Ryukyuaphaenops pulcherrimus, Sugaya & Kakizoe & Ooka & Tamura & Sone, 2023

Sugaya, Kazuki, Kakizoe, Showtaro, Ooka, Sohei, Tamura, Hisao & Sone, Shinzaburo, 2023, Discovery of a troglomorphic trechine beetle from the Ryukyu Archipelago, Southwestern Japan (Coleoptera: Carabidae: Trechinae), Acta Entomologica Musei Nationalis Pragae 63 (2), pp. 323-340 : 329-336

Ryukyuaphaenops pulcherrimus sp. nov.

Japanese name: †キ±77̐±fl̽yṽŧõiì^̐

( Figs 3–24 , 28 )

Type material. HOLOTYPE: J, KSES00004 ( NSMT), “ JAPAN: Okinawa-ken , Okinawa-jima Is., / Motobu-chō , Furujima, Ufugushikumui- / abu-dai-ichi Cave [ŀĸ⁂7ĪDZ / ͠], 26.6744°N, 127.9056°E, (el. 220m), / 28 II 2022, H. TAMURA” (printed on white label), “ HOLOTYPE / Ryukyuaphaenops / pulcherrimus / des. Sugaya, Kakizoe, Ooka, / Tamura & Sone, 2023” (printed on red label) . PARATYPES (35 JJ 40 ♀♀): 1 ♀, KSES00001 ( NSMT), same locality as the holotype, 10.xii.2021, S. Ooka leg.; 2 JJ, KSES00002, 00003 ( NSMT), same locality and date as above, H. Tamura leg. [KSES00003: DNA voucher (SK185)]; 1 J 1 ♀, KSES00024, 00025 ( KSTJ), same locality as above, 7.vi.2022, S. Ooka leg.; 4 JJ, KSES00033–00036 ( NSMT), same locality as above, 8.vi.2022, H. Tamura leg. [KSES00033: subdivided into micro parts for the detailed examination; KSES00036:DNA voucher (SK193), teneral]; 1 J 1♀, KSES00005, 00018 ( NSMT), Cave A, Ufudō (̂fi), Motobu-chō, Okinawa-ken, 10.iii.2022, H. Tamura leg. [KSES00018: subdivided into micro parts for the detailed examination; found teneral but reared and died in 12.vii.2022]; 1 ♀, KSES00006 ( KSTJ), same locality and date as above; 1♀, KSES00007 ( NSMT), same locality and date as above, S. Ooka leg.; 1J 1 ♀, KSES00008, 00009 ( KSTJ), same locality as above, 3.iv.2022, K. Uchida leg.; 1♀, KSES00017 ( SKIJ),same locality and date as above, S. Kakizoe leg.; 1 ♀, KSES00028 ( NSMT), same locality and date as above, D. Sumikawa leg. [DNA voucher (SK197); teneral]; 1 ♀, KSES00026 ( NSMT), same locality and date as above, K. Sugaya leg. [DNA voucher (SK199); found teneral but reared and died in 5.vi.2022]; 1 J, KSES00010 ( KSTJ), same locality as above, 2.iv.2022, K. Sugaya leg.; 1 J 2 ♀♀, KSES00012–00014 ( NSMT), same locality and date as above, K. Nishigaki leg.; 1 J 1 ♀, KSES00016, 00027 ( NSMT), same locality and date as above, S. Kakizoe leg. [KSES00027: DNA voucher (SK195)]; 1 J, KSES00015 ( SKIJ), same locality and date as above, S. Kakizoe leg.; 1 J, KSES00019 ( NSMT), same locality and date as above, S. Sone leg. [found teneral but reared and died in 21.vii.2022]; 1 J, KSES00032 ( NSMT), same locality as above, 20.iv.2022, H. Tamura leg.; 2♀♀, KSES00021, 00022 ( NSMT), same locality and date as above, Ooka & H. Tamura leg. [in a baited trap set by S. Kakizoe on 3.iv.2022]; 1 ♀, KSES00023 ( NSMT), same locality as above, 25.v.2022, S. Ooka leg.; 2♀♀, KSES00030, 00031 ( NSMT), same locality and date as above, H. Tamura leg. [in a baited trap set by S. Kakizoe on 3.iv.2022]; 1 ♀, KSES00121 ( NSMT), same locality as above, 1.x.2022, S. Kakizoe leg. [preserved in 99.5% ethanol]; 1 ♀ KSES00037 ( NSMT), same locality and date as above, S. Kakizoe leg. [subdivided into micro parts for the detailed examination; in a baited trap set by S. Kakizoe on 3.iv.2022]; 1 J 1 ♀, KSES00038, 00039 ( EUMJ), same data as above [complete condition]; 1 J 1 ♀, KSES00056, 00066 ( SHSJ), same data as above; 1 J 1 ♀, KSES00040, 00041 ( HUM), same data as above; 5 JJ 5 ♀♀,

