Ancyronyx sarawacensis Jaech , 1994

Kodada, Jan, Jaech, Manfred A., Freitag, Hendrik, Ciamporova-Zatovicova, Zuzana, Goffova, Katarina, Selnekovic, David & Jr, Fedor Ciampor, 2020, Ancyronyx clisteri, a new spider riffle beetle species from Borneo, redescription of A. sarawacensis Jaech including a description of the larva and new distribution data for A. procerus Jaech using DNA barcodes (Coleoptera, Elmidae), ZooKeys 912, pp. 25-64 : 25

Ancyronyx sarawacensis Jaech, 1994

Type locality

(Fig. 11C ). Small stream, ca 3 m wide, flowing through degraded primary forest above the village of Arur Dalan near Bario, ca 1000 m a.s.l., Kelabit Highlands, northern Sarawak, Borneo, Malaysia.

Material examined. Adults.

Holotype ♂ (NMW): "Malaysia, Sarawak 1993 Kelabit HL. Umg. Bario, 26.2., ca 1000 m leg. M. Jäch (14)". Paratypes (NMW, CKB): 1 ♀, 2 unsexed exs: "Malaysia, Sarawak 1993 Kelabit HL., 5 km E Bario Pa Ukat, 27.2., 1000 m leg. M. Jäch (15)"; 1 ♂, 1 ♀: "MALAYSIA, Sarawak 1993 Kelabit HL., 5 km E Bario Pa Ukat, 1.3., 1000 m leg. M. Jäch (17)"; 1 ♂, 5 unsexed exs: "Malaysia, Sarawak Mulu NP, Long Iman 4.3.1993 leg. M. Jäch (20)"; 4 ♂♂, 2 ♀♀, 8 unsexed exs: "Malaysia - Sarawak 40 km E Kapit III. 1994 leg J. Kodada / Rumah Ugap Ng marating Kapit Sut".

