Edaphus nagugushikuensis Jałoszyński & Sapieja, 2022

Jałoszyński, Paweł & Sapieja, Mateusz, 2022, A new Ryukyuan species of Edaphus Motschulsky (Coleoptera, Staphylinidae Euaesthetinae), Zootaxa 5178 (6), pp. 583-588 : 584-587

Edaphus nagugushikuensis Jałoszyński & Sapieja sp. n.

( Figs 1–5 )

Type material. Holotype: Japan, Okinawa-jima : ♂, two labels: “ JAPAN, Okinawa Pref. / OKINAWA-jima, N / Nago Castle Site / forest, sifted, 24 II 2020 / leg. P. Jałoszyński ” [white, printed], “ EDAPHUS / nagugushikuensis / Jałoszyński & Sapieja, 2022 / HOLOTYPUS” [red, printed] ( NSMT).

Diagnosis. Each dorsal tentorial pit situated at mesal margin of large, suboval and shallow impression; furrows extending anterad from each dorsal tentorial pit parallel and slightly shorter than length of compound eye in dorsal view; median longitudinal pronotal carina distinctly longer than half length of pronotum, gradually narrowing posterad, its lateral edges just in front of posterior pronotal margin rapidly curved laterad and continuous with fine marginal carina; lateral carinae of pronotum distinctly converging anterad, as long as half-length of pronotum; pronotal base with transverse row of three pairs of large but shallow and diffuse pits, largest pit adjacent to median carina and separated from sublateral pit by distinct carinula; length of elytral suture indistinctly shorter than elytral width; anteromedian longitudinal carina of abdominal tergite III slightly shorter than half length of tergite; sperm pump lacking funnels and distinctly curved; median lobe of aedeagus in dorsal view with distinct constriction in submedian region that delimits proximal oval region and distal subtriangular portion, the latter slightly shorter than proximal region; lateral margins of distal region weakly rounded but just at apex sinuate to form narrow subtriangular apical projection; endophallus in dorsal view symmetrical, with particularly large X-shaped proximal structure distally connected to minute median M-shaped sclerite; parameral apices slightly exceeding half-length of distal portion of median lobe, each bearing long subapical and slightly shorter apical seta.

Description. Body of male ( Fig. 1 ) moderately dark brown and glossy; appendages slightly lighter, except for weakly infuscate antennomeres 10 and 11. Setae slightly lighter than cuticle. BL 0.99 mm.

Head ( Fig. 1 ) subtrapezoidal, distinctly narrower than pronotum, broadest at eyes, HL 0.14 mm, HW 0.21 mm. Eyes large, slightly oval, longitudinally elongate, strongly convex and coarsely faceted, situated posteriorly. Tempora in dorsal view strongly curved posteromesad, each about 0.2 times as long as eye. Vertex subtrapezoidal, broadest posteriorly, weakly convex, anteriorly demarcated by diffuse transverse groove connecting dorsal tentorial pits, laterally by sharply marked lateral grooves that are strongly converging anteromesad. Frons in front of eyes strongly transverse, rapidly narrowed just behind supraantennal tubercles where it bears pair of nearly transverse postantennal grooves, each about as long as 1/3 of width of anterior frontal margin, which is broadly rounded. Sides of frons between eyes with pair of large and shallow suboval impressions mesally adjacent to dorsal tentorial pits and posteromesally to lateral grooves demarcating vertex and tempora; anteriorly each impression prolonged into narrow lateral longitudinal groove parallel to long body axis. Dorsum of head virtually impunctate, with sparse and weakly suberect setae distributed along dorsomesal margins of eyes, posterior to lateral frontal impressions, and on anterior region of frons. Antennae 11-segmented, club indistinctly trimerous, i.e., antennomeres 10 and 11 strongly enlarged, whereas width of antennomere 9 intermediary between that of 8 and 10, AnL 0.28 mm. Antennomeres 1‒5 each elongate (1 and 2 strongly, 3‒5 slightly so), 6 about as long as broad, 7‒9 each transverse, 9 strongly narrowing distad in distal half, 10 barely noticeably elongate, 11 indistinctly broader than 10, 1.2 × as long as broad.

Pronotum ( Fig. 1 ) cordiform, broadest slightly in front of middle, slightly transverse; PL 0.23 mm, PW 0.25 mm. Anterior pronotal margin nearly straight and with narrow marginal bead, anterior corners broadly rounded, sides strongly rounded in anterior half, distinctly concave in posterior third; posterior corners clearly marked, obtuse-angled and blunt; posterior margin weakly arcuate, with narrow median marginal carina. Pronotal disc with median longitudinal carina anteriorly exceeding middle of pronotum, posteriorly strongly narrowing, its lateral edges just in front of posterior pronotal margin rapidly curved laterad and continuous with posterior marginal carina. Lateral longitudinal carinae sharply marked on entire length and anteriorly reaching middle of pronotum, slightly converging anterad. Pronotal base with transverse row of three pairs of large and shallow pits; median pair largest and slightly elongate, mesally adjacent to median longitudinal carina, sublateral and lateral pit round, median and sublateral pits separated by short carinula broadening in front and behind pits. Punctures on pronotal disc virtually absent; setae sparse and only slightly suberect, mostly directed toward midline.

Elytra ( Fig. 1 ) broadest just behind middle; EL 0.28 mm, EW 0.33 mm, EI 0.85. Elytral base distinctly concave, humeri obtuse-angled, sides distinctly convex and evenly rounded, posterior margins strongly concave, sutural striae sharply marked. Punctures on elytra as indistinct as those on pronotum; setae sparse and only slightly suberect, largely directed posterad or posterolaterad, but those on posterior 1/5 of each elytron directed strongly laterad and only slightly posterad.

