Hermatobates sanho, Le & Tran & Nguyen, 2024

Le, Thi Phuong Linh, Tran, Anh Duc & Nguyen, Thi Anh Nguyet, 2024, Marine bugs (Hemiptera: Heteroptera: Gerromorpha) from Vietnam, with description of a new species of Hermatobates (Hermatobatidae), Acta Entomologica Musei Nationalis Pragae 64 (1), pp. 67-78 : 68-74

Hermatobates sanho sp. nov.

( Figs 1–4 )

Hermatobates schuhi (provisional identification): POLHEMUS & POLHEMUS (2012): 232 and fig. 25 (record from Vietnam).

Type material. HOLOTYPE: J, VIETNAM: BǠ R ịA- VŨNG TǠU: Côn Đ ảo Archipelago , Hòn Bà Island, 08°38.617′N 106°33.227′E, 15.iv.2010, Tran A.D. et al. leg.,TAD1013 ( ZVNU) . PARATYPES: VIETNAM: 5JJ 9♀♀, same locality data as holotype (3JJ 7♀♀ in ZVNU, 2JJ 2♀♀ ZRC). Additional (non-type) material. VIETNAM: 29 nymphs, same locality data as holotype ( ZVNU).

Description. Size (mm). Males: length 3.75–4.40 (holotype: 4.10), maximum width 1.95–2.37 (holotype: 2.20). Females: length 3.55–3.70 mm, maximum width 1.90–1.98 mm.

Colour ( Figs 1 , 2 ). Body and legs covered with silvery pubescence. Ground colour of dorsum generally brown to dark brown, venter light brown to brown. Anterior part of head dark brown, posterior margin of head light brown forming indistinct light brown transverse band. Antennae generally brown to dark brown, basal two-thirds of segment I yellowish. Legs generally brown to light brown, except for mostly yellowish fore coxa, fore tibia and all trochanters.

Apterous male (holotype). Body fusiform, length about 1.86× greatest width across thorax (4.10: 2.20). Head length 0.26× greatest width across eyes (0.40: 1.50). Eyes small, eye width [= (head width – interocular width) / 2] about 0.24× interocular width (0.24: 1.02). Antenna: total length 0.81× body length; lengths of antennal segments I– IV: 1.10: 1.00: 0.60: 0.61; segment I 2.75× head length (1.10: 0.40), slightly thicker than segments II–IV; combined length of all antennal segments 0.81× total length of body (3.31: 4.10). Pronotum short, median length 0.42× eye width (0.10: 0.24); posterior margin curved backward laterally and straight in middle. Meso- and metanotum simple. Metasternum with isosceles trapezoidal process on posterior margin ( Figs 3D , 4A–C ); ratio of apical width to basal width of process 0.38; ratio of length to apical width of process 0.73; metasternal process with numerous, short, stout papillae and interspersed with a few long, pointed densely-packed tufts of setae ( Figs 4C–F ).

Lengths of leg segments (femur: tibia: tarsus I: tarsus II: tarsus III): fore leg: 1.90: 1.75: 0.07: 0.13: 0.30; middle leg: 2.40: 1.55: 0.16: 0.75: 0.55; hind leg: 2.73: 1.60: 0.15: 0.68: 0.61. Fore trochanter with small tooth near distal end ( Fig. 3B ). Fore femur incrassate, width 0.65, flexor side with long, spur-like black tooth at base, broad distally bifid black tooth before apex, and mostly regular row of 15 small black teeth between these large teeth ( Figs 3A, B ). Fore tibia nearly straight, on flexor margin: black tooth at basal curve, followed by black bifid tooth after basal curve, then by large, stout black tooth in basal third, and low, broad black tooth in distal third; depression between large tooth (int basal third) and bifid tooth as wide as depression on bifid tooth; row of small black denticles from distal two-thirds towards apex of tibia ( Figs 3A, B ). Middle trochanter with slender and black spine distally. Middle femur thickened in middle (width 0.30), flexor side with eight spatulate, paddle-like spines in basal half, followed by ca. 10 almost straight stout spines ( Fig. 3C ). Hind femur slightly thickened in centre (width 0.38), trochanter and femur simple, without spines.

