Exocelina mimika 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 mimika Shaverdo & Balke sp. nov. Figs 5 , 8 , 9

Type locality.

Indonesia: Papua Province, Mimika Regency, Tsinga Village, Beanekogom River, 04°11.629'S, 137°13.756'E, 1690 m a.s.l.

Type material.

Holotype: male "Indonesia: Papua, Kabupaten [Regency] Mimika, Desa [Village] Tsinga, Sungai [River] Beanekogom,", "1690m, 25-30.v.2017, 04°11.629'S, 137°13.756'E, B. Sumoked (Pap66-Bob04)" (MZB). Paratypes: 3 males with the same label as the holotype (KSP, MZB).

Description.

Body size and form: Beetle medium-sized: TL-H 4.8-5.0 mm, TL 5.2-5.4 mm, MW 2.5-2.6 mm (holotype: TL-H 4.8 mm, TL 5 mm, MW 2.5 mm), with oblong-oval habitus (Fig. 8 ).

Colouration: Dorsally piceous (Fig. 8 ), sometimes with dark brown posterior part of head, lateral sides of pronotum, and dark brown elytral sutural lines; head appendages yellowish brown, legs yellowish brown to reddish-brown. Teneral specimens paler.

Surface sculpture: Shiny dorsally, with distinct punctation and weakly impressed microreticulation. Head with relatively dense, unevenly distributed punctation (spaces between punctures 1-4 times size of punctures), distinctly finer and sparser anteriorly and posteriorly; diameter of punctures equal to diameter of cells of microreticulation. Pronotum and elytra with punctation sparser and finer than on head and with distinct but weakly impressed microreticulation; head with stronger microreticulation. Metaventrite and metacoxae distinctly microreticulate, metacoxal plates with longitudinal strioles and transverse wrinkles. Abdominal ventrites with distinct microreticulation, strioles, and fine but distinct punctation.

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

Male: Antenna simple. Pro- and mesotarsomeres 1-3 very slightly dilated. Protarsomere 4 simple, narrow, with large, thick, strongly curved anterolateral hook-like seta. Protarsomere 5 ventrally with anterior band of more than 50 and posterior row of 20 relatively long setae (Fig. 9D ). Median lobe robust, with continuous outline and without setation; lateral margins thick in apical half; apex with very short blunt prolongation in lateral view and deeply concave in ventral view (Fig. 9A, B ). Paramere without dorsal notch and with reduced setation: setae very thin, inconspicuous, sparse, longer subdistally and proximally and very short medially (Fig. 9C ). Abdominal ventrite 6 broadly rounded, with 2-7 lateral striae on each side.

Female: Unknown.

Habitat.

The specimens were collected from rock pools at the edge of a fast-flowing mountain stream.

Distribution.

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

Etymology.

The species is named after Mimika Regency, where it was collected. The name is a noun in the nominative singular standing in apposition.

Affinities and introduction of the E. skalei group.

The other Exocelina species known from the Tsinga area is E. tsinga Shaverdo et al., 2020, which is very similar to the new species in size, body shape, colouration, and surface sculpture. The males of these species can be easily distinguished due to the modified antennae of E. tsinga and different shape and setation of their genitalia; female identification, however, could be problematic.

Based on morphological characters, we cannot place the new species in any known species group. The new species resembles representatives of the E. jaseminae group in the shape of the median lobe and E. mekilensis Shaverdo & Balke, 2019 and species of the E. ullrichi group ( Shaverdo and Balke 2014) in the reduced setation of the paramere. However, in the shape of the median lobe and setation of the paramere, the new species is the most similar to E. skalei . Thus, we assume that these two species might be closely related. Exocelina skalei has been so far treated as a member of the E. ekari group but according to the molecular analyses, it is the sister clade of the E. ekari group ( Toussaint et al. 2014, 2015).

Therefore, for E. skalei and E. mimika sp. nov., herein we introduce a new species group, the E. skalei group, with the following diagnostic characters:

beetle small or medium-sized (TL-H 2.9-5.0 mm), with continuous body outline of broadly oval or oblong-oval shape;

elytra without striae/strioles, with distinct punctation, beetles shiny or submatt;

pronotum with distinct lateral bead;

antennomeres not modified;

male protarsomere 4 simple, with medium-sized or large, slightly or strongly curved anterolateral hook-like seta;

median lobe of aedeagus without setation, with continuous or slightly discontinuous apically outline;

paramere without dorsal notch and with strongly reduced setation: setae very thin and sparse, some longer setae distinct subdistally; setae tiny, inconspicuous medially and proximally.

Since the southern slopes of the central range is a poorly studied area, we assume that more species of the E. skalei group await discovery. The new material, including its molecular analysis, would help to confirm group delimitation.

Figures

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

Figure 8. Habitus and colouration of Exocelina mimika sp. nov., holotype.

Figure 9. Exocelina mimika 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.