Potamophilus kelabitensis, Kodada & Boukal & Vďačný & Goffová & Ondrejková, 2022

Kodada, Ján, Boukal, David S., Vďačný, Peter, Goffová, Katarína & Ondrejková, Kamila, 2022, Elmidae of Sarawak: the genus Potamophilus Germar, 1811, with a description of P. kelabitensis sp. nov. (Insecta: Coleoptera), European Journal of Taxonomy 806 (1), pp. 1-18 : 6-15

Potamophilus kelabitensis sp. nov.

urn:lsid:zoobank.org:act:D801EBA4-C36A-4569-B495-7792B4B58F9D

Figs 2–5

Type locality

Malaysia, Sarawak, Miri district, Ramudu. Adults were collected at light in the Pa’Kelapang river environment in the Ramudu settlement ( Fig. 5 ).

Diagnosis

Potamophilus kelabitensis sp. nov. is an elongated, parallel-sided, medium-sized (PEL: 5.3–7.3 mm), predominantly black species with reddish-brown antennal segments 1–4, distal portion of femora, trochanters, anterior face of mesofemora, and claws. The pronotum is about 1.5 × as wide as long, gradually expanded posteriad, widest in front of posterior margin, and deeply excised in hind angles. Pronotal sides are moderately arcuate, finely crenate, and explanate, on each side with conspicuous blunt tooth posteriorly; posterior angles are nearly rectangular. Pronotal surface bears dual punctuation. Large punctures are moderately larger than facets, nearly confluent or separated by distances up to 1.5× a puncture diameter, punctures appear to be denser laterally. Small punctures are intermixed within larger ones and are moderately larger than those on the head. Elytron with ten punctate striae and one accessory basal stria between the sutural and second stria. Strial punctures on the disc are more prominent than those on the pronotum, separated by one puncture diameter, punctures becoming smaller posteriorly; punctures in striae 6–10 are more prominent, appearing subquadrate and more closely arranged. Intervals are flat, finely punctured; sutural interval moderately raised; elytral apices are slightly deflected and not meeting at the suture, separated by a gap, narrowly rounded and not protruding. The aedeagus is trilobate, symmetrical; parameres in the apical portion are narrowed, flattened, abruptly bent ventrad, and less sclerotised; apices do not reach the apex of the penis.

Differential diagnosis

The new species differs from all other described species of Potamophilus by the following combination

of external characters:

– a relatively small size (separating it from P. feae );

– distinctly crenate lateral margins of the pronotum (separating it from P. acuminatus , P. albertisii , P. feae , P. papuanus , and P. spinicollis );

– deeply excised hind angles of the pronotum (separating it from P. albertisii );

– lack of impression on the pronotal disc in front of the scutellum (separating it from P. acuminatus and P. spinicollis );

– flat elytral intervals except the sutural one (separating it from P. acuminatus , P. feae , and P. spinicollis );

– coarse strial punctures on the elytra (separating it from P. albertisii );

– subquadrate and not rounded strial punctures in intervals 6–10 (separating it from P. acuminatus , P. feae , P. papuanus , and P. spinicollis );

– evenly rounded elytral apices in both sexes (separating it from P. acuminatus , P. albertisii , P. feae , and P. papuanus );

– the absence of a distinct, well-separated median tubercle on the meso- and metatibia in males (separating it from P. albertisii , P. feae , P. papuanus , and P. spinicollis ).

For the sake of convenience, brief diagnoses of the described species are given below.

In P. acuminatus (PEL: ca 6.1–7.7 mm), the hind angles of the pronotum are deeply excised, pronotal sides are smooth, not crenate; pronotal disc with a wide, distinct depression in front of the scutellum. Strial punctures on the elytra are moderately coarse, sharply impressed, rounded, and separated by about their diameter. Elytra are long and narrow (ca 3.6–4.0 × as long as pronotum), with the first interval raised in the posterior 0.8 of its length, distinctly convex intervals 3 and 5, and other intervals flat to feebly convex. The apex of each elytron is produced, angulate in males while acuminate and more protruding with divergent apices in females. Meso- and metatibia are weakly sinuous; mesotibia in males is usually more strongly enlarged distally with an indistinct median tubercle.