Additional material

(BOR/COL, CCB, CFDS, CFM, CKB, NMW, UBDM, RMNH). SARAWAK: 1 ♂: "Malaysia, Sarawak, Marudi distr., Gunung Mulu NP, 16.10.2018, (40) 04.0267N, 114.8234E, 55 m a.s.l., small stream, J. Kodada & D. Selnekovič lgt."; 1 ♂ [FZ1634, MK505407], 1 ♀ [38, MK505398], 1 ♂ [39, MK505401]: "Malaysia, Sarawak, Miri distr., Bario env., 20.06./24.06.2018, (7) 03.76665N, 115.45371E 1146 m a.s.l., Arur Takang, J. Kodada & D. Selnekovič lgt."; 1 ♂: "Malaysia, Sarawak, Miri distr., Bario env., 20.06.2018, (8) 03.76567N, 115.45215E 1121 m a.s.l., Arur Takang, J. Kodada & D. Selnekovič lgt."; 1 ♂ [FZ1641, MK505414], 1 ♀: "Malaysia, Sarawak, Miri distr., Ramudu env., 27.06.2018, (16) 03.56813N, 115.49488E 919 m a.s.l., Pa’Ngaruren riv., J. Kodada & D. Selnekovič lgt."; 1 ♂ [FZ1633, MK505406], 2 ♀♀: "Malaysia, Sarawak, Miri distr., Bario env., 19.06.2018, (6) 03.74350N, 115.43137E 1131 m a.s.l., Pa’Ramapoh, J. Kodada & D. Selnekovič lgt."; 1 ♂ [82, MK566773], 1 ♂ [83, MK566771], 9 ♂♂, 9 ♀♀: "Malaysia, Sarawak, Miri distr., Bario env., 5.10.2018, (33) 03.759617N, 115.440233E 1143 m a.s.l., Arur Dalan, J. Kodada & D. Selnekovič lgt.; 1 ♂, 1 ♀: "Malaysia, Sarawak, Miri distr., Bario env., 22.06.2018, (10) 03.76245N, 115.43778E 1167 m a.s.l., Arur Dalan, J. Kodada & D. Selnekovič lgt."; 7 ♂♂, 7 ♀♀: "Malaysia, Sarawak, Miri distr., Bario env., 21.06.2018, (9) 03.76894N, 115.44592E 1171 m a.s.l., Pa’Marario, J. Kodada & D. Selnekovič lgt."; 3 ♂♂, 4 ♀♀: "Malaysia, Sarawak, Miri distr., Ramudu env., 26.06.2018, (14) 03.54745N, 115.49052E 921 m a.s.l., Pa’Kasi riv., J. Kodada & D. Selnekovič lgt."; 1 ♂, 4 ♀♀: "Malaysia, Sarawak, Miri distr., Ramudu env., 28.06.2018, (18) 03.54745N, 115.49052E 921 m a.s.l., Pa’Kasi riv., J. Kodada & D. Selnekovič lgt."; 1 ♀ [FZ1642, MK505418], 1 ♂ [FZ1643, MK505415], 1 ♀: "Malaysia, Sarawak, Miri distr., Pa’Lungan, 30.06.2018, (20) 03.81132N, 115.50737E 1103 m a.s.l., Petarutun riv., J. Kodada & D. Selnekovič lgt."; 1 ♂ [FZ1635, MK505422]: "Malaysia, Sarawak, Miri distr., Pa’Ukat, 25.06.2018, (13) 03.77346N, 115.47572E 1118 m a.s.l., J. Kodada & D. Selnekovič lgt."; 1 ♂ [FZ1628, MK505420], 1 ♀ [9, MK505396], 1 ♂ [10, MK505409], 15 ♂♂, 14 ♀♀: "Malaysia, Sarawak, Kuching distr., Bayur riv. near Kampung Bayur, 20.10.2018, 1°14'42.33"N, 110°17'35.26"E 40 m a.s.l., J. Kodada & D. Selnekovič lgt."; 1 ♀ [FZ1645, MK505404], 1 ♂ [FZ1646, MK505397], 1 ♂ [35, MK505399], 1 ♀ [36, MK566772]: "Malaysia, Sarawak, Kuching distr., Kampong Jangkar env., 10.7.2018, (29) 01.65911N, 109.70829E 67 m a.s.l., J. Kodada & D. Selnekovič lgt."; 1 ♂ [FZ1636, MK505394]: "Malaysia, Sarawak, Miri distr., Ramudu env., 26.06.2018, (14) 03.54745N, 115.49052E 921 m a.s.l., Pa’Kasi riv., J. Kodada & D. Selnekovič lgt.". SABAH: 50 ♂♂, 46 ♀♀: "Malaysia, Sabah, (Borneo), Kuamut river env. near Kampung Pisang Pisang, 3.-4. VI. 1996, 14a: shaded stream in primary forest with submerged wood"; 12 ♂♂, 4 ♀♀: "Malaysia, Sabah, Kuamut river env. near Kampung Pisang Pisang, 3.-4. VII. 1996, 14b: ca 10 m wide tributary of Kuamut River in primary forest."; 2 ♂♂, 1 ♀: "Malaysia, Sabah, ca 7 km S Sapulut, Saupi riv. in primary forest, 15.5.2001, J.F. Kočiam leg."; 1 ex. (sex not examined) [FZ1651, MK505400]: "Malaysia, Sabah, Tawau Division (Kalabakan), 10.7.2018, (MY16-MAL40) 04.560750N, 117.158367E 210 m a.s.l., Čiampor & Čiamporová-Zaťovičová lgt."; 1 ♂, 2 ♀♀: "Malaysia: Sabah: Maliau Res. Center.: Belian trail; small Maliau R. tributary; bottom gravel, riffle; ca 4°44'15"N, 116°58'15"E, 220 m a.s.l., 27.Sep2017, leg. H. Freitag, C.V. Pangantihon, I. Njunjić et al. / Taxon Expeditions (MRC2c)M"; 2 ♀♀: "Malaysia: Sabah: Maliau Basin: Agatis River; subm. wood, run; ca 4°41'51"N, 116°54'30"E, 520 m a.s.l., 02.Oct2017, leg. C.V. Pangantihon & I. Njunjić / Taxon Expeditions (AgtR2f)M.". Brunei: 1 ♂, 1 ♀: "Brunei: Temburong, Belalong River tributary Sungai Sibut; W of Ashton Trail, root packs, run; 4°32'38"N, 115°08'51"E, 170 m asl.; leg. H. Freitag & W.C. Hayden / Taxon Expeditions 29.Sep2018 (SiCg)M"; 2 ♂♂, 2 ♀♀ [H39, LR735553]: "Brunei: Temburong; Belalong River near UBD field station 04°32'49"N, 115°09'30"E, ca 100 m asl.; primary forest; submerged wood in run; leg. Pangantihon / Taxon Expeditions 28.Sep2018 (BeR1f)M".

Diagnosis.

Ancyronyx sarawacensis is a moderately large, usually yellowish species with a pronounced variability of coloration and body size (Figs 3C, D , 4A-D ; Tabs 4 , 5 ). From the most similar A. clisteri sp. nov., A. sarawacensis differs mainly in: 1) anterior elytral portion with expanded yellowish area, much larger than in A. clisteri sp. nov.; 2) ovipositor with shorter and wider distal portion of coxite which is ca 1.5-1.6 × as long as wide near middle; 3) proximal portion of coxite subequal in length to distal portion; 4) longitudinal baculum of paraprocts ca 1.3-1.4 × as long as entire coxite length; 5) about 9% divergence of the partial mtDNA for cytochrome c oxidase subunit COI. In the direct comparison the apex of the penis appears to be wider and less pointed in A. sarawacensis .

