Nagisavelia hikarui Watanabe, Nakajima et Hayashi, 2023

Watanabe, Kohei, Nakajima, Jun & Hayashi, Masakazu, 2023, Nagisavelia hikarui, a new genus and species of Mesoveliinae (Hemiptera: Heteroptera: Mesoveliidae) inhabiting shingle beaches in Japan, Zootaxa 5353 (5), pp. 468-478 : 469-477

Nagisavelia hikarui Watanabe, Nakajima et Hayashi , sp. nov.

[Japanese name: Nagisa-Mizukamemushi]

( Figs. 1–8 , 11–24 )

Speovelia maritima (misidentification; nec Esaki, 1929): Hayashi 2007: 117 [partim, figs. 1, 3]; Wada & Yoshimatsu 2023: 15 [figs. 1–2].

Type material. HOLOTYPE: apterous male ( KMNH), Imazu , Nishi-ku, Fukuoka-shi, Fukuoka Prefecture, Japan, 25 V 2022, H. Nagano & J. Nakajima leg. PARATYPES: 2 apterous males, 10 apterous females ( KMNH, IIM) ,

same data as holotype; 4 apterous males, 2 apterous females ( KMNH, IIM, JNC) , same locality as holotype, 2 V 2023, J. Nakajima & H. Nagano leg.; 1 apterous male ( HOWP), Inome, Izumo-shi, Shimane Prefecture, Japan, 20 V 2006, M. Hayashi leg.; 2 apterous females ( HOWP), Hinomisaki (near Hinomisaki-todai), Taisha-cho, Izumo-shi, Shimane Prefecture, Japan, 28 VI 2006, M. Hayashi leg.; 1 apterous female ( HOWP), Hinomisaki (near Hinomisaki-todai), Taisha-cho, Izumo-shi, Shimane Prefecture, Japan, 20 VII 2006, M. Hayashi leg.; 1 apterous female ( HOWP), Nakayama, Hinomisaki, Taisha-cho, Izumo-shi, Shimane Prefecture, Japan, 20 VII 2006, M. Hayashi leg.; 1 apterous female ( HOWP), Owashi-hama , Himomisaki , Taisha-cho, Izumo-shi, Shimane Prefecture, Japan, 9 IV 2014, M. Hayashi leg.