In P. albertisii (PEL: ca 6.8–7.1 mm), the hind angles of the pronotum are at most slightly emarginated, with the emargination at most half as wide as scutellum; pronotal sides are smooth, not crenate; pronotal disc is flat or at most indistinctly impressed in front of the scutellum. Strial punctures on the elytra are moderately fine to fine, conspicuously sharply impressed, elongate, and separated by about 1–2 × their length. The first elytral interval is raised, and the remaining intervals are flat or at most slightly convex, similarly as in P. kelabitensis sp. nov. The apex of each elytron is produced, angulate in males and acuminate in females, with subparallel apices. Meso- and metatibia are weakly sinuous, usually more strongly so and always with a distinct, acute median tubercle at the distal end of both tibiae in males.

In P. feae (PEL: ca 9.5–10.4 mm), the hind angles of the pronotum are deeply excised; pronotal sides are smooth, not crenate; pronotal disc is at most indistinctly impressed in front of the scutellum. Strial punctures on the elytra are moderately coarse, more delicate on the declivity, moderately sharply impressed and rounded, separated by about 1–2 × their diameter; first and third interval in the posterior half are distinctly raised, other intervals at most feebly convex. The apex of each elytron is produced, more or less angulate, the angle acute (ca 60°), with an almost identical shape in both sexes. Mesotibia is weakly sinuous, and the distal end bears a stout median tubercle in males; metatibia is almost straight in both sexes.

In P. papuanus (PEL: ca 5.4–5.9 mm), the hind angles of the pronotum are deeply excised; pronotal sides are smooth, not crenate; pronotal disc is evenly convex to flat in front of the scutellum. Pronotal disc is densely and finely punctate with the punctures smaller than the eye facets, i.e., the punctuation is finer than in P. kelabitensis sp. nov. Elytral intervals are more or less flat, and only the first interval is raised in about the posterior half; strial punctures are rounded, moderately large (slightly larger than eye facets), well and sharply impressed, separated by about 1–2 × their diameter. Elytral apices have an acute angle in males and are angulate to acuminate in females. Mesotibia and metatibia are distinctly curved/sinuate with a blunt tubercle on the mesal face of the distal part in males, nearly straight or only weakly sinuate in females.

In P. spinicollis (PEL: ca 7.0 mm), the hind angles of the pronotum are deeply excised; pronotal sides are smooth to indistinctly and irregularly crenate, especially in the posterior half; pronotal disc with a distinct subtriangular depression in front of the scutellum. Elytral intervals are convex on the disc, with the first interval raised in the posterior 0.8 of its length. Strial punctures are rounded and conspicuously coarse, larger than those on the pronotum and much larger than eye facets, well and sharply impressed, separated by at most their diameter on the disc, smaller and sparser towards the lateral sides and posterior declivity. Male with the apex of each elytron separately rounded (female unknown) and with a rather prominent, pointed tubercle on the mesal face of the distal part of meso- and metatibia.

Etymology

The species is named after the Kelabit Highlands, an isolated highland plateau in the interior of the Sarawak State ( Malaysia) and bordering the Kalimantan Province ( Indonesia).

Type material

Holotype MALAYSIA • ♂; “ Malaysia, Sarawak, Miri distr., Ramudu , 26.06.2018, (15) 3°33′17.0″ N 115°29′38.5″ E 921 m a.s.l., Pa’Kelapang riv. env., J. Kodada & D. Selnekovič lgt., at light ”; CFDS.

Paratypes MALAYSIA • 11 ♂♂, 7 ♀♀; same collection data as for holotype; CFDS, CKB • 1 ♀; “ Malaysia, Sarawak, Miri distr., Bario , 19.– 23.6.2018, Lian Labang Garden , at light, J. Kodada & D. Selnekovič lgt.”; CKB JK540 • 2 ♂♂, 2 ♀♀; “ Malaysia, Sabah, Batu Punggul Resort env., river in primary forest, 25.Vi. 1990 ”; NHMW .

Measurements (all values in mm)

PEL: ♂♂ 5.31–5.46 (5.39 ± 0.06, n = 11), ♀♀ 5.77–6.93 (6.18 ± 0.36, n = 7); PL: ♂♂ 1.31–1.36 (1.32 ± 0.03, n = 11), ♀♀ 1.46–1.51 (1.51 ± 0.07, n = 7); PW: ♂♂ 1.91–1.97 (1.97 ± 0.09, n = 11), ♀♀ 2.07–2.57 (2.24 ± 0.16, n = 7); EL: ♂♂ 4.09–4.19 (4.14 ± 0.04, n = 11), ♀♀ 4.39–5.30 (4.76 ± 0.28, n = 7); EW: ♂♂ 2.12–2.22 (2.18 ± 0.03, n = 11), ♀♀ 2.42–3.14 (2.61 ± 0.23, n = 7); HW: ♂♂ 1.21–1.26 (1.25 ± 0.03, n = 11), ♀♀ 1.31–1.51 (1.37 ± 0.06, n = 7); ID: ♂♂ 0.71–0.80 (0.76 ± 0.27, n = 11), ♀♀ 0.81–0.91 (0.84 ± 0.05, n = 7).