Redescription of the holotype.

Body form moderately elongate; elytra moderately convex dorsally, shiny, with highest point in 0.45 of elytral length; BL: 1.45 mm, EW: 0.71 mm, BL/EW: 2.04.

Coloration (Fig. 3C ). Labrum, mouth parts, antennae, clypeus and anterior half of frons yellowish; remaining portions of cranium black; pronotum yellowish with large mesal black spot, spot narrowed near middle; scutellum brownish. Elytra with lateral margin and epipleura black along anterior half; dorsum extensively yellowish with six black spots: a small elongate sutural spot behind scutellum; a second, elongate narrow sutural spot on elytral declivity; two lateral, suboval spots extending within elytral striae 3-9 from anterior third slightly behind middle length of elytra; two subapical small spots within elytral striae 4-5. Mesanepisterna, metanepisterna, lateral portion of metaventrite and lateral portions of ventrite 1 black; coxae yellow; femora black on distal sixth, yellowish on remaining surface; tibiae dark in proximal half and near articulation with tarsi, yellowish in distal portion; tarsomeres 1-2 darker; tarsomeres 3-5 and claws yellowish.

Head. Labrum shorter than clypeus; anterior margin almost straight; surface with fine irregular punctation, finely setose. Clypeus wide, densely punctate; sides rounded. Frons and vertex densely, finely punctate, reticulate; reticulation more distinct on black portion of vertex; surface with narrow, elongate distinct granules; frontoclypeal suture almost straight, finely impressed. Eyes well protruding, with large facets, semicircular in outline; HW: 0.38 mm, ID: 0.20 mm. Antennae 11-segmented, 0.46 mm long, moderately longer than pronotum; ratio of length of antennomeres 1-11: 0.055: 0.061: 0.042: 0.030: 0.031: 0.030: 0.029: 0.029: 0.032: 0.037: 0.089 mm. Gena microsculptured; gula narrow, smooth; gular sutures indiscernible; posterior tentorial pits deep and large.

Thorax. Pronotum distinctly wider than long (PL/MW: 0.81), widest near middle; anteriorly attenuate; anterior margin strongly arcuate; most of hypomeral portion visible in dorsal view; anterior transverse groove deep, oblique, dividing pronotum; area anterior and posterior of transverse groove strongly gibbous; anterior mesal longitudinal carina absent; posterolateral oblique grooves strongly impressed (Fig. 6E, F ). Pronotal surface densely punctate and irregularly reticulate on disc, with flat cordiform granules mainly in lateral and anterior portion; granules rather irregularly spaced; anterior and posterior portion smooth; prescutellar pits round and deep; PL: 0.42 mm, MW: 0.52 mm. Prosternum densely and roughly punctate; anterior portion very short; prosternal process distinctly transverse, almost flat, slightly protruding posteriad; posterior margin widely rounded. Scutellum subpentagonal; surface smooth and moderately elevated. Elytra elongate; EL: 1.06 mm; sides slightly narrowed at ca anterior 0.4, then gradually convergent to rounded apices; each elytron with ten more or less regular rows of punctures; six rows between suture and shoulder; accessory scutellary rows absent (Fig. 6C ); punctures large, round and deeply impressed on disc and laterally, smaller and less distinct anteriorly and posteriorly; interstices and intervals wider and flat on disc, narrower and slightly convex laterally and posteriorly; surface shiny; humeri prominent. Mesoventrite almost flat, less than half as long as prosternum along midline; mesoventral cavity shallow and narrow; surface strongly and irregularly punctate; mesoventral discrimen invisible. Metaventrite along midline distinctly longer than combined length of prosternum and mesoventrite; anterior margin arcuate; disc with large mesal longitudinal depression; discrimen depressed; surface of disc glabrous, with fine, scarce punctures; large, deep irregular punctures along anterior margin and on lateral portions of metaventrite; punctures coarser and denser laterally (Fig. 6D ). Hind wings fully developed. Forelegs about 1.54 × as long as body length; claws large and robust, with one small subbasal and one hardly discernible, basal tooth.

Abdomen. Intercoxal process longer than length of ventrite 2, very wide, anteriorly widely arcuate, with rows of deep large punctures along anterior margin; ventrite 1 longest; ventrite 2 ca 0.75 × as long as ventrite 1; ventrite 3 ca 0.88 × as long as ventrite 2; ventrite 4 ca 0.75 × as long as ventrite 3; ventrite 5 ca as long as combined lengths of ventrites 3 and 4. Surface of ventrites 2-5 with sparse punctures and setigerous, flat, more or less cordiform granules; punctures more distinct on mesal portion, granules more prominent and more conspicuous laterally. Male sternite IX ca 340 μm long, asymmetrical; apical margin distinctly arcuately emarginated; lateroapical portion with short setae; paraprocts not reaching beyond apical margin. Tergite VIII finely reticulate, with conspicuous median transverse ridge separating posterior and anterior portion; basal half with microtrichial pattern; apical margin hyaline, with subapical fringe of hair-like setae; setae on sublateral portions stronger and longer than those along margin.