Mesoscutellar shield minute and poorly visible, only its rounded, subtriangular tip exposed.

Hind wings not shortened, functional.

Abdomen ( Fig. 1 ) indistinctly broader than pronotum and distinctly narrower than elytra; AbL 0.35 mm, AbW 0.28 mm. Tergite III with median longitudinal carina not reaching its middle. Sternite VIII ( Fig. 2 ) with deeply emarginate posterior margin, emargination strongly rounded and slightly broader than 1/3 width of sternite. Surface of tergites and paratergites lacking microsculpture, with punctures and setae similar to those on elytra; all setae directed posterad or posteromesad.

Sperm pump ( Fig. 3 ) strongly sclerotized, lacking funnels, strongly curved, 0.075 mm long.

Aedeagus ( Figs 4–5 ) elongate; AeL 0.18 mm; median lobe in dorsal view with distinct constriction in submedian region that delimits proximal oval region and distal subtriangular portion, the latter slightly shorter than proximal region; lateral margins of distal region weakly rounded but just at apex sinuate to form narrow subtriangular apical projection; endophallus in dorsal view symmetrical, with particularly large X-shaped proximal structure distally connected to minute median M-shaped sclerite; parameral apices slightly exceeding half-length of distal portion of median lobe, each bearing long subapical and slightly shorter apical seta.

Female. Unknown.

Distribution. Central Ryukyus, Okinawa-jima.

Etymology. The adjective nagugushikuensis is derived from Nagu Gushiku, the name of the Nago Castle (Japanese: Nago-jō) in uchinaaguchi, i.e., the Okinawan language. The holotype was collected on a hill where, six centuries ago, stood the Nago Castle.

Remarks. Among currently known six species of Edaphus that inhabit Okinawa-jima, E. nagugushikuensis sp. n. differs (besides unique structures of the aedeagus):

- from E. okinawaensis in having distinct anterolateral grooves extending anterad from dorsal tentorial pits; and distinct median longitudinal pronotal carina (both lacking in E. okinawaensis );

- from E. riukiuensis in anterolateral grooves extending anterad from dorsal tentorial pits running parallel (in E. riukiuensis distinctly converging anterad); antennomere 10 indistinctly elongate (in E. riukiuensis distinctly transverse); the pronotal base with three pairs of pits (in E. riukiuensis with four pairs); and in impunctate pronotal disc (in E. riukiuensis distinctly punctate);

- from E. perexilis in distinctly transverse pronotum with strongly rounded anterior corners, median longitudinal carina narrowing only posteriorly, lateral carinae reaching middle of pronotum and pronotal disc impunctate (in E. perexilis the pronotum is weakly elongate, with blunt but clearly marked anterior corners, median longitudinal carina narrowing both anteriorly and posteriorly, lateral carinae reaching only posterior third of pronotal length, and the median region of pronotal disc covered with distinct punctures);

- from E. diversipunctatus in antennomere 10 indistinctly elongate (in E. diversipunctatus distinctly transverse); sides of pronotum in anterior half strongly rounded (in E. diversipunctatus nearly straight); median longitudinal carina of pronotum anteriorly not reaching to anterior pronotal margin (in E. diversipunctatus nearly as long as entire pronotum); and pronotal disc impunctate (in E. diversipunctatus coarsely, densely and irregularly punctate);

- from E. silvius in head and pronotum impunctate (in E. silvius densely, deeply and coarsely punctate); transverse groove connecting dorsal tentorial pits straight (in E. silvius V-shaped, posteriorly convex); and pronotum strongly transverse, with broadly rounded anterior corners, and bearing median longitudinal carina, lateral carinae and a transverse row of six large and distinct antebasal pits (in E. silvius pronotum about as long as broad, its anterior corners are clearly marked and only slightly obtuse-angled, and pronotal base lacks any longitudinal carinae or large antebasal pits).

Among Edaphus species that are known to occur in Palaearctic and Oriental regions, some have simple endophalli restricted to the distal (subapical) region of the median lobe, and others have complex and large endophallic structures that occupy a large portion of the proximal region of the median lobe and extend distally into the subapical area. Edaphus nagugushikuensis sp. n. belongs to the latter group, and its proximal X-shaped endophallic structure is especially large and darkly sclerotized. Slightly similar (but not identical) proximal endophallic structures can be found in the Japanese E. nipponensis Puthz, 1975 , E. iriomoteanus Puthz, 2010a , E. bannadakemontis Puthz, 2010a , E. nomurai Puthz, 2010a , E. ogatai Puthz, 2010a ; Taiwanese E. klapperichianus Puthz, 2010b , E. mimus Puthz, 2010b , E. perodibilis Puthz, 2010b , E. mimulus Puthz, 2010b , E. odibilis Puthz, 2010b , E. semipunctatus Puthz, 2010b , E. callifrons Puthz, 2010b , and E. viti Puthz, 2010b . Among them, E. nagugushikuensis sp. n. has the proximal endophallic region particularly long and broad, with clearly differentiated and strongly proximally divergent basal ‘arms’, and an M-shaped minute endophallic component nearly at the level of the constriction of the median lobe. Other species with slightly similar, large endophalli have either different shapes of the median lobe (including different proportions of the proximal and distal regions), or different arrangement and shapes of endophallic sclerites.

Figures

FIGURES 1–5. Edaphus nagugushikuensis sp. n., holotype male. Dorsal habitus, excluding posterior portion of abdomen (1); abdominal sternite VIII (2); sperm pump (photographed through abdominal tergite) (3); aedeagus in dorsal view (4, 5).