Grouvellinus quest, Freitag, Hendrik, Pangantihon, Clister V. & Njunjic, Iva, 2018

Freitag, Hendrik, Pangantihon, Clister V. & Njunjic, Iva, 2018, Three new species of Grouvellinus Champion, 1923 from Maliau Basin, Sabah, Borneo, discovered by citizen scientists during the first Taxon Expedition (Insecta, Coleoptera, Elmidae), ZooKeys 754, pp. 1-21 : 6-8

Grouvellinus quest sp. n. Figures 3, 7, 8

Type locality.

Malaysia, Sabah (Eastern Borneo Island), Maliau Basin, Creek east of 'Nepenthes Camp’, ca. 4°44'57"N, 116°52'45"E, 1000 m a.s.l. (Fig. 12B).

Type material.

Holotype ♂ (BOR/COL): "MALAYSIA: Sabah: Maliau Basin: \ Creek E Nepenthes Camp; bottom rock, \ run; ca. 4°43'57"N, 116°52'45"E, ca. 1000m a.s.l. \ 01.X.2017, leg. I. Njunjić, P. Serail, C. de Groot (NepC3g)"; terminal parts of abdomen incl. aedeagus glued separately on entomological cards. Paratypes: 3 ♂, 4 ♀ (BOR/COL): same data as holotype; 3 ♂, 3 ♀ (BOR/COL) "MALAYSIA: Sabah: Maliau Basin: \ Giluk River; Cryptochorinae water plants, \ run; ca. 4°44'36"N, 116°52'21"E, ca. 980m a.s. \ l.01.X.2017, leg. I. Njunjić, H. Freitag, L. Seip, P. Piccoli (GilR2r)"; 1 ♂, 5 ♀, (BOR/COL) "MALAYSIA: Sabah: Maliau Basin: \ upstr. Giluk Falls; bottom rock, run; \ ca. 4°44'49"N, 116°52'38"E, ca. 950m a.s.l. \ 01.X.2017, leg. I. Njunjić, CV. Pangantihon, P. Serail (GilF3g)"; 1 ♂, 1 ♀ (NMW) "BRUNEI: Mt. Pagon \ 61 ARIF3 \ 4°20'35.8"N, 115°15'40.6"E \ 5.VI.2012 \ leg. K. Baker"; 5 ♂, 4 ♀ (NMW) "BRUNEI: Muara, Mukin Kilanas, \ Wasai Kendal Fall; sandy lowland creek; \ sec. forest; c.10m asl, c. 4°52'N, 114°53'E \ 15.6.1997 leg. Mendoza (3)".

Etymology.

The species epithet refers to the English noun ‘quest’ (search, aspiration) in reference to the intense search for riffle beetles at Maliau Basin which was a big quest for the citizen scientists involved in the project. Additionally, the new species is named for the Dutch popular science magazine QUEST of which journalist Paul Serail joined the first taxon expedition. The word is used as a noun in apposition.

Description.

Body elongate obovate, 1.5-1.8 mm long (CL), 0.73-0.85 mm wide (EW), 2.1 times as long as wide (CL/EW).

Dorsal colouration (Figs 3, 7A) predominantly black; tarsi, antennae, and maxillary palps reddish dark brown; pubescence yellow. Ventral side (Fig. 7B, C) reddish dark brown.

Head 0.35-0.37 mm wide (HW); ID 0.14-0.21 mm; partly retractable; frons, clypeus, and labrum sparsely pubescent, slightly denser laterally; punctures small and scattered; intervals flat, glabrous. Frontoclypeal suture almost straight. Eyes very slightly protruding. Antennae genus-typical, rarely exposed, usually semi-circularly folded around anterior eye margin.

Pronotum (Fig. 7A) 0.49-0.55 mm long (PL), 0.56-0.64 mm wide (PW), wider than long (PL/MW), widest posterior 0.25, distinctly narrower than elytra, anteriorly moderately attenuate; anterior margin distinctly convex; median carina absent, sublateral carinae present, but indistinct at posterior 0-0.2; oblique impression shallow, extending from mid lateral rim to posterior 0.2; laterobasal impression shallow; pronotal disc distinctly vaulted, very densely punctate; punctures small and shallowly impressed; setae moderately long, often broken off; anterior and anteriolateral portions sparsely punctate; interstices glabrous and flat; impressions and lateral margins rugose. Hypomeron rugose.

Prosternum (Fig. 7B) short; lateral portions with very dense, fine pubescence (plastron); median portion including process medially broadly impressed and glabrous; margins finely striate; prosternal process sub-pentagonal, much wider than long.

Scutellum (Fig. 7A) sub-cordiform, flat and glabrous.

