Agabus (Acatodes) abaensis, Šťastný, Jaroslav & Hájek, Jiří, 2016

Šťastný, Jaroslav & Hájek, Jiří, 2016, Agabus abaensis sp. nov., a peculiar species of the confinis - group from central China (Coleoptera: Dytiscidae: Agabinae), Zootaxa 4121 (3), pp. 311-318 : 312-316

Agabus (Acatodes) abaensis sp. nov.

( Figs. 1–8 )

Agabus n. sp. ( China): Fery 2011: 50, Fig. 39 (drawing of median lobe).

Type locality. China, Gansu province, Dagcanglhamo (= Langmusi), ca. 34.081N 102.639E, 3.420 m a.s.l.

Type material. Holotype Ƌ ( NMPC), labeled: “ CHINA: Gansu province / Dagcanglhamo (= Langmusi) / 3464–3644 m / 23.–25.VI.2005 / 34°04.6–05.1'N 102°37.7–38.1'E, / J. Hájek, D. Král & J. Růžička leg. // individually collected, grasslands, close valley with loess loam, stream, pools, margin of coniferous forest [printed] // HOLOTYPE / Agabus (Acatodes) / abaensis sp. nov. / J. Šťastný & J. Hájek det. 2013 [red label, printed]”. Paratypes: 4Ƌ, 14♀, same label data as holotype ( BMNH, IZCAS, NMPC, SYSU, ZSMG); 1Ƌ, 1♀, “ CHINA, NW Sichuan, 3500 m., / 15 km NW ABA, 33.00N / / 101.36E, border field/road / J.Rejsek leg., 29.–30.vii.2001, [printed]” ( JSCL); 1Ƌ, “ CHINA, N Sichuan, / pass 10 km E SANGARMAI, / 32.14N / 102.36E, 4300 m., / J.Rejsek leg., 8.–11.vii.2001, / alpine meadows/screes [printed]” ( JSCL); 1Ƌ, 2♀, “ CHINA, N Sichuan, / 25 km NNE ZHANGLA, 33.04N / 103.44E, 3500 m., / J.Rejsek leg., 3.–5.viii.2001 [printed]” ( JSCL, CHF). Each paratype is provided with the respective red printed label.

Description of the holotype. In dorsal view elongate oval, rather narrow (TL/MW: 1.9). Lateral outline weakly curved with a weak discontinuity at level of pronotal base in dorsal aspect ( Fig. 1 ). Broadest in elytral midlength. Entire surface weakly shiny.

Coloration. Head black; two posteromedial spots on vertex and narrow anterior margin of clypeus dark brown; labrum brownish; antenna testaceous basally, antennomeres V–XI reddish brown to piceous apically; maxillary and labial palpi testaceous, terminal palpomere of each palpus infuscate apically. Pronotum black with very narrow lateral bead dark rufous to piceous, postero- and anteromedially indistinctly reddish-brown translucent. Elytra dark brown to piceous; base, lateral margin, epipleura and humeral angles diffusely pale rufotestaceous. Ventral surface mainly black; posterior margin of metacoxal process and abdominal ventrites III–VI transparently rufous. Legs rufo-piceous; femora posteromedially piceous to black, dark coloration more extensive on metafemora than on pro- and mesofemora).

Surface sculpture and setation. Head. Frons anteriorly between eyes with two shallow oblique transverse grooves containing of irregular row of about seven deeply impressed punctures; along inner side of eyes with row of punctures. Setation absent. Reticulation simple, consisting of weakly impressed, more or less polygonal meshes of irregular size and shape; some meshes opened, occasionally also with central micropuncture; meshes more elongate along eyes.

Pronotum. Reticulation consisting of well impressed meshes of varying size and shape; some meshes opened, majority of meshes with 1–2 small distinct punctures inside. Meshes generally larger and shallower medially and smaller and more impressed laterally. Indistinct microreticulation perceptible only on sides of pronotum. Punctation consisting of irregular row of coarse setigerous punctures along margins; punctures coarser along anterior and posterior margin, finer along lateral margin. Punctures along anterior margin slightly sparser medially; posterior row of punctures broadly interrupted medially, but not interrupted sublaterally. Centre of pronotal disc with distinct longitudinal furrow.

