Pleciobates expositus Jehamalar, Chandra & Zettel

Jehamalar, E. Eyarin, Chandra, Kailash, Zettel, Herbert, Basu, Srimoyee, Barman, Bijita, Gupta, Susmita & Subramanian, K. A., 2014, Two new species of Pleciobates (Hemiptera: Gerromorpha: Gerridae) from India, with a key to the species of Pleciobates, Zootaxa 3866 (3), pp. 435-445 : 440-443

Pleciobates expositus Jehamalar, Chandra & Zettel , NEW SPECIES

( Figs. 2A–M )

Material examined. Holotype (apterous male): INDIA, ASSAM, Dhubri District, Chakrashila Wildlife Sanctuary, Jornagra Stream, 284 ft [86.5 m a.s.l.], N 26°17’18.2’’, E 90°20’49.5’’, 17.vii.2011, coll. Bijita Barman. Paratypes. 4 apterous female, same data as for holotype. 1 apterous female, ASSAM, Dhubri District, Chakrashila Wildlife Sanctuary, Bakuamari Stream, 454 ft [138.3 m], N 26° 21’18.5’’, E 90° 19’ 31.3’’, 4.vii.2011, coll. Bijita Barman.

Repository. The type specimens are deposited in the CEL, ZSI, New Alipore, Kolkata, West Bengal, India. Holotype Reg. No. 3319/H15 and paratypes Reg. No. 3320/H15 to 3321/H15.

Etymology. The name expositus is a Latin adjective meaning exposed and refers to the unusually exposed gonapophyses of the female.

Diagnosis. The female of Pleciobates expositus sp. nov. can easily be distinguished by the exposed gonapophyses ( Fig. 2G ); the sixth connexival segment bearing a long hairy process; a well developed, erected metanotal median tubercle, with an angulate tip ( Fig. 2C ); and the straight and wide posterior margin of abdominal sternite VII ( Fig. 2G ). The male of expositus sp. nov. can be distinguished from other species by the structure of the endosomal sclerites ( Figs. 2K, L ).

Description. Apterous male (holotype): ( Figs. 2A, D, E, H–L ). Body length 6.50; body width (across mesoacetabula) 1.63.

Colour. Dorsum of body dark brown to black except yellowish brown head (with a crown-shaped black mark in front of eyes), yellow median oblong, basally widened mark of pronotum and brown inner connexival margin; posterior region of acetabula and posterior region of abdominal segment VII to tip of abdomen yellowish brown. Venter pale yellowish brown except anterior three-fourths of mesosternum black (but with thin yellow anteromedian stripe), mesosternum one-fourth from posterior region with W-shaped angulated yellowish brown mark, prominent in alcohol. Eyes black. Antennae black, except bases dark brown. Rostrum yellowish brown except apex of third and whole fourth segment black. Legs: coxa and trochanter of all legs yellowish brown; forefemur yellow with two brown to black stripes; foretibia and foretarsus black; mid and hind legs black except yellowish brown bases of femora. Dorsum of body clothed with minute silvery white hairs, prominent on meso-, metanotal sulcations and abdominal tergites, more pronounced on median junctions between metasternum and first abdominal tergite and between first and second abdominal tergites.

Structural characters. Head length 0.99, maximum head width across eyes 1.05; minimum interocular width 0.42; eye length 0.49, eye width 0.26. Head apex slightly produced in dorsal aspect; antennal tubercle well developed. Dorsum of head with rows of few setae from base of antennal tubercle along inner eye margins to base of head. Rostrum not surpassing forecoxa. Lengths of antennal segments I–IV, 2.72, 0.64, 0.80, 0.70; first antennal segment more than 4.2 times as long as second and longer than combined length of remaining three segments. Base of first antennal segment at lower margin with one long and a few short setae; fourth antennal segment with evenly distributed, 2–4 short setose spines along the outer concavity; antennal segments II and III without setae.

Pronotum with anterior and posterior margin almost straight; pronotal length 0.56, pronotal width 1.09. Prosternal length 0.43, mesonotal length 1.95; mesosternal length 2.87, metanotal length 0.56; metasternal length 0.24. Meso- and metanota with median longitudinal sulcus, clothed with minute silvery white hairs.

Lengths of legs segments: foreleg: femur 2.83, tibia 2.08, tarsus I–II 0.72, 0.51; mid leg: femur 8.78, tibia 4.27, tarsus I–II 1.62, 0.32; hind leg: femur 7.90, tibia 1.78, tarsus I–II 0.11, 0.15. Forefemur width 0.37.

