Scarodytes costatus, Aykut & Fery, 2017

Aykut, Medeni & Fery, Hans, 2017, Scarodytes costatus nov. sp. from the Bingöl Province in Turkey, the first species of the genus with costate elytra (Insecta: Coleoptera: Dytiscidae: Deronectina), Linzer biologische Beiträge 49 (1), pp. 395-414 : 397-401

Scarodytes costatus nov.sp.

T y p e l o c a l i t y: Turkey, Bingöl province, Solhan District, N Hazarşah village, ca. 1740 m, 39.020N 40.890E. The brook, in the rest pools of which the specimens have been found, is called "Hazarşah brook" (in Google Map given as "Hazaryah Deresi").

T y p e m a t e r i a l:H o l o t y p e: Ƌ, " 20.8.2014 Turkey, Bingöl prov. /ca. 10 km N Bingöl- Solhan road/N Hazarşah village/rest pools of brook, 1740 m / 39.020N 40.890E, M. Aykut leg." [printed], " Holotype / Scarodytes costatus nov.sp. / Aykut & Fery det. 2017" [red, printed] ( NMW). N o t e s: The holotype is slightly damaged on the right side of the pronotal disc, lacks the last antennomere of the left antenna and the inner metatarsal claw ; the left mid-leg is disarticulated; the last abdominal ventrite was removed from the rest of the abdomen for studying the aedeagus; abdomen and aedeagus are glued onto the card behind the specimen.

P a r a t y p e: 1♀, same label data as holotype, except red paratype label ; the paratype lacks the last nine antennomeres of the right antennae ( CHF) .

D e s c r i p t i o n o f h o l o t y p e:

H a b i t u s elongate oval, elytra appearing strongly vaulted due to high costae ( Figs 1 , 2 ; for comparison S. halensis in Fig. 4 and Nebrioporus carinatus (AUBÉ, 1838) in Fig. 5 ); sides of elytra evenly rounded; maximum width near midlength of elytra. Pronotum widest at base, here slightly broader than elytra at shoulders; thus body outline with weak discontinuity at shoulders. Dorsal surface brownish yellow to large extent with large brownish dots on pronotum and very indistinct vittae on elytra; surface appearing silky shining, almost matt due to dense punctation and/or reticulation. Ventral surface black to large extent, rather shiny in part; appendages brownish yellow.

D o r s a l s u r f a c e: H e a d: Anterior margin of head truncate, not indented; clypeus almost trapezoidal; generally brownish yellow; anterior margin of clypeus, clypeal grooves and near eyes diffusely brownish; vertex blackish brown; entire surface distinctly reticulate, rather matt; meshes small, polygonal, near anterior margin transversely shaped; punctation double and rather dense; diameter of smaller punctures that of one mesh, diameter of larger punctures that of two meshes; near anterior margin of clypeus larger punctures very sparse, becoming denser towards vertex; distance between larger punctures more or less that of diameter of two or three meshes, somewhat larger on centre of frons; smaller punctures becoming less dense posteriad; clypeal grooves very distinct and large; grooves and impressed stripe beside inner margin of eyes with dense larger punctures and stronger impressed reticulation; setae on head absent.

P r o n o t u m:Maximumwidthatbase,margininposteriortwothirdsalmoststraight, converging forwards, rounded in anterior third; posterior angles slightly acute, because somewhat protruded backwards; thus base of pronotum sinuate; lateral rim distinct, but disappearing short before anterior angle; sublateral depression parallel to lateral margins deeply impressed in posterior half, especially deep at base; however, pronotum without sublateral crease. Centre of disk with very deeply impressed longitudinal groove.

Pronotum brownish yellow like head, left and right of centre with large diffusely delimited brownish dot, extending until sublateral depression; near lateral and posterior margins brownish, lateral rim dark brown; at anterior margin blackish brown vertex of head translucent. Distinct reticulation only present near margins and before central groove, elsewhere only traces of reticulation perceptible. Punctation simple and more or less even, denser than on head, denser still in lateral and central depressions; punctures with diameter like that of larger ones on head. Very few setae present near side margins.

E l y t r a: Each elytron with four costae, inner (= first) one especially high, running from shortly behind anterior to shortly before posterior margin; second costa very indistinct and short, present only in anterior elytral half; third costa distinct, but weaker than first one, running from shortly behind anterior margin and ending far before elytral hind margin; sublaterally with fourth costa, weaker than third, starting behind first elytral quarter and running parallel to margin (and thus curved) almost until elytral apex. Sides of elytra slightly concavely sinuate preapically and apex indistinctly pointed.