Aedeagus (Figs 15A, B , 16A, B ) ca 358 μm long; penis about 2.63 × as long as phallobase; sides subparallel from base to apical fourth then gradually tapering apicad; apical half moderately curved ventrad; dorsolateral portion only with few very short setae; apex narrowly rounded; lateral basal apophyses long; ventral sac large; fibula long and narrow; surface of endophallus with numerous almost regularly arranged, small spines; corona not discernible in endophallus repose. Entirely extruded endophallus more than twice as long as aedeagus, asymmetrical (description based on one specimen (CKB) from the type locality); most of the following characters of the endophallus, even if it is extruded, are difficult to observe and clearly visible in Fig. 10G : supporting sclerites of endophallus thin; ventral and dorsal bladders bulbous, extending less than half of penis length, with few very fine short thin setae; distal portion of endophallus tubular, very long; apex narrowed and supported by a fine elongate sclerite near gonopore (Fig. 10G ). Phallobase asymmetrical; parameres moderately exceeding midlength of penis, widest near base, narrowed to apex; dorsal and ventral margin sinuate; apex narrowed and rounded; outer surface of parameres with short setae.

Description of ovipositor

(Fig. 17A-C ). Ovipositor in females from the type locality ca 435 μm long; stylus (gonostylus) narrow, straight, about 0.7 × as long as distal portion of coxite. Coxite short and stout; posterolateral angle rounded, not protruding. Distal portion of coxite ca 1.5-1.6 × as long as wide, moderately bent; surface with numerous conspicuous peg-like/spine-like setae; apical area with few moderately long trichoid and few thinner peg-like setae; inner margin moderately pubescent. Proximal portion of coxite about as long as distal portion, with numerous stout peg-like and trichoid setae; transverse baculum well sclerotised; longitudinal baculum of paraprocts ca 1.3-1.4 × as long as coxite length.

Secondary sexual dimorphism.

Not strongly pronounced. On average, females are longer and wider than the males (Tabs 4 , 5 ). Females possess narrower and shallower longitudinal depression of the metaventrite, and their terminal ventrite is longer and narrower than in males. All these differences named here refer to syntopic specimens.

Variability.

In addition to the metric characters (Tabs 4 , 5 ), adults of Ancyronyx sarawacensis vary in color pattern, body form and surface structures. This is obviously dependent on altitude and water temperature. Specimens from the Kelabit Highlands usually exhibit a more extensively black cranium, their pronotal spot is usually not or less distinctly divided, the elytral spots are wide (Fig. 3D ). Generally, any fusion of elytral spots is rather rarely seen and if, then only the three posterior spots fuse. The elytral surface appears shinier and smoother; the anterior transverse pronotal groove is deep, and areas anterior and posterior of these grooves are strongly gibbous, and their body form appears generally shorter and more convex. In comparison, the specimens from Sarawak and Brunei lowlands (Gunung Mulu NP, Kapit area, Kampong Bayur, Kampong Jangkar, Temburong) usually have a paler cranium, and their pronotal spots are more distinct, smaller and isolated (Fig. 4B-D ). Furthermore, their elytral surface is less shiny, and their interstices are narrower, the pronotum is almost flat and the body appears overall slenderer. Specimens from Sabah uplands (Figs 3D , 4A ) tend to have darker heads and pronota and separately fused large anterior and posterior elytral spots, their color pattern is very similar to those of A. clisteri sp. nov. Pronota of these specimens are usually more convex, similar to those of the specimens from the Kelabit Highlands.

Material examined. Larva.

Nine larvae of three different sizes/instars including the larva used in the DNA analysis (CKB): "Malaysia, Sarawak, Miri distr., Bario env., 5.10.2018, (33) 3.759617N, 115.440233E 1143 m a.s.l., Arur Dalan, J. Kodada & D. Selnekovič lgt". For the description, the two largest larvae, probably representing last instars, were selected.

Matching of developmental stages.

All larvae were collected together with adults at the type locality. One larva [FZ1631, MK505395] was compared with adults of A. sarawacensis based on partial COI mtDNA sequences.

