Nemoura nigrodentata Zhiltzova, 1980

Teslenko, Valentina A., 2017, Larvae of three East-Asian species of Nemoura (Plecoptera: Nemouridae), Zootaxa 4282 (2), pp. 309-323 : 317-323

Nemoura nigrodentata Zhiltzova, 1980

( Figs. 23–41 )

Zhiltzova, 1980, Insects of Mongolia 7:28, figs. 1‾5 (original description of male (epiproct, cerci) and female (without illustration)); Zhiltzova, 2003, Fauna of Russia and Neighbouring Countries New Series No. 145:272, figs. 437-439 (epiproct, cerci) and female (without illustration)).

Material examined. RFE. Paratypes. N 310-1973. Khabarovsky Region : 8 males, 13 females, 6– 11.06.1969, coll. P.I. Yurchenko . 5 males, 5 females, Chirka River , Ussuri R. Basin, Amur R. Basin, near road Vladivostok- Khabarovsk, coll. I.M. Levanidova ; 9 males, 15 females, 7 km from the mouth of Seuchi R., stream near the road, Sukpai R., Khor R. Basin, Amur R. Basin, 22.06.1998, coll. V.A. Teslenko ; Primorsky Region: 7 males, 15 females, Vasil’evka River , Rakovka R. Basin, Razdol’naya R. Basin, near stable, 30.05.1990, coll. T.S. Vshivkova ; 1 male, Rakovka R., Razdol’naya R. Basin, 7.06.2011, coll. M.P. Tiunov; 7 larvae, Nadezhdinsky district, small unnamed stream near Kiparisovo railway station (about 54 km to WN from Vladivostok ), 28.05.1994, coll. T.I. Arefina-Armitage ; Amurskaya Oblast’ : 5 males, 9 females, 12 larvae, Talago-3 stream, Byssa R. Basin, Selemdzha R. Basin, Zeya R. Basin, Amur R. Basin, under the bridge, 15.06.2004, coll. V.A. Teslenko ; Transbaikalia: 10 males, 7 females, 2 larvae, “ Mountain Steppe ” Reserve, Galzuty stream, Onon R. Basin, Amur R. Basin, 12.06.2010, coll. M.P. Tiunov .

Supplementary description. Male. Paraprocts wide, each inner lobe narrow, sclerotized and hidden under outer lobe, indistinctly outlined at the base, bluntly truncated distally, with rounded corners and slightly concave posterior margin, from under which a light membranous fold with an elongated posterior-external angle visible ( Fig. 23 ). Cerci strongly sclerotized. Each cercus bears a conspicuous dorsal tooth, a strong single hook bent obliquely upward with slightly swollen membranous inner lobe at the distal portion covered with long hairs; the outer apical portion of cercus wide, sclerotized and ending a row of 7 small pointed teeth; the inner apical part of cercus bears a single beak-shaped tooth with large swollen membranous lobe which is ball-shaped at the apex and has a long, dense hairs with heavy sclerotized bases ( Figs. 23, 24 ). Epiproct widened posteriorly from midlength, became narrow basolaterally ( Fig. 25 ). Pair of the lateral arms of the dorsal sclerite heel-shaped at the tips, directed obliquely down towards the middle, and nearly touching, distinctly sclerotized on the posterior and lateral margins; the pair of the dorsal folds deep and covered with comb-like scales ( Fig. 25 ). The basal plate of the ventral sclerite bears the spines arranged in two longitudinal rows, 12–14 spines in each row ( Fig. 26 ). Tip of the epiproct bilaterally symmetrical, rounded; the apical sclerite extends beyond dorsal folds; each apex of apical sclerite combshaped, directed outward, slightly bent downward with rounded anterior and inner edges, outer edge bears fine comb-like scales and two outwardly directed relatively stout straight spines ( Fig. 25 ). In dorsal view the apical sclerite and ring sclerite stand at an obtuse angle to each other and are connected in an oblique curve ( Fig. 25 ).