KSES00042–00051 ( KSTJ), same data as above; 1 J 1 ♀, KSES00052, 00053 ( KUM), same data as above; 1J 1♀, KSES00057,00067 ( NMPC), same data as above; 1 J 1 ♀, KSES00054, 00055 ( RUMJ: RUMF- -ZI-53351, 53352), same data as above; 8JJ 8♀♀, KSES00058–00065, 00068–00075 ( SKIJ), same data as above; 1 J, KSES00120 ( NSMT), same locality and date as above, S. Ooka leg. [used for Videos S1, S2; preserved in 99.5% ethanol]; 1 ♀, KSES00114 ( SKTJ), same locality and date as above, S. Kawai leg.; 1 ♀, KSES00115 ( NSMT), Cave B, Ufudō, Motobu-chō, Okinawa-ken, 8.iv.2023, K. Sugaya leg. [DNA voucher (SK202)].

Additional material examined (incomplete specimens mainly from traps). 12 JJ 29 ♀♀ 4 spec.: 1 ♀, KSES00011 ( DSSJ), Cave A, Ufudō (̂fi), Motobu-chō, Okinawa-ken, 3.iv.2022, D. Sumikawa leg.; 1 ♀, KSES00029 ( KSTJ), same locality as above, 25.v.2022, H. Tamura leg. [teneral; in a baited trap set by S. Kakizoe on 3.iv.2022]; 6 ♀♀, KSES00076–00081 ( KSTJ), same locality as above, 1.x.2022, S. Kakizoe leg.[in a baited trap set by S. Kakizoe on 3.iv.2022]; 1J 1♀, KSES00082, 00083 ( KUGJ), same data as above; 5 JJ 5 ♀♀, KSES00084–00093 ( SKIJ), same data as above; 5 JJ 15 ♀♀ KSES00094–00113 ( KSTJ), same data as above [incomplete condition]; 1 spec., KSES00020 ( KSTJ), Cave B, Ufudō, Motobu-chō, Okinawa-ken, 3.iv.2022, K. Sugaya leg. [found dead, only elytra]; 1 J 3 spec., KSES00116–00119 ( KSTJ), same locality as above, 8.iv.2023, K. Sugaya leg. [found dead with some body parts].

Diagnosis. This species is readily distinguished from all other Trechina by the generic diagnostic characteristics mentioned above.

Description. Males and females. Color ( Figs 3 , 4 ) light to dark reddish brown; palpi, apical half of antennae, tibiae and tarsi a little lighter. Body surface polished and not iridescent, sparsely covered with very minute microscopical hairs except for clypeus, neck, gula, scutellum, mesoventrite, metaventrite, and lateral parts of each sternite.

Head ( Figs 3 , 4 , 18 ) much longer than wide, widest at about level of anterior supraorbital pore; neck as wide as 3/4 of HW; dorsum transversely rugose on frons and supraorbital areas, and usually with pair of supplemental hairs on posterior inner sides of anterior and posterior supraorbital pores, respectively; vertex without suprafrontal seta; frontal furrows distinct though absent behind level of anterior supraorbital pore; supraorbital pores located in about apical 1/2 and 1/5 of HL, respectively;microsculpture distinct, deeply impressed anteriorly, almost consisting of isodiametric polygonal meshes, but transverse meshes laterally; genae hardly convex laterad, and sparsely covered with a few hairs both on latero-ventral and ventral surface, former is usually longer than latter: ventral surface of genae ( Figs 18b, 18c ) transversely rugose. Labrum ( Figs 6 , 16 ) with apical margin shallowly trisinuate. Right mandible ( Figs 4 , 5b ) usually bidentate; proximal tooth of retinaculum usually missing. Labial suture ( Figs 7 , 17 ) unrecognizable though with very shallow trace in just middle portion; mental tooth bifid; submentum usually octosetose. Antennae ( Fig. 3 ) less than twice as long as EL, slightly longer in male than female; segment 1 shortest and segment 5 longest, of all segments; segments 2–5 each gradually longer than preceding segment; segments 6–10 each gradually shorter than preceding segment; segment 11 as long as segment 9; approximate ratios of left antennal segments 1–11 as follows: holotype: 1.0: 1.4: 2.3: 2.6: 2.7: 2.6: 2.4: 2.1: 1.9: 1.7: 1.9; male (n = 15, including holotype): 1.0: 1.3: 2.1: 2.6: 2.8: 2.5: 2.2: 2.0: 1.9: 1.7: 2.0; female (n = 15): 1.0: 1.3: 2.1: 2.4: 2.6: 2.4: 2.2: 2.0: 1.9: 1.7: 1.8.