Diagnosis of mature larva

(Figs 7A , 8A , 9E-G , 10A-F, H ). Body elongate, tapered dorsad; length from anterior margin of head to apex of abdomen: 4.43 mm; largest width across metanotum: 1.01 mm; body ventrally almost flat, dorsally convex; dorsal sagittal line present from prothorax up to sixth abdominal segment (Fig. 7A ). Ratio of length of thoracic segments and abdominal segment IX: 0.60: 0.35: 0.32: 0.84 mm; lengths of all remaining abdominal segments between 0.21 and 0.26 mm. Thoracic segments II and III with flattened lateral tergal processes (Fig. 7B ); abdominal segments I-VIII with conical prominent bent lateral tergal processes (Figs 7A , 9I ). All spiracles small and subequal in form and size, biforous, situated at ends of prominent spiracular tubes on mesothorax and abdominal segments I-VIII (Figs 7A, B , 9I ). Dorsum densely covered with flat setiferous tubercles except for rugose distal portion of terminal segment (Fig. 7B ). Antennae and legs very short (Fig. 8A, B ). Prevailing ground color (Fig. 7A ) yellowish-brown combined with dark brown patterns on frons, adjacent portion of epicranium, posterior two thirds of pronotum; meso- and metanotum each with four pairs of dark brown signae (Fig. 7B ); genae very pale, almost white; abdominal segments I-VIII with two dorsolateral pairs of dark brown signae and with brownish spot near middle, dark coloration increasingly inconspicuous posteriorly (Fig. 7A ); segment IX pale brown on anterior portion, dark brown apically (Fig. 7A ). In contrast to previous darker patterns, anterior third of pronotum, dorsolateral portions of cranium, middle portion of abdominal segment IX as well as appendages and entire venter paler yellowish.

Head prognathous, partly retractable, distinctly narrower than pronotum (Fig. 9A ); maximum head width 0.55 mm. Labrum very short, ca 2.5 × as wide as long, separated from head capsule by complete suture, anterior margin arcuate, middle with transverse row of moderately long, ramified setae (Fig. 9B ); clypeus subequal in length with labrum, with a row of pilose setae along posterior margin; frontoclypeal suture complete. Anterior margin of frons arcuate, with a row of moderately long, pilose setae; anterolateral angles form short conical projections, each projection with one distinct peg-like pilose seta. Frontal arms broadly V-shaped, well impressed, epicranial stem absent (Fig. 7B ); surface of frons and adjacent area of epicranium with cordiform tubercles, which are distinct, flattened and provided with short scale-like setae (Fig. 9A ); anterolateral portion with one moderately long trichoid seta. Setal pattern on epicranial plates: one moderately long trichoid seta near dorsal margin of stemmata; one at 0.6 of cranial length near frontal arm; one ventral near antennal insertion; four long and very conspicuous trichoid setae on lateroventral portion; several simple spine-like setae on lateral/laterodorsal portion, mostly widely spaced, four of them arranged in an oblique laterodorsal row; genae with several spine-like slightly serrate/pilose setae on ventral portion. Antennae (Fig. 9C, D, G ) three-segmented, short, approximately 0.25 × as long as maximal head width. Scape (Fig. 9C, D ) elongate, moderately longer than wide, with three moderately ramified setae around distal margin (two trichoid setae of varying length and a single, moderately long, pointed peg-like seta); pedicel narrow, cylindrical and about 1.5 × as long as scape, distally with two minute peg-like setae (Fig. 9G ); flagellum and sensorium subequal in length, both elongate and about 4 × as long as wide; terminal segment with minute setae. Stemmata arranged in a single unified lateral spot, not exposed (Fig. 9A ). Mandibles (Fig. 13C ) short, distinctly longer than wide, left and right mandible almost symmetrical; apices wide, tridentate, ventral and dorsal teeth continuing in ventral and dorsal carina; right mola convex and prominent, left mola flat, asperities absent; articulated process setose, robust, half as long as mandible. Penicillus with moderately long, thin, setae, densely arranged in a row along mesal portion; outer mandibular edges arcuate, each bearing four conspicuous ramified setae; ventral condyles robust and prominent.

Ventral side of cranium (Fig. 9E ) with strong hypostomal ridge extending posteriad into robust hypostomal rods; the latter exceeding middle of cranium; oblique row of 3-5 short stout peg-like setae situated posteriad of hypostomal rods. Posterior tentorial pits small, gular sutures absent. Maxilla elongate, large, almost half as wide as mentum (across stipes); cardo very short, transverse, almost perpendicular to stipes. Stipes elongate, with several different setae (Fig. 9F ): one short ramified seta near base; four moderately long, extensively ramified setae in a submarginal row along anterior half; few conspicuous long trichoid setae on anterior fourth; palpifer well sclerotised, short and wider than palpomeres, apical portion with two spine-like setae. Maxillary palp three-segmented (Fig. 9E ), distinctly shorter than stipes width; palpomeres with a few short trichoid setae, terminal palpomere with several small peg-like sensilla. Galea undivided, elongate, about 2 × as long as wide; apex narrowed and rounded, with row of several moderately bent spines and numerous short, mesally directed setae; dorsal surface with cluster of dense thin setae. Lacinia subequal to galea in form and length; apex with dense, strong spines. Labium with very short and transverse submentum oriented vertically to mentum. Mentum (Fig. 9E ) about 1.6 × as long as wide; widest at anterior third; median portion shallowly impressed, laterally with row of six moderately long, extensively ramified setae in anterior 0.6 and a single moderately long trichoid seta at anterior third; anterolateral portion with one distinct stout peg-like seta on each side; disc of mentum with pair of mesal, longitudinal rows of five trichoid and ramified setae. Ligula with mesal longitudinal line, about as long as lacinia, with four short peg-like setae; anterior margin arcuate and densely setose; labial palp very short; apical segment similar to that of maxillary palp; palpiger undifferentiated.