Elytra (Figs 3, 7A) roundly elongate, strongly convex dorsally, 1.08-1.29 mm long (EL), ca. 1.4 times as long as wide (EL/EW), sub-parallel basal 0.1-0.5, apices separately rounded (in both sexes), with eight longitudinal, moderately to slightly impressed rows of punctures; punctures somewhat regularly arranged, much larger (1.5-2.5 times of intervals) and deeper impressed basally, very small (0.2-0.4 times of intervals) and more shallowly impressed apically; less regularly arranged in lateral rows; interstices rugose except for almost glabrous apical portion; intervals 3, 5, 7, 8 with crenulate carinae approx. from basal 0.05 to 0.75, particularly on 2nd interval distinctly elevated basal 0.1-0.3; carinate intervals 5 and 7 convergent basal 0.05-0.15; all carinae with row of yellowish pubescence; lateral elytral margin serrate.

Mesoventrite (Fig. 7B) with deep subtrapezoidal grooves behind procoxae, medially with pair of oval impressions in males, the latter more indistinct or lacking in females.

Metaventrite (Fig. 7B) with irregular impressions, except for almost glabrous disc with longitudinally impression along median suture; interstices on marginal portions somewhat irregularly micro-striate to micro-reticulate.

Abdominal ventrites (Fig. 7C). Ventrite 1 with pair of longitudinal carinae bordering glabrous disc; ventrites 1-2 glabrous medially; lateral portions of ventrites 1-2 and almost entire ventrites 4-5 densely covered with plastron and scattered moderately long setae (Fig. 7C); apex and lateral margins of ventrite 5 more densely pubescent.

Legs (Fig. 3) slightly shorter than body; hind leg longest; tibia longer than tarsus and femur in all legs; coxae, femora, and tibiae moderately densely covered with short adpressed setae; inner (ventral) edge of distal tibia and tarsomeres 1-4 with fringe of long trichoid setae and short spine-like setae; outer (dorsal) edge of all femora and tibiae with longitudinal row of spine-like setae (in both sexes); apex of tibiae with pair of apical spines (most conspicuous at hind tibia). Legs not conspicuously varying between male and female.

Aedeagus (Fig. 8A, B) 550-560 μm long, 130-150 μm wide. Phallobase slightly asymmetrical basally, reaching ca. basal 0.6 of total aedeagus length. Median lobe moderately slender, gradually tapered towards a sub-globularly expanded apex; sub-globular apex bent ventrad (lateral view). Ventral sac apically inflated internally densely stippled and with dense fringe of moderately short, thin and comparably delicate spines; few of those overreaching apical fringe. Parameres slightly shorter than median lobe, apically moderately truncate and slightly dilated ventrally (lateral view), moderately broad and evenly conical from insertion to apical 0.15 in lateral view, usually with more than 30 trichoid setae in apical half, most of them at inner face; most apical setae longest and inserted at outer surface.

Male sternite IX with median strut moderately long and almost rectangularly bent sub-distally; posterior portion entirely fringed with a broad, distinctly sclerotized margin; posterior margin rounded; paraprocts sub-equal in length, not reaching apical margin.

Ovipositor (Fig. 8C). Total length ca. 620 μm. Stylus ca. 45 μm long, slightly conical basad, very slightly bent outwards, with ca. six short sensilla. Coxite approx. half as long as entire ovipositor (ca. 300 μm), with scattered extremely short, acute setae (most densely near apex) and few apical, hook-like sensilla; distal portion medially very slender, 2.4 times as long as proximal portion, inner margin pubescent (rather inconspicuous). Valvifer almost as long as coxite (ca. 280 μm), caudal portion slightly sclerotized and with scattered, extremely short, acute setae; fibula almost straight.

Variability.

The paratypes from Brunei are among the smallest specimens within the given measurement ranges and have a somewhat smoother elytral surface with less impressed punctures and less elevated carinae; the aedeagus agrees well in the distinctive features (shape, size and setation of parameres; shape and size of median lobe), but the phallobase is slightly longer (0.67 of total aedeagus length), slightly slenderer and more ventrally bent basally. In specimens from either locality, elytra and pronotum are commonly incrusted with deposits making proper examination of the surface structure hardly possible.

Larva.

Unknown.

Differential diagnosis.

Grouvellinus quest sp. n. superficially resembles the Indonesian species G. aeneus (Grouvelle, 1896), but it is slightly larger (CL: 1.5-1.8 mm vs. total length 1.5-1.7 mm), black (vs. brown), and the pronotal disc is flat between punctures (vs. shagreened). Based on the only available undamaged male material of G. aeneus (see Jäch 1984; NMW: "Bali Baturiti D. Limnol. Exp.") that was, however, not determined with absolute certainty, there are distinct differences in their aedeagi: larger (550-560 μm long), with longer phallobase (> half total length) and with sub-globular, ventrally bent tip of the median lobe in G. quest sp. n. (vs. smaller (400 μm long), with shorter phallobase (<half total length) and regularly rounded tip of median lobe in G. aeneus ). G. quest sp. n. and all other new species treated in here can easily be distinguished from the only know Malaysian species G. bishopi by the absence of a median pronotal carina.

Distribution.

This species is known only from Borneo Island, namely the upper Maliau Basin in Sabah and two sites in Brunei (Fig. 11).