Gyrinus smaragdinus Régimbart, 1891

Suksai, Benjamart, Gustafson, Grey T., Sites, Robert W. & Sangpradub, Narumon, 2021, The Gyrinidae (Coleoptera) fauna of Thailand: Key to tribes and genera, with new records and keys to species of Dineutini and Gyrinini, Zootaxa 5071 (1), pp. 97-117 : 99-102

Gyrinus smaragdinus Régimbart, 1891

( Figs. 1B , 2 , 3C–E , 7A–B , 8A )

Material examined. THAILAND: Chiang Mai Province: Doi Inthanon Natl. Park, Mae Klang at Ban Khun Klang , 18°31.259'N 98°31.310'E, 1296 m a.s.l., 18.V.2004, leg. T. Prommi, A. Vitheepradit, P. Laudee & P. Thamasenanupap, L-694, 3 males, 9 females ( UMC) ; same locality except for, Pha Dum Waterfall , 18°36'N 98°31'E, 1379 m a.s.l., 3.V.2003, leg. UMC & CMU teams, L-499, 3 males, 2 females ( UMC) ; same locality except for, Siriphum Waterfall (lowest level), 18°32'N 98°31'E, 1460 m a.s.l., 21.III.2002, leg. R.W. Sites, A. Vitheepradit & K. Kirawanich, L-315, 4 males, 3 females ( UMC) ; same locality except for, 9.V.2002, leg. UMC & CMU teams, L-401, 3 males ( UMC) ; same locality except for, stream from Huai Sai Luang Waterfall , 18°31'N 98°27'E, 1060 m a.s.l., 8.V.2002, leg. UMC & CMU teams, L-396, 27 males, 27 females ( UMC) ; Doi Suthep Natl. Park, Monthathan Waterfall , 18°49'N 98°55'E, 700 m a.s.l., 11.I.2003, leg. CMU Team, 1 male ( UMC) ; same locality except for, 14.II.2003, leg. CMU Team, 1 male ( UMC) ; Pond at Ban Buak Thoei, Pong Yaeng Subdistrict , Mae Rim District , 18°53'30.2"N 98°47'36.5"E, 1153 m a.s.l., 29.IV.2018, leg. B. Suksai, S. Kullasoot, C. Yatfung & P. Sapewisut, 2 males, 1 female ( THNHM) . Kanchanaburi Province: Thong Pha Phum Natl. Park, Huay Ka Yeang Stream, Hin Dat Subdistrict , Thong Pha Phum District , 14°33'18.0''N 98°35'51.8''E, 270 m a.s.l., 25.II.2002, leg. S. Saeheag, 2 males ( KKU, THNHM) , 1 female ( THNHM) . Loei Province: Phu Hin Rongkla Natl. Park, Man Daeng Noi at trail, 16°57'N 101°03'E, 1600 m a.s.l., 5.V.2003, leg. N. Changthong, 20 males, 18 females ( UMC) ; same locality except for, 1340 m a.s.l., 6.V.2003, leg. A. Vitheepradit, T. Prommi & M.L. Ferro, L-504, 10 males, 16 females ( UMC) ; Phu Kradueng Natl. Park, stream from Tham Yai Waterfall, Si Than Subdistrict , Phu Kradueng District , 16°52'59.9"N 101°46'46.4"E, 1197 m a.s.l., 7.XII.2010, leg. N. Sangpradub, 1 female ( KKU) ; same locality except for, Tham Sor Nuo Waterfall, Si Than Subdistrict, Phu Kradueng District , 16°52'36.2"N 101°44'48.2"E, 1234 m a.s.l., 8.III.2011, leg. N. Sangpradub, 1 male, 1 female ( THNHM) ; same locality except for, Wang Kwang Waterfall, Si Than Subdistrict, Phu Kradueng District , 16°53'29.5"N 101°47'03.5"E, 1221 m a.s.l., 6.III.2011, leg. N. Sangpradub, 2 females ( KKU) . Nan Province: Doi Phuka Natl. Park, Ton Thong Waterfall , 19°12'N 101°04'E, 900 m a.s.l., 21.IV.2003, leg. A. Vitheepradit, T. Prommi & K. Setaphan, L-472, 4 males, 1 female ( UMC) ; stream at Khun Sathan Natl. Park, Ban Mueng Li, Mueng Li Subdistrict , Na Muen District , 18°15'08.4"N 100°29'35.8"E, 786 m a.s.l., 29.V.2017, leg. P. Sapewisut, 1 male, 1 female ( THNHM) . Phitsanulok Province: Phu Hin Rongkla Natl. Park, stream btw Rd 2113 and Man Daeng Waterfall , 12.VI.1998, leg. R.W. Sites & K.B. Simpson, L-187, 22 males, 17 females ( UMC) ; same locality except for, Waterwheel falls and stream, 16°59'N 101°00'E, 1280 m a.s.l., 10.II.2003, leg. CMU Team, 6 males, 4 females ( UMC) ; same locality except for, 6.V.2003, leg. A. Vitheepradit, T. Prommi & M.L. Ferro, L-506, 2 males, 3 females ( UMC) ; same locality except for, 12.VII.2003, leg. N. Changthong, 1 male, 3 females ( UMC) ; Thung Salaeng Luang Natl. Park, Tum Din Stream, Ban Mung Subdistrict , Noen Maprang District , 16°29'07.5"N 100°48'31.2"E, 894 m a.s.l., 23.III.2011, leg. N. Sangpradub, 1 male, 1 female ( KKU) .