Female. Sternum 7 extended medially forming a well-developed, broadly rounded and strongly swollen pregenital plate, overlapping sternum 8 completely and anterior margin of sternum 9 partially ( Fig. 27 ). Posterior margin of pregenital plate dark sclerotized, anterior edge mostly membranous ( Fig. 27 ). In cleared slide mounted genitalia sternum 8 with paired semi round unpigmented vaginal lobes positioned laterally to genital opening; a pair of sclerotized rounded and swollen vaginal lobes flanks to unpigmented vaginal lobes ( Fig. 28 ). Subgenital plate difficult to distinguish, appearing as membranous fine folds mediobasally to genital opening. Vaginal pouch large, bell-shaped; dorsal face anteriorly with wrinkled shield; a pair of sclerotized internally roughened pockets inside of pouch hidden under folds, a pair of strongly sclerotized bean-shaped vaginal sclerites; to which bases a paired rounded or ball-shaped vaginal sclerites are attached ( Fig. 28 ). Sternum 9 slightly sclerotized, swollen anteromedially, with a pair of lateral dark spots on anterior margin and dark patch on posterior margin medially ( Fig. 28 ).

Notes. The male paratypes resemble illustrations of the original description. However, these illustrations do not show the two outwardly directed stout straight spines on the outer edge of the apical sclerite of the epiproct. Apparently these spines are clearly visible at magnification of 200Χ, and are not apparent when using a standard binocular microscope. These spines probably were overlooked in the original description. Presence of such spines at the outer edge of the apical sclerite base in the Asian N. lazoensis Zwick, 2010 and N. gemma Ham & Lee, 1998 suggesting affinities among these species. However, N. nigrodentata is readily distinguished by conspicuous cercal dorsal sclerite, which is heavy sclerotized, strong, and hook-shaped, additionally each cercus bears 7 small teeth on outer apical edge, and single beak-shaped tooth on inner edge. These features are diagnostic for N. nigrodentata .

Mature larvae. Body length 5.7–6.2 mm in males; 5.9–7.3 mm in females. General color brown ( Fig. 29). Head with a conspicuous pattern consisting of dark brown tentorial callosities and three pairs of patches on occiput, clypeus medially with pair of <-shaped thread-like figure, directed to anterior ocellus, corners of clypeus pale ( Figs. 29, 30). Antenna short, not exceeding 87% of body length, scape and pedicle brown. Pronotum approximately 1.6Χ wider than long, pattern distinct, Х-shaped, with a few narrow “branches” ( Figs. 29, 30). Mesonotum and metanotum brown with diffuse pale patches. Fore femur 2.4Χ longer than wide ( Fig. 36 ), the hind femur 3.6Χ longer than wide. Abdominal terga brown, integument light, matte in appearance ( Fig. 30). Cerci relatively short with 24–25 segments; length not exceeding 90% of body length ( Figs. 29, 38 ).

Setation. Setal fringe around the pronotum consists of occasional long slender acute bristles and cylindrical bristles with blunted apices; length of cylindrical blunt bristles on lateral margins and anterior and posterior corners greater than on anterior and posterior margins mesally ( Figs. 31–34 ). Length of the longest cylindrical bristles at posterior pronotal corners attain 5.5% of pronotal width; length of the long slender acute bristles on posterior margin reaches 10% of pronotal width ( Figs. 33, 34 ). Occasional long hairs, short club-shaped setae with irregularly notched apices, and tiny procumbent setae with acute hooked apices cover pronotal disc ( Figs. 31, 32 ). Outer wing pad margin bears slender acute bristles; delicate short acute setae in the lines on the wing-pads ( Fig. 35 ). Setal fringe on the outer femur margin includes a few long thin hairs and long acute bristles in irregular arrangement ( Fig. 36 ) the longest acute bristles reach 63% of femur width on the fore leg and 45% on the hind leg. Femur covered with cylindrical short bristles, blunted to the apices; fine procumbent setae and relatively long slender acute bristles. Setation of tibia features stout spine-shaped bristles sometimes with blunt apices, outer margins with long hairs ( Fig. 36 ). Terga covered with tiny procumbent setae and mainly short cylindrical bristles with blunt apices ( Fig. 37 ). Along the posterior tergal margin cylindrical bristles with blunt apices concentrated in the middle of; long slender acute bristles close to lateral edges ( Fig. 37 ); length of the longest acute bristles attains 54% of segment length on terga 5¯6 ( Fig. 37 ). Cerci with slender acute bristles in the apical whorl, intercalary setation well visible, especially on distal cercal segments ( Figs. 39–41 ). Apical whorl of basal cercal segments, the slender acute bristles longer the segment; the longest cylindrical bristles 132–137% of segment’s length on cercal segment 8–9 ( Fig. 39 ); apical whorl of 15–16 cercal segments the longest bristles not exceeding 64% of the segment length ( Fig. 40 ), length of the intercalary setae approximately equals 42% of segment length; setal ring of apical cercal segments sparse, length a few thin hairs fits to 46% of segment length ( Fig. 41 ), length of intercalary setae not exceeding 28% of apical segment length ( Fig. 41 ).

