Contributions to Zoology, 86 (3) – 2017Xin Tong; Lu Jiang; Bao-Zhen Hua: A unique mating pattern of Panorpodes kuandianensis (Mecoptera: Panorpodidae)

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Mating behavior

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Thirteen pairs of P. kuandianensis were recorded to mate in the morning and three of them were frozen in copulation. The male provided a salivary mass to a nearby female and tried to attract her through vibrating his wings rapidly (Fig. 1a). Then he stretched out his paired gonostyli to grasp the abdominal end of the female, used his hypandrium to seize the female cerci and attempted to establish the connection of the genitalia. Meanwhile, the female usually tried to get rid of the male control by wriggling her abdomen. To suppress the female resistance, generally, the male adjusted his posture and seized the female abdomen by the paired basal processes and the basal teeth to couple their genitalia and guarantee the sperm transfer. In the initial phase of copulation, the male randomly stood on one side of the female (six left-sided matings and seven right-sided matings) to sustain a V-shaped position with their genitalia coupled (Fig. 1b). While the female consumed the salivary mass, the male changed the mating position from the V-shape to an end-to-end position (Fig. 1c). The male kept on pulling the female till the end of copulation, and some females (2 of 10) were observed to invert their bodies before terminating copulation (Fig. 1d).


Fig. 1. Mating position of Panorpodes kuandianensis. a, a male is secreting a salivary mass as a nuptial gift; b, initial phase of copulation with the coupling pair sustaining a V-shaped position, arrow points at the salivary mass; c, stable phase of copulation, the coupling pair sustains an end-to-end position with the female abdomen twisted; d, final phase of copulation, the coupling pair sustains an end-to-end position with the female body inverted.

Male and female genitalia

The genital segment (abdominal segment IX, A9) of male P. kuandianensis consists of a dorsal epandrium (tergum IX), a ventral hypandrium (sternum IX), and the median genitalia (Figs 2a, b). The genitalia consist of a central aedeagus, a pair of parameres, and a pair of lateral gonopods (Fig. 2a). The gonopods are fused at the base, each comprising a basal gonocoxite and a distal gonostylus (Figs 2a, b).

The epandrium is broad basally and nearly parallel apically. Two short, round-tipped cerci are born on the lateral sides of abdominal segment XI (A11) and extend out from below the epandrium (Fig. 2b).

The hypandrium consists of a long broad basal stalk and a pair of short distal hypovalves (Figs 2e, f). Each hypovalve has a rounded incrassate process, which is situated basally on the inner margin of the hypovalve and covered with spinules on the dorsal surface (Fig. 2f).


Fig. 2. Male and female genitalia of Panorpodes kuandianensis. a, male genital bulb in ventral view, with the hypandrium removed; b, the same, dorsal view; c, gonostylus, mesal view; d, gonostylus, dorsal view; e, hypandrium, ventral view; f, hypandrium, dorsal view; g, terminal end of female abdomen in dorsal view; h, the same, ventral view. BP, basal process; BS, basal stalk; BT, basal tooth; Ce, cercus; Ep, epandrium; Gc, gonocoxite; Gs, gonostylus; Hv, hypovalve; IP, incrassate process; Pm, paramere; SP, subgenital plate; T9−T10, tergum IX−X.

The paired gonocoxites fuse basally to form a U-shaped concavity from the middle part to accommodate the aedeagus centrally (Fig. 2a). Each gonostylus has a prominent lobe-like basal tooth and a well-developed finger-shaped basal process. The elongate basal process bears numerous conical sensilla (Figs 2c, d).

Each paramere is composed of an applanate ventral branch, a strongly-sclerotized dorsal branch with a lateral process arising from the middle part, and a slender basal stalk. The parameres cling to the aedeagus, so that the ventral branches are unable to stretch ventrally from the aedeagus (Figs 2a, 3b).

The aedeagus is an interconnecting organ of the male, and consists of a pair of ventral valves, a pair of dorsal valves, and a central phallotreme. The ventral valves are usually concealed by parameres (Figs 3a, b).