Description. Apterous male ( Figs. 1, 3, 5 , 7 , 11–14 , 19–22 ). Coloration ( Figs. 1, 3, 5 , 7 ): Head royal-orange; labium royal-orange; antennal segment I–II light-royal-orange, segment III–IV lighter in color; eyes red; pro-, meso-, metanotum royal-orange; fore, middle, hind legs light-yellow, spines of hind tibia dark-red, claw yellowishbrown; abdomen royal-orange. Body ( Figs. 1, 3, 5 ): Length, 2.31–2.42 (mean ± SD = 2.38 ± 0.05); width, 0.77–0.82 (0.80 ± 0.02). Head ( Figs. 1, 3, 5 , 19 ): Parallel in middle, slightly narrow at base, length, 0.71–0.75 (0.73 ± 0.01); width (outsides of antennal socket distance), 0.38–0.39 (0.39 ± 0.00), 1.89–1.93 times as wide as long, interocular distance, 0.31–0.32 (0.31 ± 0.01), covered with many short hairs, two longitudinal gaps between hairs dorsally, meeting in the midline between eyes ( Fig. 19 ); three pairs cephalic trichobothria dorsally, one anterior pair inserted in front of antennal sockets, second pair inserted between antennal sockets and eyes, one posterior pair inserted at base of head; eyes each with approximately eight small ommatidia, with dense setae ( Fig. 21 ); antenna 0.83–0.84 times as long as body, antennal segments I–II broader than III–IV, lengths of antennal segments I–IV as follows: I, 0.34–0.36 (0.35 ± 0.01); II, 0.43–0.46 (0.44 ± 0.01); III, 0.41–0.46 (0.44 ± 0.02); IV, 0.71–0.74 (0.73 ± 0.01). Thorax ( Fig. 19 ): Bearing dense hairs, center depressed; pronotum broad, with impressed line from 1/4 of anterior margin to middle of posterior margin, collar present on anterior margin, length in middle, 0.21; width, 0.56–0.57 (0.56 ± 0.00), 2.64–2.77 times as wide as long; mesonotum, length in middle, 0.14–0.16 (0.15 ± 0.01); width, 0.62, 4.31–4.37 times as wide as long; metanotum, length in middle, 0.09; width, 0.66–0.67 (0.66 ± 0.00), 7.25–7.61 times as wide as long; pronotum longest and narrowest, metanotum shortest and broadest; middle thoracic venter with grooves. Legs: covered with many short hairs, femur broadest, posterior margin concave near apex, tibial apex densely hairy; fore- and middle legs simple; hind tibia with sparse spines dorsally and laterally, with some spines at posterior ventral apex; femur, tibia, and tarsus (tarsomere I–III) lengths: fore leg: 0.65–0.71 (0.68 ± 0.03), 0.56–0.58 (0.57 ± 0.01), 0.05, 0.07, and 0.11–0.12 (0.11 ± 0.00), respectively; middle leg: 0.68–0.71 (0.70 ± 0.01), 0.66–0.70 (0.68 ± 0.02), 0.04–0.06 (0.05 ± 0.01), 0.07–0.08 (0.08 ± 0.00), and 0.11–0.13 (0.12 ± 0.01), respectively; hind leg: 0.93–0.97 (0.95 ± 0.02), 0.99–1.02 (1.01 ± 0.01), 0.05, 0.09, and 0.13–0.15 (0.14 ± 0.01), respectively. Abdomen ( Fig. 20 ): Slightly narrow toward rear, covered with many short hairs; mediotergites slightly convex in center, segment I shortest, segments II–VI length subequal, VII longest, I–VII obviously wider than long, segment IV with a scent orifice in basal 2/5 ( Fig. 20 ); laterotergites broad and raised, outer margin rounded, segments IV–V widest. Genital segments ( Figs. 11–14 ): Segment VIII ( Fig. 11 ) about 1.05 times as long as wide, anterior margin almost straight, slightly narrower toward posterior, middle of posterior margin slightly depressed, covered with many light-brown hairs, dorsal length 1.8 times as long as ventral; pygophore ( Figs. 13–14 ) anterior margin almost straight, side slightly parallel, posterior margin rounded, row of setae across center dorsally ( Fig. 14 ), without hairs, posterior half of lateral and ventral with many light-brown hairs ( Fig. 13 ); left and right parameres symmetrical, triangular, projecting laterally, apex curved slightly forward, with sparse small setae at base dorsally ( Figs. 13–14 ); proctiger ( Fig. 12–13 ) with two pairs, small acuminate lateral projections, dorsal surface with sparse setae in center, posterior to lateral projections with many light-brown hairs.

Apterous female ( Figs. 2, 4, 6 , 8 , 15–18 , 23–24 ). Structures similar to those of apterous male. Body larger than that of male. Body: Length, 2.77–2.80 (2.77 ± 0.01); width, 0.94–1.02 (0.98 ± 0.03). Head: Length, 0.78–0.82 (0.80 ± 0.02); width, 0.41–0.43 (0.42 ± 0.01), 1.84–1.94 times as long as wide, interocular distance, 0.33–0.35 (0.34 ± 0.01); antenna 0.68–0.73 times as long as body, lengths of antennal segments I–IV as follows: I, 0.33–0.35 (0.33 ± 0.01); II, 0.45–0.47 (0.46 ± 0.01); III, 0.47–0.48 (0.47 ± 0.01); IV, 0.64–0.76 (0.75 ± 0.05); labium long, reaching posterior margin of abdominal sternum III to anterior of sternum IV. Pronotum: Length, 0.19–0.21 (0.21 ± 0.01); width, 0.62–0.63 (0.63 ± 0.01), 3.03–3.27 times as wide as long. Mesonotum: Length, 0.14–0.16 (0.15 ± 0.01); width, 0.68–0.70 (0.70 ± 0.01), 4.40–4.87 times as wide as long. Metanotum: Length, 0.09–0.10 (0.10 ± 0.00); width, 0.74–0.75 (0.74 ± 0.00), 7.63–8.02 times as wide as long. Legs: Femur, tibia, and tarsus (tarsomere I–III) lengths: fore leg: 0.63–0.66 (0.65 ± 0.01), 0.57–0.60 (0.57 ± 0.01), 0.05 (0.05 ± 0.00), 0.06 (0.06 ± 0.00), and 0.10–0.12 (0.11 ± 0.01), respectively; middle leg: 0.70–0.72 (0.71 ± 0.01), 0.70–0.72 (0.71 ± 0.01), 0.06 (0.06 ± 0.00), 0.06–0.07 (0.07 ± 0.00), and 0.11–0.13 (0.12 ± 0.01), respectively; hind leg: 0.92–0.96 (0.94 ± 0.02), 1.03–1.06 (1.04 ± 0.01), 0.06–0.07 (0.07 ± 0.00), 0.09–0.10 (0.09 ± 0.00), and 0.12–0.15 (0.14 ± 0.01), respectively. Abdomen: Mediotergites slightly convex in center, segment I shortest, VII longest, I–VIII obviously wider than long, segment IV with a scent orifice basal 2/5 ( Fig. 24 ); laterotergites broad and raised, outer margin rounded; ovipositor ensiform, both sides serrated from middle to apex ( Fig. 17 ); gynatrial sac coiled in shape ( Fig. 18 ); spermathecal tube, long, flexible, string-like ( Fig. 18 ).

