Sinacroneuria obscura Li & Murányi, 2017

Li, Weihai, Murányi, Dávid, Orci, Kirill Márk, Uchida, Shigekazu & Wang, Rongfeng, 2017, A new species of Sinacroneuria (Plecoptera: Perlidae) from Guangxi Zhuang Autonomous Region, southcentral China based on male adult, larva and drumming signals, and validation of the Japanese species of the genus, Zootaxa 4299 (1), pp. 95-108 : 96-101

Sinacroneuria obscura Li & Murányi , sp.n.

( Figs. 1–37 )

Type materials: Holotype male ( HIST), China: Guangxi Zhuang Autonomous Region, Shangsi County, Shiwandashan National Forest Park, Pearl River above tourist route bridge, 375 m, 21°59.913'N, 107°54.283'E, 2015 . III.27, leg. J. Kontschán, J.Y. Li, S. Li, W.H. Li, D. Murányi, G.Q. Wang. Paratypes: same locality and date: 2 male and 1 female penultimate larvae, 2 male exuviae ( HNHM: No. PLO86) ; same locality but collected on 2015. III.28: 2 male and 1 female exuviae ( HIST), 1 adult male, 1 female larva, 5 male and 1 female exuviae ( HNHM: No. PLO100); Shiwandashan National Forest Park, small forest brook, 365 m, 21°50.574'N, 107°51.802'E, 2015 . III.28, leg. J. Kontschán, W.H. Li, D. Murányi, G.Q. Wang: 1 male exuviae ( HNHM: No PLO115).

Adult. General body color yellow brown. Biocellate, vestigial anterior ocellus a small dark spot. Distance between ocelli almost two times the diameter of the ocellus. Head with dark brown area covering ocellar triangle, slightly extending laterally under pale M line; lappets dark and triangular mark forward of M-line brown to brownish ( Fig. 1 ); compound eyes black; antennae brown. Pronotum brownish with dark rugosities ( Fig. 1 ); wing membrane transparent, veins brown; legs brownish. Abdominal segments pale brown to brownish.

Male. Forewing length holotype ca. 14.9 mm, paratype 15.0 mm. Tergum 9 posterior margin slightly produced, with two far sensilla patches, each consisting of many larger triangular sensilla basiconica ( Fig. 2 ). Sensilla basiconica patch of tergum 10 divided medially distance between patches ca. 1.5X diameter of the patch ( Fig. 2 ). Paraprocts heavily sclerotized, with small, nipple like tips ( Figs. 2, 5 ). Sternum 9 with sclerotized posterior margin fringed with short hairs, hammer oval-shaped, slightly elevated in lateral view ( Fig. 3 ); hammer bare but surrounded by strong hairs, anterior hairs heavier; below hammer is a patch of brown hairs giving appearance of brown pigmentation ( Fig. 4 ). Aedeagus ( Figs. 4 , 7–8 ): basoventral area with large patch of setal hairs, apical membrane forming a large dorsal and a small ventral globes; median sclerite absent, replacing with a patch of tiny spines on the ventral globe; Y-arms about 3 times as long as stem, basal trunk of Y-arms nearly parallel-sided, the apex of Y-arms sharp and horn-like, curved outward and upward. ( Fig. 8 ).

Female. Unknown.