Entire surface of elytra densely and evenly punctured; punctures slightly smaller than those on pronotum and denser; distance between punctures mostly smaller than their diameter; reticulation actually absent, only sporadic traces recognisable. Spaces between punctures smooth and shiny, but overall elytra appearing rather matt due to dense punctation. Punctation less dense on costae, these thus appearing somewhat less matt and standing out from rest of surface. Sutural puncture line very distinct, slightly impressed; base of elytra with short, curved line of deeply impressed punctures starting between suture and sutural line and running anteriorly parallel to base until interspace between first and second costa; no further puncture lines present on elytra. Margin of elytra with thin rim until shortly before apex. When viewed perpendicularly, elytral margin only perceptible immediately behind shoulders and near apex, due to sides of elytra projecting over margin and obscuring it. In lateral view side margin moderately ascending to shoulders; epipleuron visible until shoulders.

Elytra brownish yellow, somewhat lighter than head and pronotum; lateral rim slightly more brownish. Costae somewhat lighter than interspaces between them. At first glance elytra appearing non-vittate, but when carefully inspected diffusely delimited light brownish longitudinal vittae recognisable: one vitta between sutural line and first costa, starting somewhat behind base and running as far as end of first costa; a short very weak further vitta indicated in anterior fourth of elytra between first and second costa; fourth costa at midlength also with short vitta. Suture, sutural line and curved short line near base shining through dark brownish. Setae on elytra very short and sparse, present especially near side margins and in posterior fourth, but only recognisable if adequately illuminated.

V e n t r a l s u r f a c e: C o l o u r: Predominantly black; prosternum medially black, laterally brownish, but head black translucent; mouthparts and legs brownish yellow; gula, genae in part, prosternal process, propleuron and posterior third of metacoxal processes dark brownish; hypomeron (= pronotal epipleuron) and elytral epipleuron brownish yellow; first abdominal ventrite totally, second ventrite laterally and third to fifth ventrite laterally and posteriorly dark brown. Last ventrite dark brownish to large extent. Antennae brownish yellow, tenth antennomere distally very weakly darkened, eleventh more distinctly darkened in distal half. Last labial and maxillary palpomeres also darkened distally.

H e a d: Underside of head with gula smooth and very shiny, laterally and medially with some punctures. Genae with crease behind eyes, but only laterally distinctly engraved, more medially somewhat irregularly shaped; before crease surface mainly smooth and shiny, but more medially with weak reticulation; behind crease surface reticulate; some strong wrinkles present between eyes and mouthparts. Third antennomere distinctly shorter than second, fourth longer than third, but shorter than second; fifth to tenth as long as fifth, eleventh again longer.

P r o t h o r a x: Prosternum anteromedially (before procoxae) strongly vaulted and very coarsely sculptured; laterally (before propleuron) smooth and shiny, with very few punctures. Hypomeron latero-anteriorly flattened to a more or less triangular flat part; this part provided with some punctures; hypomeron else in large part smooth and shiny, posteriad with weak reticulation and some punctures.

Prosternal column (declivitous part of prosternum between procoxae, before prosternal process; sometimes treated as belonging to prosternal process) moderately ascending posteriad (as viewed in beetle turned upside down), between procoxae with indistinct protuberance near anterior part of procoxae. Prosternal process weakly inclined; broadly lanceolate, weakly costate longitudinally, in cross-section more or less roof-like, laterally very weakly impressed, lateral rim narrow; prosternal column and process covered with coarse punctures, between punctures surface smooth and shiny. Tip of process shortly rounded, reaching between mesocoxae and until anteromedial process of metaventrite.

P t e r o t h o r a x: Mesepimeron and mesepisternum mostly smooth and shiny, but nevertheless some very small punctures and extremely weakly impressed reticulation on parts of their surfaces, perceptible at high magnification. Metepisternum triangular ( Fig. 6 ), covered with obliquely stretched punctures, surface between punctures smooth and shiny. Lateral planes of "mesoventral column" parallel ( Figs 13 , 15 ; see separate section on this structure below). Anteromedial process of metaventrite rather narrow (ca. 1/3 of maximum width of mesofemur), reaching almost until middle of mesocoxae; distally with very short depression for reception of prosternal process.

Lateral part of metaventral wings very narrow and strongly curved backwards ( Fig. 6 ). Metacoxal lines diverging anteriad, becoming indistinct before hind margin of metaventrite. Hind margin of metacoxal processes obliquely incised; interlaminary bridge shortly visible ( Fig. 11 ), but not as fully exposed as in species of Deronectes ; bridge step-like, transformed into a more or less triangular (or wing-like shaped) elevation on second abdominal ventrite. Metaventrite and metacoxal plates densely covered with large punctures ( Fig. 6 ; for comparison Scarodytes fuscitarsis (AUBÉ, 1838) in Fig. 7 , S. halensis in Fig. 8 and Nebrioporus carinatus in Fig. 9 ); punctation somewhat denser on metacoxal plates; centre of each puncture situated in a conical pit, sides steeper anteriorly than posteriorly, most pits more weakly delimited posteriorly than anteriorly, pit around centre of each puncture smooth and shiny; surface between punctures also smooth and shiny; thus, entire surface rather shiny and not appearing matt ( Fig. 6 ). Metaventrite with small impunctate area left and right of midline and with impunctate rhomboidal smooth area medially before hind margin. Anterior and posterior margin of metacoxal plates impunctate and smooth, surface of plates near lobes of metacoxal processes largely impunctate and smooth, more laterally weakly reticulate. Metacoxal processes covered with smaller and denser punctures, less dense near apex and on lobes; shiny between punctures, but here nevertheless very weakly reticulate.