Fig. 3. Male aedeagus and female genital plate of Panorpodes kuandianensis. a, aedeagus, dorsal view; b, aedeagus, caudal view; c, genital plate, caudoventral view; d, genital plate, caudal view. CP, copulatory pore; DP, dorsal paramere; DPr, dorsal process; DV, dorsal valve; LP, lateral process; Pt, phallotreme; SA, sculptured area; VP, ventral paramere; VV, ventral valve.

The female genitalia consist mainly of a genital plate and a subgenital plate (Figs 2g, h). The subgenital plate is oblong with two weakly-sclerotized sclerotomes (Fig. 2h). The two sclerotomes curve dorsally to form a genital chamber, inside which the genital plate is situated.

The female genital plate is a short strongly-sclerotized structure, situated at the base of the genital chamber. The orifice of the spermathecal duct is located ventrally at the sub-apical area of the genital plate distal to the sculptured area (Figs 3c, d).

Coupling of the genitalia

The claspers and other grasping devices of the male grasp the terminal end of the female abdomen to establish the coupling of the genitalia (Figs 4, 5). The hypovalves with incrassate processes seize the female cerci and cause the cerci to bend dorsad (Figs 4, 5a, b). The finger-like basal processes of the male gonostyli clasp the rotated genital segments of the female (Figs 4a, 5b, d). The paired lobe-like basal teeth seize the rear area of the genital chamber (Figs 4b, 5c).


Fig. 4. Schematic drawings of the coupling status of Panorpodes kuandianensis. a, schematic drawing of the male grasps the abdominal end of female by grasping devices; b, schematic drawing of the aedeagus and the genital plate contact in the female genital chamber in copulation. BP, basal process; Ce, cercus; DP, dorsal paramere; DPr, dorsal process; Ep, epandrium; GP, genital plate; Gc, gonocoxite; Gs, gonostylus; Hv, hypovalve; LP, lateral process; Pm, paramere; SP, subgenital plate; S6, sternum VI; T6−T9, tergum VI−IX; VP, ventral paramere; *, the position of the basal tooth clamping the genital chamber.

Copulatory mechanism

When the female is under control, the male seizes her cerci with his hypovalves and opens her genital chamber. After that, the male inserts his aedeagus into her genital chamber, with the lateral membranes of the female A9 obstructing the paired lateral processes into the genital chamber (Fig. 4b). Then the male adjusts his posture, thus enabling the phallotreme to contact the copulatory pore of the female to deliver his sperm ejaculates into the female spermatheca. During copulation the male keeps the stability of genital connection by using the lobe-like basal teeth of his gonostyli to restrict the movement of the genital plate (Figs 4b, 5c) and utilizing the basal processes of his gonostyli to prevent the female abdomen from shaking off the male control. The coupling genital structures mesh completely when the mating position changes from a V-shape to an end-to-end position.

Torsion of the female abdomen

The abdominal segments of female P. kuandianensis are unique in that the abdominal segments VII and VIII (A7 and A8) and the most part of A9 are usually concealed within abdominal segment VI (A6). In the process of position-change, the terminal abdomen of the female undergoes a rotation clockwise or anticlockwise (Figs 5c, d). The abdominal segments are recurved upward when the paired male and female sustain a V-shape mating position. When the mating position changes to end-to-end, A7 of the female is twisted a very small angle, A8 is twisted ~60° (Figs 4, 5c, b) and A9 is twisted ~120° (Figs 4, 5d). The torsion of the female abdomen results from the deformation of the intersegmental membrane.


Fig. 5. Coupling genitalia and torsion of the female abdomen. a, coupling genitalia in lateral view; b, the same, with the hypandrium removed to show the cerci of the female and the basal process of the male; c, the torsion of the female abdominal segments VII−VIII, lateral view, with the epandrium removed to show the subgenital plate of the female and the basal tooth of the male; d, the torsion of the female abdominal segments VII−IX, lateral view. BP, basal process; BT, basal tooth; Ce, cercus; Ep, epandrium; Gc, gonocoxite; Gs, gonostylus; Hv, hypovalve; Pm, paramere; SP, subgenital plate; S6, sternum VI; T6−T9, tergum VI−IX.