Abdomen short, length from abdominal scent orifice to tip 0.85, lengths of abdominal terga IV–VII: 0.09: 0.13: 0.21: 0.32. Genitalia: large, length 0.79; styliform processes of abdominal segment VIII with hook-shaped apex and on inner surface of sub-apical part with a few long setae ( Figs 3E , 4G ); pygophore with triangular basal margin curved upwards; parameres plate-shaped, asymmetrical, left paramere smaller than right paramere.

Apterous female. Body fusiform, length about 1.89× body width (3.60: 1.90). Head length 0.28× head width across eyes (0.40: 1.45), eyes rather small, eye width 0.23× interocular width (0.23: 1.00). Antenna relatively shorter than in male, total length 0.66× body length (2.37: 3.60); lengths of antennal segments I–IV: 0.67: 0.75: 0.50: 0.45; segment IV about 1.12× head length (0.45: 0.40). Pronotum short, median length 0.43× eye width (0.1: 0.23); metasternum not modified.

Legs relatively shorter and slenderer than in male. Lengths of leg segments (femur: tibia: tarsus I: tarsus II: tarsus III): fore leg: 1.06: 1.03: 0.04: 0.08: 0.26; middle leg: 1.80: 1.04: 0.12: 0.54: 0.44; hind leg: 1.88: 1.04: 0.10: 0.54: 0.52. Fore trochanter simple, without spines. Fore femur thickened in middle (width 0.22) and with row of 16–18 small black teeth on flexor side. Fore tibia almost straight, without teeth. Middle trochanter simple, without spines. Middle femur thickened in middle (width 0.20) with row of 15–20 small black spines in basal two-thirds, among which first 6–9 spines in basal part of femur longer than distal ones (number of spines variable among individuals). Hind femur slightly thickened in middle (width 0.16), without spines.

Abdomen length from abdominal scent orifice to apex: 0.92; lengths of abdominal terga IV–VII: 0.14: 0.20: 0.25: 0.26. Abdominal sterna II–VII forming large sub- -rectangular plate, length 0.61, posterior margin slightly produced medially. Genital segments concealed by sternal plate, except for apically-rounded proctiger.

Comparative notes. Hermatobates sanho sp. nov. belongs to the H. weddi species group sensu POLHEMUS & POLHE- MUS (2012), as the male has a well-developed metasternal process with papillae and fore tibia with multiple teeth in the basal part (one bifid tooth and a large tooth or two sub- -basal teeth and a large tooth). Within this species group, H. sanho sp. nov. is most similar to H. weddi China, 1957 (widespread from the seas of the Lesser Sunda Islands and western Australia to Polynesia), H. schuhi Polhemus & Polhemus, 2012 (from Ryukyu Islands), and H. lingyangjiaoensis Luo, Chen & Wang, 2019 (from Paracel Islands) in having (in the male) an isosceles trapezoidal metasternal process (which is situated on the posterior margin of the metasternum and sloping towards the base of genitalia) and fore tibia with either one bifid tooth or two sub-basal teeth followed by a large tooth.

The new species can be separated from these species mentioned above, based on the set of the following characteristics. The general shape and morphometric ratios of the metasternal process of H. sanho sp. nov. are more similar to that of H. weddi than to that of the other two species. However, the papillae pattern in H. sanho sp. nov. is distinctly different from that in H. weddi , H. schuhi , and H. lingyangjiaoensis . In H. sanho sp. nov., there are a few long, slender, and pointed densely-packed tufts of setae (which appear to have a similar structure as papillae but are of smaller diameter) scattered and interspersed with short and stout papillae (which are more densely situated). In H. weddi , there are only a few scattered, large papillae; in H. lingyangjiaoensis , there are only a few scattered, smaller papillae. In H. schuhi , there are also numerous, densely-situated short and stout papillae, and very few long, slender, and pointed densely packed tufts of setae, but these tufts are restricted to the base of the metasternal process.