Foreleg: trochanter with eight long setae on ventral surface. Femur dorsally with two black stripes, one on the lower margin and another one about one fifth from anterior margin, both confluent near apex ( Fig. 2A ), ventrally without prominent stripe, apically margined with piceous hue. Flexor side of femur with 15 setose spines, apex with three minute spines in addition to fringe of setae. Apex of tibia angularly produced on flexor side, with prominent spine subapically, with few erect setae; anterior apical margin fringed with few procumbent setae. First tarsal segment basally with few procumbent hairs on anterior margin, with evenly distributed erect setae along entire inner margin. Second tarsal segment subapically with a few long setae along outer margin. Claws prominent. Mid leg: ventral region of right trochanter with one denticle and left with two denticles; posterior margin of femur from subbasal to beyond middle with short curved stout evenly distributed spines; posterior subapical margin of femur with two stout spines and three long curved setose spines, apex with two stout spines and fringed with long hairs; posterior margin of tibia fringed with long setae except basally, maximum hair length 0.29; inner margin of first tarsal segment at three–fifths from base with minute apically curved hairs, apex of second tarsal segment with one minute seta; claws absent. Hind leg: trochanter at posteroventral region with one thin short pale brown spine on right side, two on left side; inner margin of femur at one-fourth from base with five thin, erect hairs; apex of femur with few stout spines; tibia and first tarsal segment without any characteristic setae; separation between first and second tarsal segments distinct; second tarsal segment with two setae, one subapical and one apical; claws absent.

Abdomen: length 2.43; abdominal venter densely clothed with silvery white hairs; anterior margin of tergite I slightly convex and posterior margin slightly concave; abdominal tergite I with median longitudinal sulcus; separation between tergites I and II distinct; lengths of tergites I–IX, 0.23, 0.21, 0.16, 0.17, 0.18, 0.22, 0.55, 0.39, 0.32, combined length of tergites I–VII 1.69; posterior margin of tergite VII convex; between connexivum and abdominal tergites with longitudinal membranous area; posterior margin of sternum VII widely concave, connexivum slightly angularly produced posteriorly ( Figs. 2A, E ); anterior region of sternum VIII with transverse depression; lengths of sternite II–IX, 0.11, 0.12, 0.14, 0.15, 0.21, 0.33, 0.39, 0.81, combined length of sternites II–VII 1.07. Proctiger (= suranal plate) broad at base, suddenly narrowed beyond midlength to short posterior lobe, clothed with dense hairs ( Fig. 2J ). Pygophore with W-shaped median notch at base, its apical part produced into tongue-like lobe, clothed with minute hairs, pygophore length 0.89, width 0.64 (measured after dissection) ( Figs. 2H, I ). Paramere basally stout, curved before middle; outer margin beyond middle straight to slightly curved; apically with pilosity; tip round and slightly bent at middle ( Fig. 2D ); paramere visible externally at abdominal tip ( Figs. 2A, E ). Endosoma: dorsal sclerite deeply split anteriorly and basally, forming right and left sclerites; right dorsal sclerite reaching endosomal base, missing below, apex of dorsal sclerite forming C-shaped lobes, with outer lobe short and stout and inner lobe linear and elongated, in lateral view; left dorsal sclerite curved near base and fused with ventral sclerite; ventral sclerite broad, long, curved upward, beyond middle gradually tapered, subapically curved and surpassing dorsal and apical sclerites; ventral sclerites underlined by conjuctivum up to subapex; basal region of lateral sclerites less sclerotised, outer margin of lateral sclerites straight and subapex of inner margin bent inwards; saddle-shaped apical sclerite placed between apex of dorsal and ventral sclerites, much closer to dorsal sclerite than to ventral sclerite; paired ovate membranous lobes with two to three vein-like dark lines placed at apical part of endosoma ( Figs. 2K, L ).

Apterous female (paratypes). ( Figs. 2B, C, F, G, M ). Similar to holotype, with following exceptions (one female measured; range of all five specimens given in parentheses for some characters). Body length 7.47 (6.39–7.47), width at mesoacetabula 2.30 (2.11–2.30), head length 1.06, width at eyes 1.14, dorsal minimum width between eyes 0.45, eye length 0.50, eye width 0.33, antennal segments I–IV 2.55, 0.7, 0.73, 0.67; pronotal length 0.61, pronotal width 1.10, mesonotal length 1.92, mesosternal length 2.65, median yellowish brown hue intruded into darker portion from lower region wider than in male; metanotum with prominent tubercle, slightly erect with angulate tip, reaching posterior margin of abdominal tergite I, length of tubercle 0.26 (measured at lateral region), metanotal length 0.85 (measured along midline to tip of tubercle); metasternal length 0.24.