Description

Holotype

The description of the holotype is completed by figures of the holo- and paratype specimens ( Fig. 2 ). BODY ( Fig. 2A ). Elongated, about 2.5× as long as wide (PEL/EW), parallel-sided, and moderately convex. Length including head 5.90 mm, maximal width across elytra 2.1 mm. Overall colour black; antennal segments 1–4, ventral mouthparts, distal portion of femora, trochanters, anterior face of mesofemora, and claws reddish-brown. Vestiture consists of longer, more or less erect setae and short, strongly recumbent, hair-like setae. Longer setae acute, in narrow sockets; dorsal ones moderately dense, brownish. Ventral setae yellowish, denser on lateral portion of thorax, posterior and lateral portion of ventrites, mainly on ventrites 3–5 and on coxae and trochanters ( Fig. 2C ). Short setae in narrow sockets (micropunctures), moderately densely to densely arranged, especially ventrally very dense.

HEAD ( Fig. 2D ). Moderately wider than long, large (HW: 1.2 mm), moderately declined dorsally, arched laterally and flattened ventrally; slightly retracted into prothorax; frontoclypeal suture finely marked. Labrum transverse, lateral angles rounded, anterior margin feebly emarginated in middle; very dense yellowish setae in close rows along anterior margin and laterally; surface finely punctured, with numerous longer setae. Anterior margin of clypeus straight, bordered by a row of longer setae, clypeus moderately shorter than labrum. Frons without sublateral depressions, surface densely punctured, puncture diameter slightly larger than a facet diameter, punctures separated by 0.5–1.5 × puncture diameter; interstices shiny, with micropunctures. Eyes large and strongly protuberant (ID: 0.7 mm), nearly circular in lateral view, without interfacetal setae, dorsally surrounded by long conspicuous setae. Antennal insertions exposed from above, close to eye margin; subantennal groove vaguely indicated only, shallow and short. Genae without anterolateral process, with numerous longer setae anteriorly. Gula as wide as long, not in the same plane with mentum, with cavity surrounded by dense hair-like setae; gular sutures straight; submentum short, transverse, densely punctured. Cervical sclerites large, wide and strongly sclerotised. Antenna 11-segmented, serrate, reaching slightly behind anterior margin of pronotum. Scape half as long as ID, moderately curved; posterior face flattened, lacking setae. Pedicel 0.5 × as long as scape, both with conspicuously long, hair-like sensilla; combined length of antennomeres 3–11 moderately longer than combined length of previous antennomeres.Antennomeres 6–10 transverse and more tightly aligned than previous antennomeres. Length/width of antennomeres 1–11 (in mm) as follows: 0.36/0.16: 0.18/0.99: 0.12/0.09: 0.06/0.08: 0.08/0.09: 0.81/0.09: 0.06/0.09: 0.06/0.09: 0.06/0.09: 0.06/0.09: 0.08/0.08. Maxillary palpus four-segmented, shorter than ID; terminal palpomere short, apically enlarged and truncate, with large sensory field; palpomeres 2 and 3 subequal in length, widened distally, with numerous moderately long hair-like sensilla. Mentum flat, short and wide, setose, with sides subparallel; palpigers strongly sclerotised, free, and unfused mesally. Labial palpus three-segmented, half as long as maxillary palpus; first segment short; second segment longer, with short and long hair-like sensilla around apical margin; third segment slightly longer than preceding, with apical sensory field similar to that on maxillary palpus. Ligula short and wide, more strongly sclerotised mesally than anterolaterally; anterior angles rounded, produced laterad.