Pronotum ( Figs 3 , 4 , 19 ) slightly wider than head, as long as head, much longer than wide, widest before middle, and more gradually narrowed toward base than apex; dorsum almost smooth but with fine confused transverse rugosity along pronotal sides; microscopic hairs sparser and finer than those of head, almost absent around basal foveae; lateral margins moderately arcuate, though shallowly concave around anterior marginal pore and feebly emarginated before hind angles; microsculpture distinct, almost consisting of transverse meshes, gradually deepened and narrowed laterad; side borders ( Figs 19a, 19b ) incomplete, very fine and hardly reflexed, vestigial near middle and completely absent near apices; lateral declivities of pronotum ( Figs 19a, 19b ) feebly visible from above in about middle; anterior latero-marginal pores present, located in apical 1/4 of PL, and adjoining marginal gutter; posterior latero-marginal pores absent; each basal fovea with bottom almost smooth but usually forming a few oblique ridges parallel to oblique side of basal margin and terraced; postangular carinae absent; basal area uneven and longitudinally strigose. Propleura ( Figs 4 , 19a, 19b ) very narrowly visible from above behind middle. Scutellum elongated triangle.

Prosternum ( Fig. 19c ) sparsely covered with short hairs on anterior area near middle; metaventrite with pair of long hairs along midline near middle, and sparsely covered with short hairs except for lateral sides and posterior area.

Elytra ( Figs 3 , 4 , 20, 21 ) slightly wider and obviously longer than pronotum, much longer than wide, widest behind middle; dorsum well convex, distinctly higher than pronotum; basal depression extending on more than basal 1/5 of EL; microscopic hairs extremely sparse and fine, hardly recognizable under optical microscope except for marginal area; microsculpture distinct but very fine, almost consisting of long transverse meshes; prehumeral margins strongly oblique and moderately emarginated; prehumeral borders entirely ( Fig. 20 ) visible from above even in basal portion, though gradually vestigial anteriad and completely absent at basal peduncle; shoulders distinct, slightly produced antero-laterad and reflexed intero-dorsad though widely rounded, placed in about basal 1/5 of EL, about twice as wide as elytral base, about 3/4 as wide as EW; lateral margins feebly emarginated behind shoulders, then moderately arcuate and convergent to apices; preapical emarginations very obtuse; marginal cilia and serrations ( Fig. 20a ) present from base of prehumeral margins to preapical emarginations, both very sparse and very fine though slightly more dense and prominent around shoulders; striae very shallow and indistinct, gradually evanescent laterad, and very sparsely and very faintly punctate; stria 1 almost disappearing, though deeply impressed at basal part; striae 2 and 3 distinct and slightly deeper than outer striae, though vestigial near both ends; striae 4 and 5 very fine and very superficial, and vestigial near both ends; striae 6 and 7 barely traceable; stria 8 almost disappearing, though deeply impressed around 4th pore and 5th to 6th pores of marginal umbilicate pores; intervals feebly convex except for basal depression and posthumeral lateral area; interval 8 swelled around middle set of marginal umbilicate pores; scutellar striole indistinct; apical striole ( Fig. 21 ) vestigial and usually not connected with any striae; apical carina ( Fig. 21 ) barely recognizable; basal pore located at about level of a little anterior portion of apex of scutellum; two setiferous dorsal pores on stria 3 each located in about basal 3/10 and 3/5 of EL, anterior pore lying before level of 4th pore of marginal umbilicate series, and posterior one at same or just behind level of 5th pore of marginal umbilicate pores; preapical pore located in about apical 1/7 to 1/9 of EL, lying at about before level of 8th pore of marginal umbilicate series, closer to elytral suture than to elytral apices; anterior apical pore slightly closer to elytral suture than to preapical pore, much closer to elytral apices than to elytral suture; posterior apical pore equally very close to both elytral suture and elytral apices.