E l y t r a: Elytral epipleura anteriorly rather broad (broader than mesotibiae), more or less abruptly becoming narrower at level of first abdominal ventrite; epipleura punctured more or less like dorsal surface of elytra. Sublateral carina on ventral side of elytra distinct, and elevated before elytral apex, but without ligula.

A b d o m e n: First three ventrites rigidly connected. First abdominal ventrite punctured like metacoxal plates, second ventrite laterally with punctation denser, but becoming sparser lateromedially and almost absent medially (behind hind-margin of metacoxal processes); punctures on third to fifth ventrites somewhat smaller and generally denser, right and left middle slightly sparser. Last abdominal ventrite almost triangular, very weakly depressed subapically; apex rounded, but rim of ventrite very weakly pointed; very coarsely punctured, thus surface strongly and roughly structured. Entire abdomen without reticulation.

L e g s more or less simple; protibiae not conspicuously broadened distally. Metafemora with irregular puncture line in distal half along midline, before and behind with only few punctures; more proximally punctation becoming less sparse and puncture line no longer recognisable. Anterior face of metatibiae almost impunctate, but with a few setiferous punctures proximally and near ventral margin.

Protarsal claws distinctly prolonged; anterior claw weakly and evenly curved, somewhat more curved near end; posterior claw strongly curved at base, then almost straight and distally curved again. First three protarsomeres broadened, more or less as long as broad; ventral surfaces with some simple setae (no suckers). Fifth protarsomere rather short, and thick, much shorter than claws and not much longer than third protarsomere; midline on ventral surface with three spines. Mesotarsomeres not broadened, first three ventrally with a few simple setae and fifth on ventral surface with three spines along midline; claws slightly prolonged, weakly curved, more so near end. First metatarsomere slightly more than twice as long as second, as long as second and third together; fifth tarsomere about 1.5x as long as fourth; claws subequal, anterior claw slightly shorter.

S e t a t i o n: Prosternum medially and prosternal process with some setae; metaventrite medially and behind mesocoxae with very few setae; setae on metacoxal processes more numerous; setae very sparse on first and second abdominal ventrites; other ventrites with many setae; each of third to fifth ventrites with tuft of very long setae medially.

A e d e a g u s: Median lobe weakly and evenly tapering to apex in ventral view ( Fig. 18 ), apex very broadly rounded; lateral view as in Fig. 19 ; left paramere as in Fig. 20 .

Fe m a l e (paratype): genitalia not studied; specimen deviating from male in several characters:

- maximum width of pronotum somewhat before posterior angles, sides more rounded over entire length, posterior angles not acute, but slightly obtuse; thus discontinuity of body outline at shoulders more distinct ( Fig. 3 );

- pronotal and elytral pattern more developed, several longitudinal brownish vittae perceptible ( Fig. 3 );

- first elytral costa medially stronger raised, second and third costae less prominent; short "costa" between first and second costa actually not perceptible;

- entire surface of pronotum and elytra provided with dense short setae and reticulate between punctures; thus upper surface appearing more matt than in male holotype;

- postocular crease on ventral surface of head rather sharp over entire length, more strongly reticulate behind and also with some meshes before;

- distal darkening of antennae beginning already at eighth antennomere;

- protibiae narrower and longer than in male;

- first three protarsomeres not broadened; fifth tarsomere narrower and longer, almost as long as tarsomeres two and three together, with only two spines along

midline on ventral surface; protarsal claw not prolonged, somewhat shorter than mesotarsal claws;

- metaventrite with very weakly impressed reticulation between punctures; metacoxal plates with more distinct reticulation between punctures; thus, venter somewhat less shiny than in males;

- abdomen between punctures reticulate;

- last abdominal ventrite more depressed before apex; apex less broadly rounded, rim more pointed and slightly curved upwards.

M e a s u r e m e n t s: Holotype: TL = 4.1 mm, TL-h = 3.6 mm, MW = 2.15 mm; TL/ MW = 1.86; TL-h/ MW = 1.67; female paratype: TL = 4.3 mm, TL-h = 3.8 mm, MW = 2.25 mm; TL/ MW = 1.91; TL-h/ MW = 1.68.