Legs. Lengths of leg segments: Foreleg, femur 2.73 (2.49–2.76), tibia 2.01 (1.85–2.25), tarsus I–II 0.77 (0.77–0.88), 0.6 (0.6–0.71); mid leg, femur 8.06 (7.63–8.44), tibia 4.3 (3.75–4.32), tarsus I–II 1.8 (1.22–1.8), 0.37 (0.25–0.37); hind leg, femur 7.32 (6.92–7.32), tibia 2.18 (2.08–2.2), tarsus I–II 0.09 (0.08–0.11), 0.13 (0.13–0.15). Forefemur width 0.26 (0.26–0.3). Length of hair fringe on mid tibia 0.23 (0.23–0.35); dorsal abdominal length 2.87 (measured from tip of metanotal tubercle to tip of abdomen), lengths of tergites I–IX, 0.25 (maximum length of tergite I), 0.28, 0.19, 0.21, 0.25, 0.49, 0.72, 0.39, 0.17, tergites VII–IX not compact, may be due to the projection of gonapophyses; combined length of tergites II–VI 1.45, anterior margin of abdominal tergite II convex; lengths of sternites II–VII, 0.12, 0.15, 0.21, 0.25, 0.54, 0.97, combined length of sternites V–VI 0.81; anterior width of sternum VII 1.47, posterior width of sternum VII 1.01; between abdominal sternites VI and VII with bare area, may be formed due to the loosely fitted genital segments and the projection of gonapophyses; posterior margin of sternum VII straight ( Fig. 2G ); connexival segment VI yellowish brown, with long tubular process clothed with numerous short hairs, connexival process length, left 0.94, right 0.97 (measured along inner margin), genital segments loosely fitted, connexival process reaching base of segment IX (except in one specimen in which the connexival process surpassing tip of abdomen, the genital segments partly retracted into abdominal segment VII, gonapophyses not projected, and the bare area between sternites VI and VII absent); posterior margin of tergites VI and VIII almost straight and posterior margin of tergite VII convex; posterior region of sternite VIII slightly bluntly produced laterally; proctiger (= segment IX) square to cylindrical; gonapophyses with brown sclerotised stripes prominent in lateral aspect, first gonapophysis with 13 long, erect setae basoventrally and with 31 medium-sized setae dispersed throughout ventral region, apically with thorn-like blunt process, length of gonapophysis process I (GP-I) 0.13; second gonapophysis clothed with setae, apically with thorn-like blunt process, length of gonapophysis process II (GP-II) 0.14; at middle between the paired processes (GP-II) with a small sclerite; GP-II stouter than GP-I, below GP-II, on apex of gonapophysis II with a pair of small sclerites (sl), fringed with short setae on outer margin, inner margin emarginated ( Fig. 2M ), length of the sclerite on apex of second gonapophysis 0.05; sclerites and processes on gonapophysis dark brown to black except tips of processes less sclerotised.

Distribution. Presently known only from the type locality in the Dhubri District of Assam, India ( Fig. 3 ).

Comparative notes. Pleciobates bengalensis sp. nov. and P. expositus sp. nov. differ from all other known species of Pleciobates by their elongate abdomens, most notably in females, but also recognizable in males by direct comparison of species. In females, at least the gonocoxae 1 (in P. bengalensis sp. nov.) or even the gonapophyses (usually in P. expositus sp. nov.) are exposed, whereas in species from southeastern Asia, these parts are completely withdrawn into abdominal segment VII. The colour of the dark body parts is dark brown to black (piceous) in the two Indian species, but black in other species. Moreover, the following additional differences were recognized: the posterior pronotal margin of the female is straight to slightly concave (bisinuate in other species); the first antennal segment, pronotum, fore and hind femora are relatively short; the metanotum is relatively long; the midline of the meso- and metanota bears a distinct longitudinal sulcation and pruinose mark (sulcation indistinct and no pruinose mark in other species); and the meso- and metanota are not convex (versus smoothly convex in other species). Based on these differences, it is suggested that the two new species are more closely related to each other than to the remaining Southeast Asian taxa.