Sternites 3–7 ( Figs 22, 23 ) each densely covered with short to long hairs near middle along posterior margin; sternites 4–6 each bearing with pair of paramedian setae.

Metafemur and metatibia about 4/5 and 3/4 as long as elytra, respectively; metatarsus about 3/4 as long as metatibia; tarsomere 1 not longer than tarsomeres 2–4 together in fore legs, but evidently longer in middle and hind legs.

Male genital organ as in Figs 11–13 (n = 13). Median lobe ( Fig. 11 ) less than 1/5 as long as EL, moderately arcuated and almost symmetrical; ventral margin hardly concave in just distal portion of junction with styles; basal part less than 1/5 as long as median lobe; basal orifice broadly opening on basal end of basal part; sagittal aileron hyaline, baso-ventrally protruded; apical lobe about 1/2 as long as median lobe, almost straight and gradually tapering toward rounded apex; in dorsal view, apical lobe symmetrical elongated triangle, widely rounded at apex. Internal sac ( Figs 11, 12 ) simply invaginated in median lobe; internal sac in fully inflated condition with eversion (n = 3) projected dorso-apically from apical orifice, about 2/9 as long as median lobe, oblong bulbous, sparsely covered with fine hyaline scales, and devoid of sclerotized teeth patches; copulatory piece attached on apical end of internal sac, asymmetrical spatulate, about 1/2 as long as internal sac and 1/5 as long as median lobe, moderately sclerotized, sparsely covered with very fine spicules, with apical margin irregularly serrate; basal part of copulatory piece covered by internal sac and never exposed. Styles ( Figs 11a, 11b ) without ventral apophysis.

Female genital organ as in Figs 14, 15 (n = 14). Bursa copulatrix elongated tube-shaped, clearly distinguishable from bulbous vagina, distinctly longer than vagina, and widely rounded at extremity; spermathecal complex elongated bulbous, extending toward vagina; common oviduct branching from middle part of vagina ventrally.

Larva and pupa. Unknown.

Measurements and ratios. See Table 1 and 2.

Variation. Character states are stable between the three populations. On the other hand, some individual variations not related to the geographic origin of the specimen were recognized: presence of supplemental hairs on supraorbital area of head; degree of development of right mandibular proximal tooth of retinaculum (usually missing: Fig. 4 , but sometimes perceptible and very slightly prominent: Fig. 5b ); number of submental setae (six to nine setae); strength and state of engraving of pronotal basal foveae; degree of development of pronotal hind angles, serration on elytral shoulders, elytral striae, and apical striole of elytra (usually vestigial, but if perceptible, barely directed to termination of stria 5); position of elytral setiferous dorsal pores (frequently unstable between each elytron even in a single specimen; in holotype, position of anterior pore of left elytron exceptionally behind level of 4th pore of marginal umbilicate series: Fig. 4 ); presence of elytral scutellar striole, and posterior apical pore of elytra; presence of supplemental fairly long hairs on sternites 4–6 (sometimes present at inner part of paramedian setae on both or one side of some sternites, more frequently on sternites 4 and 5); number of paramedian setae on sternite 7 in female (usually two pairs but sometimes three pairs); 14) degree of curvature of median lobe, and size of sagittal aileron.

Etymology. The specific name is derived from the superlative of the Latin adjective pulcher, meaning the most beautiful; adjective.

Habitat information. Ufugushikumui-abu-dai-ichi Cave, the type locality of the present new species is located in the northwestern part of the Motobu Peninsula ( Figs 2 , 25–27 ), and included in the special protection zone of the Okinawa Kaigan Quasi-National Park. This cave opens near the peak of Mt. Ufugushikumui (237 m above sea level) and is composed of two pitches. The first and second pitch are about 35 m and 13 m deep, respectively, and are connected by a constriction. The floors of both caves are covered with rubble. The individuals of Ryukyuaphaenops pulcherrimus gen. nov. & sp. nov. were found only in the second pitch, with most individuals walking on moist stalagmitic walls. The air temperature and the relative humidity of the bottom were about 21°C and 100%, respectively (measured on 1 st November 2022). Although biological surveys were conducted in this cave in the past, no trechine beetles were found before ( SHIMOJANA 1979).