Elytra with distinct double reticulation. Large meshes of varying shape and size well impressed; meshes rather broad (not elongate), on disc polygonal; some meshes with central puncture. Microreticulation presents on entire surface, slightly less distinct anteromesally, consisting of very fine, shallowly impressed polygonal meshes. Punctation consisting of coarse setigerous punctures arranged in sutural, two discal and two lateral longitudinal puncture lines; in second quarter of elytral length with few additional punctures between lines; lines become very irregular in apical quarter.

Ventral side with almost entire surface reticulated. Genae with moderately large transverse meshes; prosternum with small meshes except for glabrous tectiform medial part; legs, meso- and metaventrite with small transverse meshes; metacoxal plates with double reticulation, large meshes elongate, small meshes almost isodiametric; abdominal ventrites I–V with transverse meshes medially and oblique meshes laterally; abdominal ventrite VI with double reticulation. Punctation consisting of coarse setigerous punctures on gula, prosternum, legs, and abdominal ventrites; on ventrites arranged in transverse lines; fine punctures present on prosternal process and sparsely distributed on metaventrite. Most of ventral surface covered with strioles; strioles short and transverse on metaventrite, longitudinal on metacoxae, and very long, medially transverse and laterally oblique on abdominal ventrites.

Structures. Head moderately broad, head basal width/maximal pronotal width about 0.63; clypeus with anterior bead narrow and complete. Pronotum broad, maximal pronotal width/pronotal length 2.5, in dorsal view with sides very slightly arcuate, weakly curved before anterior and posterior angles; posterior angles rectangular with obtuse tips, anterior angles acute with tuft of thick golden setae; anterior bead fine, broadly interrupted in middle, lateral bead relatively narrow and well-marked except for anterior angles. Prosternum broadly rounded in cross-section. Prosternum between procoxae tectiform in cross-section, with midline of convexity rounded; blade of prosternal process lanceolate, flat or weakly convex, apex sharply acuminate; lateral beading narrow but distinct, vanishing before apex. Metaventrite with anteromedial process bluntly pointed anteriorly, reaching mesoventral fork beyond midlength of mesocoxae; process with anteromedial impression for reception of prosternal blade almost attaining level of posterior margin of mesocoxae; “metaventral (metasternal) wings” broadly triangular, WC/WS 2.0. Lines of metacoxal processes diverging anteriorly, reaching posterior margin of metaventrite. Abdominal ventrite VI with posterior margin evenly rounded with well-defined beading. Pro- and mesotarsomeres I–III moderately broadly dilated, ventrally with numerous very small, similar sized, slightly ovate suckers on long stalk and some adhesive setae; protarsal claws elongate and relatively straight, strongly curved near apex, anterior claw with ventral tooth ( Fig. 8 ), somewhat shorter than protarsomere V (protarsomere V is 1.5 times as long as protarsal claws), posterior claw very slightly shorter than anterior one; mesotarsal claws rather short, widened; metatarsomere I being 1.3 times as long as longer (posterior) tibial spur; metatarsomere V long, ca. 2.1 times longer than metatarsomere IV; metatarsal claws equal in length, arcuate.

Male genitalia. Median lobe robust with large base, in natural position apically turned to right in ventral aspect ( Fig. 4 ), apex with subapical dorsal spine in lateral view ( Fig. 3 ), ventral groove more or less straight and open over entire length. Parameres ( Fig. 5 ) stylate, with triangular basal part sclerotised, apex with short appendage; apex and mesal margin densely setose, apically with longer setation.

Variability. All specimens of the type series agree well with the holotype. The specimens show variation in body size, in extent of piceous coloration of lateral beading of the pronotum, in the dark brown coloration on the elytra, and in the sinuation of lateral sides of the pronotum.