Pronotum (Fig. 7A, B ) 1.5 × as wide as long; posterior half with seven pairs of partly fused small and rather inconspicuous areas (signa) with irregular polygonal reticulation (Fig. 9H ); three pairs of erected trichoid setae present on disc and one pair on posterolateral position; lateral margins fringed with long trichoid setae. Meso- and metanotum more than 3 × as wide as long, distinctly shorter than pronotum, each with five pairs of partly fused signa and one posterolateral and two admedian pairs of long erected trichoid setae; sides projected laterally, fringed with long setae; surface with tubercles. Posterior margins of all nota dentate, fringed with row of scale-like setae. Ventral side of prothorax with small triangular presternum (Fig. 8A ) and three hardly identifiable sclerites: one large anterolateral sclerite on each side and one small transverse sclerite on posteromesal portion; sclerites completely surrounding coxae, connate, more or less discernible in cleared specimen only. Ventral portions of both, meso- and metathorax, with six sclerites (Figs 8A , 10A ): two large anterior sclerites divided by fine line mesally; each side with one small anterolateral sclerite and one large lateral sclerite; the latter projecting moderately at posteromesal portion; anteromesal sclerites with rows of short spine-like setae along posterior margin. Legs (Figs 8A, B , 10A ) stout, five-segmented, about 0.5 × as long as thorax width, all similar in shape and length. Coxae large, distinctly wider than long, subellipsoidal; mesal portion moderately projecting ventrad; surface with a few short setae. Trochanters subconical, each with a single long trichoid seta on distal third. Femora subcylindrical with scattered short peg-like setae, most of them with serrate/setose margins (Fig. 10D, E ); largest setae concentrated on inner portion and around distal margins. Tibiotarsi subcylindrical, narrower than femora, subequal in length with trochanters and femora; surface with several different trichoid setae in distal portion and a pair of distinct, very closely set trichoid seta (Fig. 10B, C ). Pretarsi elongate, moderately bent, each with a single long trichoid seta.

Abdominal segments I-VIII similar in shape, each distinctly wider than long, sub-rectangular; sagittal line visible in segments I-VI; lateral tergal processes of segments I-VIII conical, prominent and bent with dorsally directed pointed tip (Figs 7A , 8A ); surface with asperities, stout setae and short spines; processes of subsequent segments moderately increase in size. Posterior margins of terga dentate and each fringed with scale-like setae. Ventral portion of segment I-VII with three well differentiated sclerites; median sclerite (sternite) of segment I widest, about 2.8 × as wide as a lateral sclerite (pleurite); sternites moderately narrowed posteriad, pleurites distinctly narrowed posteriad; pleurites of segments VIII-IX completely fused with tergites and sternites. Ventral surface with numerous stout short spines and several longer thinner trichoid setae; the latter concentrated on posterolateral portion; segments I-VIII with a pair of long, very closely set trichoid setae near basis of lateral process (Figs 9I , 10F ); posterior margins of segments dentate and fringed with scale-like setae. Terminal segment (Figs 7A, C , 10F ) 2.1 × as long as wide, widest at anterior 0.15, subconical; subtriangular in cross-section; apex narrowed. Dorsal surface with flat setiferous tubercles; the latter large and distinct on anterior two thirds, absent or inconspicuous on posterior third; setae on tubercles short; setae along lateral margins long and very distinct; several moderately long erect-trichoid setae intermixed within granules on admedian portion. Ventral side with scattered, short or moderately long trichoid setae. Operculum (Fig. 10F ) elongate, subtriangular, almost 2 × as long as wide, slightly impressed medially, rugose; lateral and apical margins with trichoid setae; internally inserted pair of hooks half as long as operculum (Fig. 7C ); each hook with two clusters of longitudinally arranged trichoid setae near base.

Variation between larval instars.

The pre-final instars are shorter (3.85 mm) with narrower head (HW: 0.43 mm) and exhibit more evenly brown color from the posterior pronotal portion up to the anterior portion of segment IX. The pale anterior portion on the pronotum extends up to half of the pronotal length. Segment IX is relatively slender and 2.3 × as long as wide vs. ratio 2.1 in the final instar. The triangular presternum is not yet clearly delimited.