Macropterous male and female. Unknown.

Etymology. The specific name is dedicated to Mr. Hikaru Nagano, the discoverer of this new species.

Distribution. Japan (Honshu, Shikoku, Kyushu).

Biology. This new species can be found in the intertidal zone on pebble to cobble deposits by digging in the gravel during low tide in the daytime ( Figs. 9–10 ). Although the adults are capable of walking on the water surface ( Fig. 7 ), the species has not been observed in tide pools or rock pools.

Remarks. Nagisavelia hikarui sp. nov., with eyes bearing dense hairs, inhabits the water edges of shingle beaches. This characteristic is also observed in Pseudovelia lasiomma Watanabe et Hayashi, 2023 (Veliidae) , which also has eyes with dense hairs, and inhabits the water edges of lakes ( Watanabe & Hayashi 2023). Thus, such eyes with dense hairs may have a certain advantage for inhabiting wave-splashed environments.

Nagisavelia hikarui sp. nov. is similar to Cavaticovelia aaa ( Gagné & Howarth, 1975) and Speovelia maritima , with respect to some morphological characteristics and habitat. Nagisavelia hikarui sp. nov. inhabits the water edges of shingle beaches, C. aaa inhabits lava tubes on the Hawaii Island ( Gagné & Howarth, 1975), and S. maritima inhabits sea caves and vertical wall surfaces ( Esaki, 1929). Gagné & Howarth (1975) suggested that the endemic Hawaiian species, C. aaa , was derived from a progenitor similar to S. maritima known from sea caves and rocky coasts in Japan. The similarities in character states among these three insular species may be an important lead to examine the hypothesis of Gagné & Howarth (1975). We expect that molecular phylogeographic methods will be useful in testing this hypothesis.

Figures

FIGURES 1–6. Nagisavelia hikarui sp. nov. 1, 3, 5, male; 2, 4, 6, female. 1, Holotype; 2–6, paratypes. 1–3, Dorsal aspect; 4, ventral aspect. 5–6, Live specimen. Scale refers to 1–4.

FIGURES 7–10. Nagisavelia hikarui sp. nov. and its type locality. 7, Adult male; 8, adult female; 9, type locality; 10, habitat.

FIGURES 11–14. Abdominal segment VIII, pygopore, and proctiger of Nagisavelia hikarui sp. nov. male, holotype. 11, Abdominal segment VIII, ventral view; 12, proctiger, dorsal view; 13, pygophore (segment IX) and proctiger, lateral view; 14, same, dorsal view. Scale bars = 0.05 mm.

FIGURES 15–18. Head, second gonocoxa, ovipositor and gynatrial complex of Nagisavelia hikarui sp. nov. female. 15, Head, ventral view; 16, second gonocoxa and gonoplac; 17, ovipositor (first gonapophysis), ventrolateral view; 18, gynatrial complex. Scale bars = 0.05 mm.

FIGURES 19–24. Scanning electron microscope (SEM) photographs of Nagisavelia hikarui sp. nov. 19–22, Male; 23–24, female. 19, 23, Head to abdomen; 20, thorax and abdomen, 21, eye, lateral view; 22, hind tibia and tarsus; 24, abdomen.