D i f f e r e n t i a l d i a g n o s i s: Here we give only the most important differences of S. costatus nov.sp. (firstly) to other species of the genus (after the dash):

- strong costae on elytra – elytra without costae or swellings;

- elytral vittae strongly reduced and very diffusely delimited – vittae well extended and delimited;

- posterior angles of pronotum slightly acute and protruded backwards in male – posterior pronotal angles shortly rounded and not protruded backwards;

- interlaminary bridge weakly exposed – bridge fully concealed;

- punctures on metaventrite and metacoxal plates large and posteriorly very weakly delimited – punctures smaller and more distinctly delimited (although punctures in S. fuscitarsis also rather large; see Fig. 7 );

- interspaces between punctures on metaventrite and metacoxal plates reticulate in female – interspaces smooth (although traces of such reticulation observed also in some females of other species);

- rather irregular puncture line along midline of metafemora distinct only in distal third, proximally concealed by punctation before and behind – puncture line more regular and distinct over almost entire length;

- fifth protarsomere in male shorter than in female – differences not present or subtle.

D i s t r i b u t i o n: Known so far only from the type locality in eastern Turkey, Bingöl province, N Hazarşah village. This village is situated about 35 km NE Bingöl and about 15 km W Solhan.

E c o l o g y: The holo- and the paratype have been collected in two residual pools ( Figs 21, 22 ) of a brook which has much water and very strong flow in early spring, but is dry in summer. It is engraved in the rocky mountainous landscape, its bottom is sandy only in part and mostly covered with gravels; the vegetation is very sparse. Three further collecting attempts in 2015 were not successful: in May and September the brook was flowing too strongly and in July the senior author found only some specimens of Nebrioporus stearinus stearinus (KOLENATI, 1845) and Scarodytes halensis .

E t y m o l o g y: The specific name costatus is an adjective in the nominative singular. It is a Latin word meaning "provided with ribs" and relates to the costate elytra of the new species (see NILSSON 2010: 10 and STEARN 2005: 393).

Figures

Fig. 1: Oblique frontal view of Scarodytes costatus nov.sp.

Figs 2-5: Habitus of: Scarodytes costatus nov.sp. (2) holotype (male) and (3) paratype (female); (4) S. halensis (female from Wallern, Lake Neusiedel, Austria); (5) Nebrioporus carinatus (male from Esclavitud, La Coruña, Spain) (scale bar 4 mm for Scarodytes, 5.2 mm for Nebrioporus).

Figs 6-9: Punctation on metaventrite and metacoxal plate of: (6) Scarodytes costatus nov.sp. (holotype; left mid-leg removed); (7) S. fuscitarsis (male from Arbatax, Sardinia, Italy); (8) S. halensis (female from Oldenburg, Celle, Germany; left mid-leg removed); (9) Nebrioporus carinatus (male from Camporredondo, Lugo, Spain).

Figs 13-14: Details of mesoventral column in frontal view of (13) Scarodytes fuscitarsis (female from Arbatax, Sardinia, Italy); (14) Nebrioporus carinatus (male from Tabladillo, León, Spain); arrows point on lateral surfaces of mesoventral column, being parallel in Scarodytes and, thus, invisible in frontal view, but well visible in Nebrioporus because diverging backwards (lateral surfaces in Fig. 14 somewhat lightened); meaning of letters as in Fig. 12.

Figs 15-16: Details of mesoventral column in ventral view of (15) Scarodytes halensis (male from Oldenburg, Celle, Germany); (16) Deronectes hispanicus (male from N Jimena de la Frontera, Cádiz, Spain; left mid-leg disarticulated); meaning of letters as in Fig. 12.

Figs 10-12: (10) "SHARP's T" – modified from figure 23 of plate VII in SHARP 1882; drawn by SHARP after a Dytiscus marginalis L. (meaning of letters a-d same as in Fig. 12); (11) Scarodytes costatus nov.sp. (paratype): mesocoxal processes; arrow pointing on weakly exposed interlaminary bridge; (12) Nebrioporus carinatus: frontal view on mesoventrite and mesoventral column (male from Tabladillo, León, Spain). Arrows point on: (a) mesepisternum, (b) mesepimeron, (c) SHARP's "portion of margin of middle coxal cavity", (d) frontal surfaces of mesoventral column ("facettes" of SHARP's "medisternum"), (e) tines if mesoventral ("mesosternal") fork, (f) lateral surfaces of mesoventral column, (g) anteromedial metaventral process, (h) metepisternum, (i) elytral epipleuron, (j) mesocoxae.

Figs 18-20: Scarodytes costatus nov.sp.: median lobe of aedeagus in ventral (18) and lateral (19) view; left paramere (20) (scale 0.5 mm).

Figs 21-22: Type locality of Scarodytes costatus nov.sp. – two rest pools of Hazarşah brook in August 2014.