Exocelina brazza Shaverdo & Balke, 2020

Shaverdo, Helena, Surbakti, Suriani, Sumoked, Bob & Balke, Michael, 2020, Three new species of Exocelina Broun, 1886 from the southern slopes of the New Guinea central range, with introduction of the Exocelina skalei group (Coleoptera, Dytiscidae, Copelatinae), ZooKeys 1007, pp. 129-143 : 129

Exocelina brazza Shaverdo & Balke sp. nov. Figs 1 , 2 , 3 , 4 , 5

Type locality.

Indonesia: Papua Province, Yahukimo Regency, Dekai, upper Brazza River, near 04°44'27.9"S, 139°39'15.2"E, 300 m a.s.l.

Type material.

Holotype: male "Indonesia: Papua, Dekai, upper Brazza, 300 m, 2/3.vi.2015, near -4,741084724 139,654211075976, Sumoked (Pap045)" (MZB). Paratypes: 2 males, 10 females with the same label as the holotype, one male and one female additionally with green text labels “6991” and “6990”, respectively (KSP, MZB).

Description.

Body size and form: Beetle small: TL-H 3.05-3.3 mm, TL 3.45-3.7 mm, MW 1.65-1.8 mm (holotype: TL-H 3.3 mm, TL 3.7 mm, MW 1.8 mm), with oblong-oval habitus (Fig. 1 ).

Colouration: Dorsally brown, with reddish pronotal sides (Fig. 1 ). Head reddish in anterior half (in front of eyes) and reddish-brown to brown in posterior half (at eye level and behind); pronotum reddish-brown on disc and with broad reddish sides, sometimes also reddish along anterior and posterior margins; elytron reddish-brown to dark brown, with reddish sutural lines; head appendages yellow to yellowish-red, legs reddish. Teneral specimens paler.

Surface sculpture: Shiny dorsally, with fine punctation and microreticulation. Head with dense punctation (spaces between punctures 1-3 times size of punctures), distinctly finer and sparser anteriorly and posteriorly; diameter of punctures smaller than diameter of cells of microreticulation. Pronotum with distinctly finer and relatively sparser punctation than on head. Elytra with very sparse and fine punctation, almost invisible. Pronotum and elytra with weakly impressed microreticulation; head with stronger microreticulation. Metaventrite and metacoxa distinctly but weakly microreticulate, metacoxal plates with longitudinal strioles and transverse wrinkles. Abdominal ventrites with weak microreticulation, strioles, and fine sparse punctation, coarser and denser on two last abdominal ventrites.

Structures: Pronotum with distinct lateral bead. Base of prosternum and neck of prosternal process with ridge, slightly rounded anteriorly. Blade of prosternal process broadly lanceolate, relatively broad and short, slightly convex medially, with distinct bead and few setae. Abdominal ventrite 6 broadly rounded apically.

Male: Antenna modified: antennomeres 3-4 strongly enlarged, antennomere 5 distinctly enlarged and antennomeres 6-10 stout (Fig. 1 ). Pro- and mesotarsomeres 1-3 not dilated. Protarsomere 4 cylindrical, narrow, with large, thick, strongly curved anterolateral hook-like seta. Protarsomere 5 ventrally with anterior row of 12 and posterior row of 5 short setae (Fig. 2D ). Median lobe with discontinuous outline and distinct submedian constriction in ventral view; apex elongate in lateral view (Fig. 2A, B ). Paramere without distinct dorsal notch; subdistal part with relatively long, dense setae; proximal setae inconspicuous (Fig. 2C ). Abdominal ventrite 6 broadly rounded, with 10-14 lateral striae on each side.

Female: Pro- and mesotarsi not modified. Abdominal ventrite 6 without striae.

Habitat.

The specimens were collected from a small creek on an almost flat primary forest floor, about 100 m from the upper Brazza River (Figs 3 , 4 ).

Distribution.

Indonesia: Papua Province. This species is known only from the type locality (Fig. 5 ).

Etymology.

The species is named after the Brazza River. The name is a noun in the nominative singular standing in apposition.

Affinities.

The species evidently belongs to the E. ekari group due to the discontinuous outline of its median lobe. Within the group, it can be placed close to the shiny species with antennomeres 3 and 4 larger than other antennomeres (including the recently described E. athesphatos Shaverdo et al., 2020 and E. tsinga Shaverdo et al., 2020), to which it is assumed to be closely related. However, E. brazza sp. nov. can be easily distinguished from all of them by its small size, shape of the male antennae, median lobe and paramere.

Figures

Figure 1. Habitus and colouration of Exocelina brazza sp. nov., holotype.

Figure 2. Exocelina brazza sp. nov., paratype A median lobe in ventral view B median lobe in lateral view C right paramere in external view D right male protarsomeres 4 - 5 in ventral view.

Figure 3. Habitat area of Exocelina brazza sp. nov., a view from the forest down into Brazza River.

Figure 4. Habitat of Exocelina brazza sp. nov., a small creek in the primary forest, ca 100 m from the Brazza River.

Figure 5. Map of the western part of New Guinea showing the species distribution.