Paraleuctra cuihuashana, Chen, 2019

Chen, Zhi-Teng, 2019, The first formal report of brachypterous stonefly of Leuctridae (Plecoptera) from China, Zootaxa 4624 (2), pp. 230-240 : 231-236

Paraleuctra cuihuashana sp. nov.

Figs. 1–9.

Male (Figs. 1A, 2–6). Body length 5.0–6.0 mm; forewing length 2.5–3.0 mm, hindwings length 1.5–2.5 mm. In the forewing, one crossvein present between RA and RP; M forked with two branches fused apically; six crossveins present between M and CuA; nine crossveins present between CuA and CuP; AA1 simple; AA2 forked. In the hind wing, RP and M unforked; AA1 simple; AA2 forked with an incomplete branch.

Abdominal segments compactly connected; posterior half of tergum 10 strongly divided, forming a subtriangular concave; posterolateral margins of tergum 10 each connected with a dark sclerite, the sclerite broad at base and apically with a subquadrate projection, the base extending to ventral aspect of sternum 10. Vesicle of anteromedian margin of sternum 9 long oval, length about 1.5X longer than wide; subgenital plate trapezoidal with truncate apex and long hairs. Cerci dark sclerotized, strongly forked into two sharp prongs; upper prong longer than lower prong, basally with a subtriangular process in lateral view; inner surface of lower prong slightly humped; a pale, slender spine present near base of upper prong, projecting backwards; base of cerci slender, connected with lateral arms of the subanal probe; dorsobasal of cerci with a small, upcurved hook. Epiproct apically hook-shaped, basal part wide, dorsal surface with a row of several long bristles, apex with lateral spinules. Subanal probe present beneath the epiproct, slender and upcurved, fusiform in ventral view, with narrow base and apex.

Female (Figs. 1B, 7). Body length 6.0–8.0 mm. Forewings length 4.5–6.0 mm, hindwings length 2.5–4.0 mm. Head, thorax and appendages similar to males; abdominal segments 2–7 with dorsal, ventral and lateral stripes; intersegmental membrane of sterna 1–7 each with two small lateral spots. Wing venation varies among available specimens, but the anal field of hindwings always with three anal veins. Subgenital plate of sternum 8 darkly sclerotized and bilobed, each lobe with several long bristles. Posterior margin of sternum 9 membranous. Paraprocts subtriangular and divided. Cerci unsegmented, finger-shaped.

Type material. Holotype male, China: Shaanxi Province, Xi’an City, Cuihuashan National Geopark , fastflowing stream (Fig. 8), 1000–1200 m, 33°58′45″N, 108°59′45″E, 29 April 2019, leg. Zhi-Teng Chen ( ICJUST) . Paratypes: four males and four females, same date and locality as holotype ( ICJUST) .

Etymology. The species is named after the type locality, Cuihuashan National Geopark

Remarks. The females of P. cuihuashana exhibit variable length of wings from much shorter to slightly longer than the body length (Fig. 9). The new species is very similar to the macropterous P. orientalis collected from other stream sites in the Cuihuashan National Geopark, sharing similar color patterns and male and female terminalia. However, in P. orientalis , the dorsobasal stripes of femora are absent; and in the male, hindwing venation differs from P. cuihuashana and the cerci have no finger-shaped process, instead a minute subtriangular process ( Figs. 10–11 , also see fig. 14a in Li et al. 2010). The unique wing venation of P. cuihuashana is associated with the brachypterous condition. Abnormal wing venation or variations in wing venation sometimes occurs among specimens of a same genus or a same species in different localities, e.g. Lillehammer (1974) studied in detail this aspect in different stonefly genera including Leuctra . Other authors, such as Zwick & Weinzierl (1995) discussed this phenomenon in the Perlodidae that the development of crossveins and cells varies with body size and relative wing length, both between and within species.

The molecular data has shown a considerable large genetic distance (over 10%) between the brachypterous P. cuihuashana and the macropterous P. orientalis ( Table 1 ); this value is much larger than the commonly used 2% ( Hebert et al. 2003, Zhou et al. 2009). In the Neighbor-joining (NJ) tree ( Fig. 12 ), the macropterous male and female of P. orientalis are grouped in the same clade, separated from the clade of brachypterous males and females of P. cuihuashana . Topology of the NJ tree is highly supported with high support values on most nodes. Molecular data used in this study has proved its efficiency in identifying the morphologically similar species such as those in genus Paraleuctra . Cerci of P. cuihuashana are also similar to P. qilianshana Li & Yang, 2013 (see fig. 7 in Kong et al. 2013), however, the two species can be easily separated by the shape of sclerite posterior to tergum 10 (see fig. 2 in Kong et al. 2013).

Factors probably related to the brachypterous condition of stonefly adults include environmental factors such as water temperature, altitude, nutrition, and genetic factors ( Hynes 1976, Donald & Patriquin 1983, Brittain 1990, Westermann 1993). Adults of P. cuihuashana were collected from the streamside grasses near a pool/run, where the water flow is reduced (Fig. 8). It would be of interest to determine the cause of the brachyptery of the new species.

Figures

FIGURE 10. Paraleuctra orientalis (Chu, 1928). A. right forewing, dorsal view; B. right hindwing, dorsal view.

FIGURE 11. Paraleuctra orientalis (Chu, 1928). A. male terminalia, dorsal view; B. male terminalia, ventral view; C. male terminalia, lateral view; D. female terminalia, ventral view. The small subtriangular cercal spine is indicated with arrowhead.

FIGURE 12. Neighbor-joining tree of the three morphological types in this study. The three types are indicated with different colours. This tree recovered two distinct clades: Paraleuctra cuihuashana sp. nov. represented by A and B types; Paraleuctra orientalis represented by C type.