THORAX. Pronotum 1.47 × as broad as long, PW: 1.95 mm, PL: 1.30 mm, gradually expanded posteriad, widest in front of posterior angles and deeply excised in hind angles. Pronotal sides moderately arcuate, finely crenate and explanate, on each side with conspicuous blunt tooth (projection) posteriorly; posterior angles almost rectangular; anterior angles not protruding. Anterior margin straight, sides with collar-like thickening; posterior margin trisinuate. Disc moderately convex, with two small prescutellar foveae, strongly deflexed laterad and anteriad. Surface with dual punctuation; large punctures moderately larger than facets, nearly confluent or separated by distances up to 1.5 × puncture diameter, appear to be denser laterally. Small punctures moderately larger than those on head, intermixed within larger ones. Hypomeron with ventral outline trisinuate, deepest emargination at level of procoxae. Width of hypomeron subequal in middle third, moderately narrowed anteriad and posteriad; anterior depression for reception of antennal tip small. Prosternum in front of coxae very short, distinctly shorter than prosternal process, transverse and not concealing head in repose. Prosternal process about twice as long as wide, subtriangular, posterior half distinctly narrowed, sides raised; mesal portion with longitudinal keel. Procoxae transverse, countersunk; procoxal cavities open posteriorly, moderately widely separated; postcoxal projection absent. Mesoventrite moderately shorter than prosternal process, separated by sutures from surrounding sclerites, posterior angles more or less produced posteriad and overlapping metaventrite; mesoventrite divided by fine discrimen; groove for reception of prosternal process deep, present along entire length, posteriorly widened. Mesocoxae large and prominent, subglobular; mesally separated by distance twice as wide as procoxae. Scutellary shield (scutellum) small, subtriangular, as wide as long, sides arcuate. Metaventrite twice as long as mesoventrite; anterior edge of metaventrite not carinate between mesocoxal cavities, anterolateral portion flat; exposed portion of anepisternum 3 moderately wide and long. Metaventral disc convex on sides, with sizeable medial depression extending from anterior third to posterior margin and with small medial depression anteriorly; discrimen fine, present along entire length of metaventrite; metakatepisternal suture subtle, hardly visible; surface finely punctured. Metacoxae large, transverse, oblique, almost reaching elytra, separated from metaventrite by a suture, posteriorly excavate for reception of femora.

Elytra 4.05 mm long (EL) and 2.15 mm wide (EW), subparallel-sided, moderately convex; each elytron with ten punctate striae and one accessory basal stria between sutural and second stria. Strial punctures on disc moderately larger than those on pronotum, separated by ca distance of puncture diameter, punctures becoming smaller posteriorly; punctures in striae 6–10 larger, appearing subquadrate and more closely arranged; intervals flat, finely punctured; sutural interval moderately raised. Humeri rounded and prominent; lateral margin moderately explanate, inflected at level of metacoxae; anterior margin smooth; elytral apices slightly deflected and not meeting at suture, separated by a gap, narrowly rounded and simple. Epipleura strongly inflected at the level of metacoxae, their width subequal along entire length, oblique and received in deep grooves on meso- and metathorax; posteriorly relatively tightly fitted to abdomen. Hind wing large, darkly pigmented, fully developed. Legs nearly as long as elytra; femoral pubescence short; tibial groove shallow, present on ca distal 0.66. Tibiae moderately longer than femora, slightly curved, nearly straight; pro- and metatibiae with dense short pubescence; mesotibia flattened and lacking dense pubescence, extended and slightly bent at apex with a trace of tubercle. Tarsi fivesegmented, ca half as long as tibiae (except claws), pro- and metatarsi densely pubescent; claws simple, similar in form and angle of inclination.

ABDOMEN. Five strongly sclerotised ventrites present, all well separated by sutures; first three ventrites connate, remaining two separated by thin membrane, movable; ventrites moderately convex, shallowly depressed along midline; first ventrite not entirely divided by metacoxae, admedian carinae absent; lengths of ventrites 1–5 (in mm): 0.75: 0.50: 0.35: 0.30: 0.45. Intercoxal process wide, subtriangular, acute anteriorly; lateral margins moderately raised; fifth ventrite truncate posteriorly and shallowly emarginate in middle. Surface of ventrites finely punctured and densely setose; third and fourth ventrites bears conspicuous longer, narrowly spaced, flattened setae near posterior margin; numerous flattened setae also on central and apical portion of fifth ventrite. Male sternite VIII symmetrical, deeply emarginate posteriorly and with numerous dense, long setae; anterior median struts short and thin ( Fig. 4D ). Tergite VIII dark, well sclerotised, narrowly rounded posteriorly, with dual punctuation and setation. Male sternite IX asymmetrical, anterior median strut long; posterior portion well sclerotised, semitubular, surrounding phallobase; posterior edge shallowly emarginated ( Fig. 4C ).