Diagnosis. Male ( Fig. 1B ): Size: 4.0–5.0 mm. Body form oval, strongly convex in lateral view; pronotum and elytral margins darkly colored, pronotum with median transverse depression ( Fig. 2A ), dorsal surface strongly iridescent, without evident microreticulation; pronotum and elytra laterally without bronzy-metallic sheen; striae I–XI evident with distinct, widely spaced punctures, striae VI–X strongly sulcate ( Fig. 2B ); elytral intervals VII–X convex; elytral apex truncate ( Figs. 1B , 2B–C ), without border ( Fig. 2C ), epipleural angle indistinct; metaepisternal ostiole small; aedeagus with median lobe slightly shorter than parameres, apical half of median lobe broader in width than single paramere, apex weakly triangular, lateral margin of parameres weakly curved, apex rounded ( Figs. 3C–D ).

Female: Similar to male but with a more oval body form; gonocoxae as in Fig. 3E .

Differential diagnosis. Among the Old World Gyrinus , G. smaragdinus is closest to G. ignitus Régimbart, 1895 , a Malagasy endemic species. The only other species of Gyrinus recorded from Thailand is G. sericeolimbatus . G. smaragdinus can be distinguished from G. sericeolimbatus by its iridescent appearance and strongly sulcate lateral elytral setriae.

Distribution. This species is known from northeastern India, to Myanmar, Yunnan Province of southern China, and northern Vietnam ( Ochs 1930; Vazirani 1972, 1984; Mazzoldi 1995). It is here recorded for the first time in Thailand.

Habitat. We found G. smaragdinus most often on stagnant water of montane streams and ponds at high elevation, ranging from 700 to 1600 m a.s.l. ( Figs. 7A–B ). Only a few specimens were found in a stream at a low elevation (270 m a.s.l.).

Discussion. G. smaragdinus is the only species of Gyrinus that we encountered during our sampling in the northern, western and northeastern regions of Thailand ( Fig. 8A ). The first author found this beetle in a pond surrounded by land with both agricultural use and intact forest.

Figures

FIGURE 1. Habitus of Gyrinini and Dineutini species: (A) Gyrinus sericeolimbatus, dorsal view, female; (B) G. smaragdinus, dorsal view, male; (C–D) Dineutus australis, dorsal view: (C) male; (D) female; (E) D. sitesi, dorsal view, male; (F) D. spinosus, dorsal view, male; (G) D. unidentatus, dorsal view, male; (H) Porrorhynchus marginatus, dorsal view, male; (I) D. sitesi, ventral view, male; (J) D. spinosus, ventral view, male. Scale bars = 3 mm.

FIGURE 2. Gyrinus smaragdinus: (A) female pronotum, median transverse depression (arrow), scale bar = 300 μm; (B) male elytra, spaced puncture (arrow), scale bar = 1 mm; (C) male elytral apex, scale bar = 300 μm.

FIGURE 3. Aedeagus and gonocoxae: (A–B) Gyrinus sericeolimbatus: (A) aedeagus, dorsal view (after Svensson 1991; Mazzoldi 2010); (B) gonocoxae, ventral view, scale bars = 0.5 mm; (C–E) Gyrinus smaragdinus: (C–D) aedeagus, scale bars = 0.5 mm: (C) dorsal view; (D) lateral view; (E) gonocoxae, ventral view, scale bars = 0.5 mm.

FIGURE 7. Habitats of species of Gyrinini and Dineutini: (A–B) G. smaragdinus: (A) stream at Siriphum Waterfall, Doi Inthanon Natl. Park, Chiang Mai Province; (B) pond at Ban Buak Thoei, Chiang Mai Province; (C) D. australis, D. spinosus and D. unidentatus, pond at Sakaerat Environmental Research Station, Nakhon Ratchasima Province; (D) D. sitesi, Tum Din Stream, Thung Salaeng Luang Natl. Park, Phitsanulok Province; (E) D. spinosus, Huay Sae Stream, Ubon Ratchathani Province; (F–G) D. unidentatus, ponds at Ban Kho, Khon Kaen Province; (H) P. marginatus, Lam Takong Stream, Nakhon Ratchasima Province.

FIGURE 8. (A–B) Distributions of species of Dineutini and Gyrinini in Thailand.