Diagnosis. The larvae of N. nigrodentata can be distinguished from the other known Nemoura larvae by the conspicuous head pattern, the relatively short antenna and the cerci which do not exceed the body length. The setation is uniform, consisting of cylindrical bristles with blunt apices at the margin of the pronotum, on the surface of the femur and abdominal segments, on the outer femur and wing pad margins, and the posterior tergal margins.

The cercal apical whorl bristles are long, slender, and acute. The length of the longest cylindrical bristles of the pronotal fringe does not exceed 5.5% of pronotal width; the length of the slender acute bristles attains 10% of pronotal width. The outer femur margin bears slender acute bristles in an irregular arrangement. The posterior tergal margins feature conspicuous slender acute bristles arranged laterally, the length of the longest attains 54% of segment length on terga 5¯6 ( Fig. 37 ). Cerci have uniform setation of slender acute bristles in the apical whorl, intercalary setation well pronounced, especially in the distal cercal segments. The slender acute bristles of the apical whorl of the basal cercal segments are 132–137% of the segment length. At the middle part of cerci, the longest bristles do not exceed 64% of the segment length, the length of the intercalary setae reaches 42% of the segment length; in the apical cercal segments, few thin hairs reach 46% of the segment length, the length of intercalary setae does not exceed 28% of the apical segment length.

Distribution. Nemoura nigrodentata is an East Asian mainland species, known from the Amur River Basin in Mongolia and RFE.

Figures

FIGURES 23 – 26. Male of Nemoura nigrodentata. 23. Abdominal tip, dorsal. 24. Cercus, dorsal. 25. Epiproct, dorsal. 26. Epiproct, ventral. Scale: 23, 25, 26 = 0.1 mm, 24 not to scale.

FIGURES 27 – 28. Female of Nemoura nigrodentata. 27. Abdominal tip, ventral. 28. Vaginal complex, cleared, dorsal. Sp – transversal folds of subgenital plate, pp – pregenital plate, s – anterior margin of sternum 9, vs – vaginal lobes, go – genital opening, o – oviduct, sh – shield, rp – roughened pocket, bvs – bean-shaped vaginal sclerite, rvs – rounded vaginal sclerite. Scale (mm): 27 not to scale; 28 = 0.1.

FIGURES 36 – 41. Larva of Nemoura nigrodentata. 36. Right fore leg. 37. Chaetotaxy of terga 5 – 6 (not cleared). 38. Left cercus. 39. Cercus segments 8 ‾ 10 with slender acute bristles. 40. Cercus segments 15 & 16 with slender acute bristles and intercalary setae. 41. Apical cercus segment with slender acute bristles and intercalary setae. Scale (mm): 36, 38 = 0.3; 39 – 41 = 0.1.

FIGURE 31 – 35. Larva of Nemoura nigrodentata. 31. Chaetotaxy on disc close to anterior pronotal margin. 32. Anterior pronotal margin, cylindrical bristles with blunted apices. 33. Fringe of bristles on left pronotal margin (not cleared). 34. Cylindrical bristles with blunted apices and slender acute bristles on left posterior corner. 35. Outer wing pad margin with slender acute bristles and delicate short acute setae in the lines on wing pads. Scale (mm): 31 – 35 = 0.1.