Cave A, the second known locality, is about 1.3 km to the east from the type locality. This cave opens on a small conical hill and is about 15 m deep. The floor is connected to a small room (about 4 × 7 m wide) via a narrow horizontal passage. The floor of the room is extensively covered with thickly deposited clay and rubble. The individuals of Ryukyuaphaenops pulcherrimus gen. nov. & sp. nov. were collected in the room and most individuals were walking on moist stalagmitic walls (see Videos S1–S2). The air temperature and the relative humidity of the room were about 22.1°C and 100%, respectively (measured on 8 th June 2022).

Cave B, the third known locality, is about 150 m to the east from Cave A. This cave has a large entrance and is dry on a wide area and composed of two pitches. The depth of the first and second pitch are about 5 m and 7 m, respectively. The individual of Ryukyuaphaenops pulcherrimus gen.nov. & sp. nov. was found in the narrowest part of the second pitch, which is highly humid. Despite multiple intensive surveys, only single female specimen and some body parts have been found in this cave. The air temperature and the relative humidity of the second pitch were about 17.4 °C and 93%, respectively (measured on 8 th April 2023).

Distribution. Japan: Okinawa-jima Island in the Ryukyus ( Figs 1 , 2 ) (known only from three pit caves in the Motobu Peninsula).

Figures

Fig. 3. Habitus of Ryukyuaphaenops pulcherrimus gen. & sp. nov., holotype male (KSES00004), dorsal (a) and lateral (b) views.

Fig. 4. Chaetotaxy of Ryukyuaphaenops pulcherrimus gen. & sp. nov., holotype (KSES00004), dorsal (a) and dorso-lateral (b) views.

Figs 5–10. Body parts of Ryukyuaphaenops pulcherrimus gen. & sp. nov., paratypes (5 – KSES00018; 6–10 – KSES00033). 5 – left (a) and right (b) mandibles, dorsal view; 6 – labrum, dorsal view; 7 – labium, ventral view; 8 – ligula and labial palpus, ventral view; 9 – left maxilla, ventral view; 10 – left protarsi of male, dorsal (a) and internal (b) views.

Figs 11–15. Male (11–13) and female (14, 15) genital organs of Ryukyuaphaenops pulcherrimus gen. & sp. nov. 11, 13 – holotype (KSES00004); 12, 14, 15 – paratypes (12 – KSES00005; 14 – KSES00001; 15 – KSES00037). 11 – median lobe, left lateral (a), right lateral (b) and dorsal (c) views; 10 – internal sac, left lateral (a), right lateral (b), front (c) and behind (d) views; 13 – genital segment, reversed side view; 14 – left gonocoxite, ventral view; 15 – reproductive tract, left lateral view.Abbreviations: bc – bursa copulatrix; co – common oviduct; sp – spermathecal complex; vg – vagina.

Figs 16–19. SEM photos of body parts of Ryukyuaphaenops pulcherrimus gen. & sp. nov., holotype (KSES00004). 16 – labrum; 17 – labium; 18 – head; 19 – prothorax. a – dorsal view; b – dorsolateral view; c – ventral view. Abbreviations: ha – hind angle; ld – lateral declivity; nps – notopleural suture; pp – propleura; sb – side border.

Figs 20–24. SEM photos of body parts of Ryukyuaphaenops pulcherrimus gen. & sp. nov., holotype (KSES00004). 20 – basal part of right elytron, left latero-dorsal (a) and right latero-dorsal (b) views; 21 – apical part of right elytron, right latero-dorsal view; 22 – sternites 3 and 4; 23 – sternites 5–7; 24 – microscopic hairs and microsculpture in head (a), pronotum (b) and elytra (c).Abbreviations: ac – apical carina; as – apical striole; pb – prehumeral border.

Figs 25–28. Habitat of type locality (25–27) and living individual (28) of Ryukyuaphaenops pulcherrimus gen. & sp. nov. 25 – Mt. Ufugushikumui; 26 – entrance of Ufugushikumui-abu-dai-ichi Cave; 27 – inside of Ufugushikumui-abu-dai-ichi Cave; 28 – living individual at the wall face of Ufugushikumui-abu-dai-ichi Cave.

Fig. 2. Map showing present study area, Motobu Peninsula (black arrow), and locality of Ryukyuaphaenops pulcherrimus gen. & sp. nov. (black star).

Fig. 1. Location of the Ryukyu archipelago and distribution of troglomorphic Trechina in East Asia.