Comparative remarks.

The body shape of the larva is typical for the Ancyronyx variegatus (Germar) species group. In this group, larvae were described for A. helgeschneideri Freitag & Jäch, A. procerus , A. schillhammeri Jäch and A. variegatus ( Brown 1972; Freitag and Balke 2011; Freitag 2013). In contrast to those of the A. patrolus species group, these larvae share the comparably large size, dorsoventrally depressed body, stout legs and prominent conical lateral tergal processes (posterolateral appendages). Ancyronyx sarawacensis closely resembles A. helgeschneideri (comp. Freitag and Balke 2011) in the yellowish-brown color, similar size (final instar HW 0.55 mm vs. 0.50 mm; body length 4.4 mm vs. 4.5 mm), relatively large spiracles, similar shape and distribution of setae, tubercles and asperities, similar proportions and color pattern of abdominal segment IX, arcuate sides of head, and presence of short anterolateral frontal projections and lack of a median frontal projection. Ancyronyx sarawacensis differs from A. helgeschneideri in the pale anterior third of pronotum (vs. pale anterior and lateral pronotal margins), labrum with transverse row of ramified setae (vs. tuberculate with rather inconspicuous ramified and trichoid setae), submentum relatively longer and slenderer (1.6 × as long as wide vs. 1.4 ×) and clearly delimited triangular presternum. Larvae of Ancyronyx procerus (comp. Freitag and Balke 2011) can be distinguished by head being almost as wide as pronotum with sides almost straight (vs. head distinctly narrower than pronotum with sides arcuate), presence of a median frontal projection and three prominent frontal projections (vs. short anterolateral frontal projections). Furthermore, A. sarawacensis larvae are relatively slenderer than those of A. procerus (final instar HW 0.55 mm vs. 0.62 mm, body length 4.4 mm vs. 3.7 mm) and dorsally more densely covered with larger tubercles.

Habitat.

The altitude of all collection sites ranges from 40-1200 m a.s.l; the species is described from a small stream near Arur Dalan in the Kelabit Highlands (1000-1200 m a.s.l.). It is an upper reach (epirhithron), ca 3 m wide, with boulders and cascades, flowing through degraded primary forest. Water quality is presumably very good since the stream serves as drinking water for the settlements. Current and bottom substrates are heterogeneous; the latter includes mineral and organic deposits. All Ancyronyx specimens were collected from submerged wood. The larvae were found together with adults hidden in fissures of the bark of a large, relatively fresh submerged tree branch fully covered with bark. Mountain streams in the Bario area ( Pa’Ramapoh, Arur Takang and Pa’Marario) have fewer boulders, fewer cascades and more submerged wood. The river at Pa’Ukat is ca 10 m wide, shallow, slowly flowing, entirely shaded, with stony and sandy substrates and numerous fallen trees. Forest streams near Ramudu, Pa’Ngaruren and Pa’Kasi are ca 4-7 m wide, slowly flowing and meandering, with stones, some cobbles and sand substrates, submerged woods, leaf packs and exposed roots. Specimens were collected mostly from submerged dead wood, however, a few specimens come also from submerged roots of tree or bamboo. The Petarutung River in Pa’Lungan is 7-10 m wide, shallow, meandering, with sandy bottom and represents the only reddish colored river where some specimens were found (water color is probably due to humic substances from a nearby peat swamp forest). Outside the Kelabit Highlands A. sarawacensis was collected in small lowland and upland forest streams, which are moderately wide, rather shallow, usually meandering and with sandy or stony substrates, always containing submerged logs, woody debris and leaf packs. The specimens were collected mainly, but not exclusively, in stream reaches with stronger currents. The most atypical stream inhabited by A. sarawacensis was a small, slowly flowing, very shallow, meandering creek in Gunung Mulu NP (55 m a.s.l.) with large amounts of accumulated leaves and a sandy bottom, with some gravel and a few submerged branches (Fig. 11B ); specimens were collected together with Ancyronyx pulcherrimus Kodada, Jäch & Čiampor and a new species of Okalia Kodada & Čiampor.

Syntopic taxa.

Usually, the same piece of submerged wood, especially larger pieces can be inhabited by several genera of Elmidae and Dryopidae . Ancyronyx sarawacensis was found with specimens of Graphelmis berbulu Čiampor, G. labralis Čiampor and G. mumini Čiampor at the type locality. From lowland and upland Sarawak and Sabah, the following species were found to be syntopic: Ancyronyx procerus , A. acaroides , A. pulcherrimus , Graphelmis gemuk Čiampor and several species belonging to the G. pict a and G. marshalli groups. Some species of Leptelmis Sharp as well as Stenomystax montanus Kodada, Jäch & Čiampor, S. depressus Kodada, Jäch & Čiampor and S. minutus Kodada, Jäch & Čiampor and some species of Elmomorphus Sharp were also found syntopic.