Larva. Body length of the female larva 17 mm, male exuviae 12-13 mm, female exuviae 17–18.5 mm; no last instar male larva available. General colour pale but with distinct dark markings on dorsal surface ( Fig. 9 ); ventral surface generally pale ( Fig. 10 ). Head yellow with transverse dark stripe posterior to M-line, anterolateral edges are also dark; occipital area not elongated, eyes normal sized. Biocellate, distance between ocelli about twice as wide as diameter of one ocellus. Lacks occipital ridge and row of occipital setae, occipital suture indistinct; only few, relatively long, pale setae occur posterior to eyes, while most of the head covered by fine, black clothing hairs ( Fig. 21 ). Antenna yellowish, palpi pale. Postmentum undivided ( Fig. 27 ), glossa and paraglossa usual for the family ( Figs. 28–29 ). Lacinia bidentate, apical tooth much longer than subapical tooth, marginal fringe consist of only 8–9 strong setae; galea as long as apical tooth of lacinia, bear only apical setae ( Figs. 22–23 ). Mandible wide, having two molar and two incisor dens, molar brush short but dense ( Figs. 24–26 ). Labrum mostly dark brown, with downcurved posteromedial lobe bearing dense setae ( Figs. 30–31 ); hypoharynx simple, with short apical setae ( Fig. 32 ). Pronotum with rounded corners, less than twice wider than long, marginal row of setae laterally incomplete; all thoracic segments covered only by fine, black clothing hairs, and dark coloration is limited to marginal areas ( Fig. 9 ). Mesosternum with long furcasternal pit, furcasternal arms short and laterally positioned ( Figs. 10 , 12 ). Thoracic gills short and with dense chloride cells ( Fig. 11 ); prothorax with one anterior and one posterior supracoxal gill; mesothorax with two anterior sternal gills one of which is deeply divided, one anterior and one posterior supracoxal gill; metathorax with two anterior sternal gills one of which is deeply divided, one anterior and two posterior supracoxal gill ( Fig. 12 ). Proventricular teeth uniform and regularly placed ( Figs. 17– 18 ). Legs long, dorsal row of swimming hairs scarce and indistinct on femora, more developed on tibiae; surface setation consist of black clothing hairs and scarce, pale and moderately long setae ( Figs. 15–16 ). Abdomen with terga 1–3 and 7–8 mostly pale, while terga 4–6 and 9–10 contrastingly dark ( Fig. 9 ). All terga bear dense apical row of shorter and very long setae mixed, that are pale and easily broken; similar setae are placed in an irregular, transverse median row on the terga, while most of the surface is covered with fine, black clothing hairs, easily detached but represented as fine punctuations ( Fig. 19 ). Clothing hairs similar on sterna, but the apical row medially widely interrupted on sterna 2–7, complete on sterna 8–10 in case of males while on female sternum 8 it is narrowly interrupted by the shallow genital notch ( Fig. 20 ); median row of setae complete only on sternum 10.

Paraproct simple, bears small anal gill ( Figs. 9–10 , 14 ). Cercus long, lacks swimming hairs but elongated hairs of the medial row are forming distinct tufts on the inner surface of cercomeres; further portions of the row consist of long but not erect, pale setae mixed with long, fine hairs ( Figs. 13–14 ).

Drumming. Four drumming calls of only one male were recorded; therefore the present description of the male vibrational signal of the species should be regarded as preliminary revealing only the major rhythmic features of the vibratory male calls of this species. The duration and count values given in parentheses report the range measured in the signals of the studied specimen recorded at an ambient air temperature of 19.4o C. The drumming call of S. obscura consists of two beat groups ( Fig. 33 a). The first longer beat group (32-35 beats, duration between 732-838 ms) is followed by a second shorter beat group (5 beats invariably, duration 103-107 ms) after an interval shorter than the first beat group (inter beat group interval varied between 239-273 ms). In both beat groups, beat amplitude increases during the course of the group. In the first beat group beat intervals vary between 15-20 ms during the first low amplitude part (values above 30 ms occurs probably as a result of missing beats) and between 20-25 ms during the final high amplitude part ( Fig. 33 b). A short transitional part in the middle of the beat group can be observed where beat intervals show a tendentious increase. The second beat group beat intervals vary from 20-25 with an uncertain decreasing tendency ( Fig. 33 c).

Distribution and ecology. The new species was collected from Pearl River, a submontane river and a small forest brook in the Shiwandashan National Forest Park, Guangxi Zhuang Autonomous Region of southcentral China. The Shiwandashan Mountains are part of a moderately high coastal range on the border of China and northeastern Vietnam, being relatively isolated from the main mountain chains of both Indochina and the southern Chinese mountain ranges. At the type locality, the Pearl River flows in dense, evergreen submontane forest at moderately low elevation, having fast flow with several cascades, and a rocky bed with very few organic deposits and coarse sand patches among the large rocks and stones ( Figs. 34–36 ). The stonefly fauna of the river is rather rich, besides the new species, twelve species (two Leuctridae , four Nemouridae , six Perlidae ) were found, among them further three are new and will be described in a future paper, including a new Rhopalopsole Klapálek, 1912 species having been published recently ( Li et al. 2017). The forest brook, a tributary of the Pinglong River, where we found a single exuviae, has reduced flow and is shallow but similar rocky bed as the Pearl River ( Fig. 37 ). Here the new species was found together with a another Perlidae , one Leuctridae and two Nemouridae species. According to high number of exuviae observed on emergent rocks, the new species appears relatively common in the Pearl River. Peak emergence apparently was completed by the time of our late March collecting, as we found only a single last instar larva despite several hours of searching.