Pleciobates bengalensis sp. nov. and P. expositus sp. nov. are rather similar to P. pacholatkoi from Vietnam and Thailand in regard to the straight posterior margin of the female sternum VII (see key, couplet 2), but distinctly differ in the metanotal tubercle, which is short in P. pacholatkoi and comparatively long and erect in P. bengalensis and P. expositus . The female connexivum is slender in P. expositus , but broad in P. bengalensis , and broad at base in P. pacholatkoi . The male connexivum is inwardly curved at midlength in P. bengalensis , while in P. expositus it is straight. The posterolateral corners of the basal part of the male pygophore are acutely angular in P. pacholatkoi in lateral aspect (see Chen et al. 2002 p. 206, fig. 42), but blunt in P. bengalensis and P. expositus ; in P. bengalensis they are arched ( Fig. 1H ) and in P. expositus they appear slightly angular with blunt tips ( Fig. 2H ). In lateral aspect, the lateral margin of the proctiger appears wavy in P. bengalensis (because the side corners are slightly curved ventrally), but simply angled in P. expositus (compare Figs. 1H and 2H ). The endosomal sclerites of the males are very similar to those of P. pacholatkoi . In P. bengalensis and P. expositus the ventral sclerite curves upward along the membranous lobe and reaches or surpasses the level of the anterior margin of the apical sclerite, whereas in P. pacholatkoi (see Chen et al. 2002 p. 209, fig. 51) it does not reach so far. The outer margin of the saddle-shaped apical sclerite is straight in P. pacholatkoi and P. bengalensis , but, sinuate in P. expositus ( Fig. 1H ), and its lower margin almost sigmoid in P. expositus and P. pacholatkoi , but concave in P. bengalensis .

Figures

FIGURES 2 A – M. Pleciobates expositus Jehamalar, Chandra and Zettel, new species (A, D, E, H – L: male; B, C, F, G, M: female): A and B, dorsal view; C, metanotum and abdomen, lateral view showing metanotal tubercle; D, left paramere, lateral view; E, abdominal segment VIII and genitalia, ventral view; F, abdominal tip, dorsal view showing connexival process, tergites VI – VIII, and proctiger; G, abdominal tip, ventral view showing exposed genitalia; H, genital capsule, lateral view; I, pygophore, ventral view; J, proctiger, dorsal view; K, endosoma, dorsal view; L, endosoma, lateral view showing sclerites; M, gonapophyses and proctiger, lateral (as—apical sclerite; ct—conjunctivum; ds—dorsal sclerite; G-I—first gonapophysis; G- II—second gonapophysis; GP-I—process of first gonapophysis; GP-II—process of second gonapophysis; ls—lateral sclerite; ml—membranous lobe; pr—proctiger; sd—seminal duct; sl—sclerite; vp—ventral projection; vs—ventral sclerite).

FIGURES 3 A – C. Distribution of new species of Pleciobates. A, India; B, marked area denoting Assam and West Bengal in Northeast India; C, records of Pleciobates bengalensis Jehamalar, Basu and Zettel, new species in Jalpaiguri, West Bengal (triangles) and of Pleciobates expositus Jehamalar, Chandra and Zettel, new species in Dhubri, Assam (circles).

FIGURES 1 A – M. Pleciobates bengalensis Jehamalar, Basu and Zettel, new species (A, D, E, H – L: male; B, C, F, G, M: female): A and B, dorsal view; C, metanotum and abdomen, lateral view showing metanotal tubercle; D, left paramere, lateral view; E, abdominal segment VIII and genitalia, ventral view; F, abdominal tip, dorsal view showing connexival process, tergites VI – VIII, and proctiger; G, abdominal tip, ventral view; H, genital capsule, lateral view; I, pygophore, ventral view; J, proctiger, dorsal view; K, endosoma, dorsal view; L, endosoma, lateral view showing sclerites; M, gonapophyses and proctiger, lateral view (as—apical sclerite; ct—conjunctivum; ds—dorsal sclerite; G-I—first gonapophysis; G-II—second gonapophysis; GP-I—process of first gonapophysis; GP-II—process of second gonapophysis; ls—lateral sclerite; ml—membranous lobe; pa—paramere; pr—proctiger; py—pygophore; sd—seminal duct; sl—sclerite; vp—ventral projection; vs—ventral sclerite).