Distribution.

This species is widely distributed in northern Borneo (Sarawak, Sabah and Brunei). In Sarawak it was collected in several small tributaries of the Dapur and the Kelapang rivers in the Kelabit Highlands; small tributaries of the Tutoh and the Melinau Paku rivers in and near the Gunung Mulu National Park; tributaries of the Sut River near Kapit, the Jangkar River near Lundu and a small stream near Kampung Bayur (Kuching area). In Sabah, it is known from the tributaries of Sapulut River near Batu Punggul; small tributaries of the Kuamut River as well as the Agatis River and a small tributary of the Maliau River. In Brunei, the species was collected from the Belalong River and from one of its small tributaries.

Figures

Figure 3. Habitus of: A Ancyronyx clisteri sp. nov., holotype B A. clisteri sp. nov., female paratype from Gunung Mulu NP, Sarawak C A. sarawacensis, holotype D A. sarawacensis, male from a tributary of Kuamut River " (14 a) ", Sabah.

Figure 4. Habitus of: A Ancyronyx sarawacensis, male from the tributary of Kuamut River " (14 a) ", Sabah B A. sarawacensis, male paratype from Kapit area, Sarawak C A. sarawacensis, female paratype from Gunung Mulu NP, Sarawak D A. sarawacensis, female from Bayur River near Kampung Bayur, Sarawak.

Figure 6. SEM micrographs: A, B Ancyronyx clisteri sp. nov. (male paratype from the type locality) C-F A. sarawacensis (female from the type locality). A Elytra and scutellum, anterior portion, dorsal view B same, detail of elytral surface, dorsal view C habitus, dorsal view D same, ventral view E head, pronotum and anterior portion of elytra, dorsal view F pronotum with reticulate surface structure, dorsal view.

Figure 7. Ancyronyx sarawacensis, larvae from the type locality: A final instar, dorsal view B pre-final instar, cleared specimen mounted on microscopic slide, detail of anterior portion, dorsal view C same specimen, terminal abdominal segment showing hooks of operculum, ventral view.

Figure 8. Ancyronyx sarawacensis, larvae from the type locality, SEM micrographs: A final instar, ventral view B pre-final instar, lateral view.

Figure 9. Ancyronyx sarawacensis, larvae (pre-final instar) from the type locality, SEM micrographs and cleared microscopic slide mounts: A head, frontal view B labrum, frontal view C left antenna, frontal view D right antenna, in rotaded view E final instar, head, ventral view F detail of ramified setae on anterior portion of stipes, ventral view G antenna, ventral view H detail of surface structure of prothorax, dorsal view I lateral portion of abdominal segments VI and VII, ventral view.

Figure 10. Ancyronyx sarawacensis A-F, H final instar larvae from the type locality, SEM micrographs and cleared microscopic slide mounts, G everted endophallus: A meso- and metathorax with legs, ventral view B right middle leg, detail, ventral view C detail of twin setae on tibiotarsus, ventral view D detail of pilose setae on femur, ventral view E detail of twin setae on pleurite VI, ventral view F terminal abdominal segment, ventral view G extruded endophallus, dorsolateral view. Abbreviations: Ds: dorsal sac-supporting sclerite, Vb: ventral bladder, Db: dorsal bladder, DpE: distal portion of endophallus, As: apical sclerite (according to Hayashi and Yoshitomi 2015).

Figure 11. Habitats of Ancyronyx clisteri sp. nov. and A. sarawacensis: A type locality of A. clisteri sp. nov., tributary of the Kuamut River near Kampung Pisang Pisang, Sabah B atypical locality of A. sarawacensis, shaded shallow stream in primary forest, Gunung Mulu NP, Sarawak C type locality of A. sarawacensis, small stream above Arur Dalan near Bario, Kelabit Highlands, Sarawak.

Figure 13. A Ancyronyx clisteri sp. nov., aedeagus of holotype with endophallus partly extruded, ventral view B same, lateral view C A. sarawacensis, larval mandible, ventral view.

Figure 15. Ancyronyx sarawacensis, specimen from the type locality: A aedeagus with endophallus partly extruded, ventral view B same, lateral view.

Figure 16. Ancyronyx sarawacensis, holotype: A aedeagus, ventral view B same, lateral view.

Figure 17. Ancyronyx sarawacensis: A ovipositor and abdominal segment VIII, specimen from a tributary of Kuamut River, Sabah " (14 B) ", ventral view B ovipositor, paratype from Kapit area, Sarawak, ventral view C ovipositor, paratype from the Kelabit Highlands, Sarawak, ventral view.