Etymology. The name obscura (from the Latin word obscurus, meaning obscure) refers to the reduced anterior ocellus. Used as an adjective, gender feminine.

Remarks. The new species is similar to S. biocellata Stark & Sivec, 2008 from Vietnam, by sharing similar head pattern and two ocelli, and to S. bicornuata Stark & Sivec, 2008 from Sichuan Province of southwestern China by absence of median sclerite in ventral surface of aedeagus. It may be easily separated by the latter by nearly divided sensilla basiconica patch of tergum 9 and parallel-sided basal trunk of Y-arms ( Figs. 2 , 7 ). The sensilla basiconica patch of tergum 9 in both S. biocellata and S. bicornuata are apparently fused ( Figs. 2, 5 in Stark & Sivec 2008, Fig. 3 a in Li et al. 2014). Only the larva of S. obscura and S. acuticornis sp. n. are known. The two species are being rather similar, but can be separated on the basis of different abdominal dorsal pattern ( Fig. 9 , compared to Fig. 14.4 in Shimizu et al. 2005).

Figures

FIGURE 33. Drumming call of Sinacroneuria obscura sp. n. (a) an oscillogram of a call; (b) a scatter plot presenting how beat intervals vary during the first beat group of the call (serial numbers of beat intervals indicate their order of occurrence; each + sign show a single measurement data; a small amount of noise was added to the horizontal coordinates to make each sign more easy to see); (c) a scatter plot of beat interval variation during the second beat group.

FIGURES 1 – 6. Sinacroneuria obscura Li & Murányi, sp. n., holotype male. — 1: head and pronotum, dorsal view; 2: terminalia, dorsal view; 3: terminalia, ventral view; 4: terminalia, lateral view; 5: paraproct, dorsal view; 6: hammer of sternum 9, ventral view—not to scale.

FIGURES 7 – 8. Sinacroneuria obscura Li & Murányi, sp. n., holotype male. — 7: aedeagus, dorsal view; 8: aedeagus, lateral view, with details of spines in lateral and caudal view—not to scale.

FIGURES 9 – 10. Sinacroneuria obscura Li & Murányi, sp. n., female larva. — 9: habitus, dorsal view; 10: habitus, ventral view—scale 1 mm.

FIGURES 11 – 16. Sinacroneuria obscura Li & Murányi, sp. n., female larva and exuviae. — 11: gill AT 3, ventral view; 12: diagrammatic figure of thoracal gills arrangement, ventral view; 13: 10 – 11 th cercal segments, ventral view; 14: basal half of cerci, ventral view; 15: left hind leg, dorsal view; 16: left hind leg, ventral view—scales 1 mm for Figs. 12, 15 – 16, 0.5 mm for Fig. 13, Figs 11, 14 not to scale.

FIGURES 17 – 21. Sinacroneuria obscura Li & Murányi, sp. n., female larva and exuviae. — 17: proventriculus, dissected; 18: details of proventricular teeth; 19: setation of tergum 5 medial half, dorsal view; 20: setation of sternum 8 medial half, ventral view; 21: setation of the left occipital area of the head, dorsal view—scales 1 mm, Fig. 18 not to scale.

FIGURES 22 – 32. Sinacroneuria obscura Li & Murányi, sp. n., female exuviae. — 22: right maxilla, ventral view; 23: right maxilla, dorsal view; 24: right mandibula, ventral view; 25: right mandibula, dorsal view; 26: right mandibula, caudal view; 27: labium, ventral view; 28: glossa and paraglossa, ventral view; 29: glossa and paraglossa, dorsal view; 30: labrum, ventral view; 31: labrum, dorsal view; 32: hypopharynx, ventral view—scale 1 mm, Fig. 27 not to scale.

FIGURES 34 – 37. Type localities of Sinacroneuria obscura Li & Murányi, sp. n., China: Guangxi Zhuang Autonomous region, Shangsi County, Shiwandashan National Forest Park. — 34: Pearl River, downstream view from the type locality; 35: Pearl River, upstream view from the type locality; 36: Pearl River at the type locality; 37: forest stream tributary of the Pinglong River.