AEDEAGUS.Trilobate, symmetrical ( Fig. 3A–B ), ca 1.30 mm long; phallobase including anterior projection ca 0.7 × as long as parameres, nearly tubular, lateral portions sclerotised, ventral and dorsal portions membranous. Parameres individually articulated with phallobase, dorsally fused near base, ventrally free along whole length; parameres narrowed, flattened, abruptly bent and less sclerotised in apical portion ( Fig. 3C ), apices do not reach the apex of penis. Penis symmetrical, basal portion expanded ventrally nearly in the form of a ʻbellʼ; dorsal portion flattened with lateral sides explanate in basal 0.6 and further gradually narrowed apicad, thus penis nearly round in cross-section, with apex bent ventrad; ventral sac membranous without fibula, corona present.

Female terminalia

Posterior margin of female sternite VIII widely rounded; surface with numerous long, dense dark setae ( Fig. 4E ); anterior margin with robust, subtriangular median strut, the latter subequal in length to posterior portion of sternite. Tergite VIII wider and widely rounded posteriorly; punctuation and setation similar to that of males. Posterior margin of fifth ventrite with a small sharp projection in middle. Ovipositor ca 2.9 mm long, slightly longer than terminal ventrite; valvifers long and robust, ca 2.5 × as long as coxite ( Fig. 4A ); longitudinal baculi wide and well sclerotised. Coxites (preterminal segments) short, widened in dorso-ventral direction; transverse baculi bar-like, distinct, well sclerotised. Coxites not divided by transverse line ventrally ( Fig. 4B ); distal portion short, narrow and expanded in dorso-ventral direction with a cluster of blunt peg-like sensilla around apex. Stylus very short and bearing small apical sensilla.

Secondary sexual dimorphism

Females ( Fig. 2B ) are on average longer and broader than males. Their abdominal intercoxal process and the disc of the second and third ventrite are slightly convex, in contrast to the moderately concave (depressed) surfaces in males. In females, the posterior margin of the fifth ventrite is moderately prolonged and pointed in the middle, while in males, it is truncated and shallowly emarginated. The apex of the mesotibia in males is expanded, slightly bent inwards and bears a slight tubercle trace, while it is straight and unexpanded in females.

Variability

Males vary in body length (PEL) from 5.31 to 5.46 mm, females from 5.77 to 6.93 mm. Compared to the holotype, the morphometric characters vary (see measurements above), and there is also minor variation in the pronotal and elytral punctuation. Pronotal sides are usually moderately arcuate, finely crenate and explanate, on each side with conspicuous blunt tooth posteriorly. The crenate portion varies from finely crenate to deeply crenate between individuals, and the size and form of the posterior teeth also vary from long and subacute, produced posteriad to short and nearly blunt. The teeth on the left and right side of the pronotum are asymmetrical in some specimens.

Distribution

The species is recorded from northern Sarawak and southern Sabah, although the distribution is probably wider across Borneo, given that the type specimens are fully winged and most likely possess excellent flight ability.

Figures

Fig. 2. Potamophilus kelabitensis sp. nov. A. Male holotype (CFDS), dorsal view, length from anterior margin of clypeus to elytral apex: 5.90 mm. B. Female paratype (CKB), dorsal view, length from anterior margin of clypeus to elytral apex: 7.31 mm. C. Male paratype (CKB), ventral view. D. Detail of the head, pronotum, and anterior portion of elytra, male paratype (CKB).

Fig. 3. Potamophilus kelabitensis sp. nov., aedeagus of holotype (CFDS). A. Ventral aspect. B. Dorsal aspect. C. Lateral aspect. Scale bar = 0.1 mm.

Fig. 4. Potamophilus kelabitensis sp. nov. A. Ovipositor, ventral aspect. B. Distal portion of ovipositor, ventral aspect. C. Male segment IX with the spiculum gastrale, ventral aspect. D. Male sternite VIII, ventral aspect. E. Female sternite VIII, ventral aspect. Scale bars = 0.1 mm; A = a; B–E = b. Specimens: A–B, E = female paratype (CKB); C–D = male holotype (CFDS).

Fig. 5. The Pa’Kelapang River at Ramudu near the locality where Potamophilus kelabitensis sp. nov. was collected.