the same plane only at the tergo-valvifer articulation. The distance between the tergo-valvifer articulation (where the force is applied) and the intervalvifer articulation (pivot point/joint axis) is the anatomical inlever a, the effective (= mechanical) inlever is a'; for torques, see equations (eqs.) 1, 2. The 1st valvifer acts as a lever with the anatomical outlever b being the distance between the intervalvifer articulation and the point at which the 1st valvifer continues as dorsal ramus of the 1st valvula, the effective outlever is b', resulting in pro- or retraction forces at the dorsal ramus of the 1st valvula Fm-d-T9-2vf-out and Fm-v-T9-2vf-out; see eqs. 3, 4. Abbreviations: 1vf: 1st valvifer; 1vv: 1st valvula; 2vf: 2nd valvifer; 2vv: 2nd valvula; 3vv: 3rd valvula; ba: Basal articulation; blb: Bulb; dr1: Dorsal ramus of the 1st valvula; F: Force; F(x): Horizontal vector component of a force; iar: Interarticular ridge of the 1st valvifer; iva: Intervalvifer articulation; lb: Laminated bridge; m-1vf-gm: 1st valvifer-genital membrane muscle; m-a-2vf-2vv: Anterior 2nd valvifer-2nd valvula muscle; m-d-2vf-vr: Dorsal 2nd valvifer-venom gland reservoir muscle; m-d-T9-2vf-a: Dorsal T9-2nd valvifer muscle part a; m-d-T9-2vf-b: Dorsal T9-2nd valvifer muscle part b; m-p-2vf-2vv: Posterior 2nd valvifer-2nd valvula muscle; m-p-T9-2vf: Posterior T9-2nd valvifer muscle; m-T9-gm: T9-genital membrane muscle; m-v-2vf-vr-a: Ventral 2nd valvifer-venom gland reservoir muscle part a; m-v-2vf-vr-b: Ventral 2nd valvifer-venom gland reservoir muscle part b; m-v-T9-2vf: Ventral T9-2nd valvifer muscle; mb2: Median bridge of the 2nd valvifers; me: Metasoma; mr2: Medial ridge of the 2nd valvifer; prf: Post-ramus flap; T9: Female T9 (9th abdominal tergum): tva: Tergo-valvifer articulation; trb: Terebra