The armature in the basal part of the male fore tibia of H. sanho sp. nov. is more similar to that of H. lingyangjiaoensis than to those of H. weddi and H. schuhi . In both H. weddi and H. schuhi , the flexor margin of the basal part of male fore tibia has a broad, bifid tooth (which is referred to as “protuberance” in POLHEMUS & POLHEMUS (2012) and LUO et al. (2019)), followed by a depression, which is about as wide as or wider than the width of the bifid tooth, then a large stout tooth (which was referred to as “tubercle” in POLHEMUS & POLHEMUS (2012) and LUO et al. (2019)). In both H. sanho sp. nov. and H. lingyangjiaoensis , in the basal part of the male fore tibia, there are two round sub-basal teeth, which are clearly separated from each other by a shallow depression, then followed by a depression and a large, stout tooth distally. However, in H. sanho sp. nov., the depression from the second sub-basal tooth (the first one is the nearer to the base of the tibia) to the large stout tooth is wider than the depression between two sub-basal teeth, while in H. lingyangjiaoensis , the depression between the second sub-basal tooth and the large stout tooth is distinctly narrower than the depression between two sub-basal teeth.

The styliform process of the male abdominal segment VIII of H. sanho sp. nov. is very similar to that of H. weddi in having a short, somewhat hook-shaped apex and the inner surface of the sub-apical part with a few long setae (cf. POLHEMUS & POLHEMUS 2012: fig. 6B). This structure is clearly different in H. schuhi and H. lingyangjiaoensis . In H. schuhi , the apex is longer, curved at approximately 90° and the inner surface of sub-apical part has more setae (see POLHEMUS & POLHEMUS 2012: fig. 6A). In H. lingyangjiaoensis , the apex of the styliform process is less developed, shorter, and sub-triangular (see LUO et al. 2019: figs 17–19).

Other structural differences between H. sanho sp. nov., H. weddi , H. schuhi , and H. lingyangjiaoensis include the type and number of spines on the male middle femur and the female middle femur.

The male middle femur of H. sanho sp. nov. has a row of ca. 20 spines on the flexor side, including eight spatulate, paddle-like spines in the basal half, then followed by ca. 10 almost straight stout spines in the distal part, and a few shorter spines. Whereas, in H. weddi , the male middle femur has a row of ca. 20 spatulate, paddle-like spines; in H. schuhi , it has 20–24 almost straight stout spines along the flexor side, some near the base are with hooked tips; in H. lingyangjiaoensis , it has at least 24 spines, of which only 4–6 spatulate, paddle-like spines are in basal third, followed by slenderer and straight spines distally.

The female middle femur of H. sanho sp. nov. has 15–20 small spines on the flexor side, while that of H. schuhi has around seven small spines, and that of H. lingyangjiaoensis has around 12 small spines. The female middle femur of H. weddi has only a few tiny, barely visible black teeth basally. The morphological comparison of the species of H. weddi species group is summarised in Table 1 below.

Etymology. The epithet sanho is from the Vietnamese words “san hô”, meaning corals, with reference to the typical habitat of Hermatobates , which are intertidal coral reef flats.

Habitat. Specimens of H. sanho sp. nov. were collected at night, during low tide on an intertidal reef flat at Côn Đảo Archipelago, approximately 85 km off the coast of southern Vietnam. The reef flat is characterized by a combination of corals, small rocks and sandy bottom. The specimens were observed either resting on edge of the shallow intertidal pools ( Fig. 1 ) or moving swiftly between these pools.

Distribution. Vietnam: Côn Đảo. POLHEMUS & POLHEMUS (2012: 232 and fig. 25) referred to a provisional record of H. schuhi from Vietnam which relied on the correspondence with the second author of the present paper (Tran A.D.). This reference is indeed based on the same specimens which are now formally determined as H. sanho sp. nov.

Figures

Fig. 1. In-situ photographs of Hermatobates sanho sp. nov.A–B – a female resting on the edge of an intertidal pool, side view and top view. C – a nymph feeding on a small crustacean prey and resting on emerged hard coral during low tide.

Fig. 2. Habitus of Hermatobates sanho sp. nov., male.

Fig. 3. Morphological features of Hermatobates sanho sp. nov., male. A–B – right fore leg (A – dorsal view, B – ventral view), C – middle femur, D – ventral view showing metasternum, E – styliform processes of abdominal segment VIII.

Fig. 4. Scanning electron micrographs of morphological features of Hermatobates sanho sp. nov., male. A–D – metasternal process at different magnifications; E–F – papillae on metasternal process at different magnification; G – styliform process of abdominal segment VIII.