Females differ from males in the following characters: color of elytra very slightly lighter, meshes of dorsal surface reticulation slightly larger and more deeply impressed than in male, hence elytra appearing rather submatt ( Fig. 2 ); pro- and mesotarsomeres I–III not dilated and without adhesive setae; protarsal claws thin, without a ventral tooth, posterior protarsal claw slightly shorter then anterior one; mesotarsal claws longer than in male, thin and evenly curved. Gonocoxa and tergite IX as in Fig. 6 , gonocoxosternum as in Fig. 7 .

Measurements. Holotype: TL = 7.9 mm, TL-h = 7.4 mm, MW = 4.2 mm, TL-h/MW = 1.76; male paratypes: TL = 7.6–8.5 mm (8.08± 0.3 mm), TL-h = 7.0– 7.7 mm (7.33± 0.22 mm), MW = 4.1–4.4 mm (4.19± 0.09 mm), TL-h/MW = 1.70–1.83; (1.53± 0.38 mm); female paratypes: TL = 7.8–8.2 mm (8.01± 0.16 mm), TL-h = 7.1–7.4 mm (7.26± 0.11 mm), MW = 3.9–4.1 mm (4.04± 0.06 mm), TL-h/MW = 1.76–1.85; (1.80± 0.02 mm).

Differential diagnosis. With the presence of subapical dorsal spine on the median lobe of male, the new species is without any doubt classified in the subgenus Acatodes sensu Nilsson (2000) . More precisely, Agabus abaensis sp. nov. is assigned to the A. confinis species group as defined by Larson (1989, 1991) and Nilsson (1990) based on: 1) narrow anterior bead of clypeus; 2) pronotum without broad yellow lateral stripes; 3) posterior angles of pronotum rectangular; 4) apex of prosternal process elongate and pointed; 5) metaventrite with anteromedial emargination long, reaching level of posterior margin of mesocoxae; 6) male pro- and mesotarsomeres I–III moderately dilated, ventrally with numerous small elongate adhesive setae; 7) metatibia impunctate on posteroventral margin; 8) metatarsomere V more than 1.5 times longer than metatarsomere IV; 9) shape of base of male median lobe; and 10) paramere stylate. Agabus abaensis sp. nov. differs from all other species in the group by the combination of the following characters: elytral sculpture with considerably large, distinctly double reticulation in both sexes, male anterior protarsal claw dentate, and shape of male median lobe.

Etymology. The new species is named after its area of occurrence—the Aba region (formally Ngawa Tibetan and Qiang Autonomous Prefecture) in Sichuan, bordering on Gansu province in the north; the specific epithet is an adjective in the nominative case.

Collecting circumstances. At the type locality, Agabus abaensis sp. nov. was collected in pools in grassland ( Fig. 9 ). The new species was found in a species rich Dytiscidae association, together with Agabus brandti Harold, 1880 , A. lobonyx Guignot, 1952 , Boreonectes emmerichi (Falkenström, 1936) , Hydroporus nanpingensis Toledo & Mazzoldi, 1996 , Hygrotus impressopunctatus (Schaller, 1783) , H. zigetangco Fery, 2003 , Ilybius cinctus Sharp, 1878 , I. obtusus Sharp, 1882 and Nebrioporus formaster (Zaitzev, 1908) .

Distribution. So far known from several localities in south-western Gansu and northern Sichuan provinces, at the eastern border of the Tibetan plateau, China ( Fig. 10 ).

Figures

FIGURE 9. Type locality of Agabus abaensis sp. nov.: pools near Langmusi.

FIGURE 10. Distributional map of Agabus abaensis sp. nov.

FIGURES 1 – 2. Habitus of Agabus abaensis sp. nov.: 1. male holotype; 2. female paratype.

FIGURES 3 – 8. Agabus abaensis sp. nov.: 3. median lobe of aedeagus in lateral view; 4. same in ventral view; 5. paramere; 6. gonocoxa and tergit IX; 7. gonocoxosternum; 8. male protarsus.