Exocelina baliem, Shaverdo, Helena V., Hendrich, Lars & Balke, Michael, 2013

Shaverdo, Helena V., Hendrich, Lars & Balke, Michael, 2013, Exocelina baliem sp. n., the only known pond species of New Guinea Exocelina Broun, 1886 (Coleoptera, Dytiscidae, Copelatinae), ZooKeys 304, pp. 83-99 : 84-88

Exocelina baliem sp. n. Figs 1-7

Type locality.

Indonesia: Papua Province: Jayawijaya Regency, Baliem River Valley, Wamena, 138°56'E, 04°06'S.

Type material.

Holotype: male "IRIAN JAYA Baliem-Tal Wamena, 1700 m 138°56'E, 04°06'S", “20– 27.9.1992 (54A = 57) leg. M. Balke" (NHMW). Paratypes: 2 males, 3 females with the same label as the holotype, 1 female additionally with two green labels “DNA”, "M.Balke 3268" (NHMW, ZSM). 1 male "W.-Neuguinea/Baliem Valley Wamena (Ort), 1600m / IR 1&6 31.8 & 6.9.1990 leg: Balke & Hendrich", "Coll. Hendrich Berlin" (CLH). 1 female "IRIAN JAYA, Jayawijaya-Prov., leg. A.Riedel, 1993", "Wamena, Baliem-River, 1700m, 15.X." (ZSM).

Diagnosis.

Beetle middle-sized, piceous, with reddish brown head; both sexes matt, dorsal surface with strong dorsal microreticulation and numerous, short strioles; male antennomeres simple; male pro- and mesotarsomeres 1-3 distinctly dilated, male protarsomere 4 modified, with large, thick anterolateral hook-like seta, male protarsomere 5 simple, with relatively long setae and long claws, anterior claw with fine serration ventrally; median lobe with continuous outline in ventral view, ventral sclerite with a strip of sclerotization on right side, proximal part of median lobe striolate; paramere without notch on dorsal side but with a long prolongation of subdistal part; female metatarsi without ventral row of natatorial setae; gonocoxae with prolonged, slightly pointed apices. This is the only New Guinea species of Exocelina with a striolate dorsal surface.

Description.

Size and shape: Beetle middle-sized (TL-H 4.2-4.5 mm, TL 4.7-5.1 mm, MW 2.2-2.3 mm), one female larger (TL-H 4.9 mm, TL 5.5 mm, MW 2.4 mm), with elongate habitus, broadest at elytral middle; pronotum relatively long (width of pronotum/length of pronotum ratio 0.4), only slightly trapezoidal, with sides weakly converging forwards, with posterior angles not drawn backwards (Fig. 1). Coloration: Head reddish brown, with darker, indistinct, broad, V-shaped median spot and dark brown posteriorly to eyes; pronotum piceous, with anterior margin and anterior angles reddish brown to brown; elytra piceous, sometimes with paler (reddish brown to dark brown) posterolateral sides, apex, and narrow bands along elytral suture; head appendages yellowish to reddish-brown, hind legs darker; ventrally reddish brown, with piceous metaventrite and metacoxal plates.

Surface sculpture: Head with dense, coarse punctures (spaces between punctures 1-3 times size of punctures, diameter of punctures much larger than diameter of cells of microreticulation) on middle, anterior part of head with finer punctation, between and behind eyes with very short but distinct longitudinal strioles, vertex with fine, sparse punctation. Pronotum with numerous short longitudinal strioles, distinctly shorter and sparser on disc, disc also with coarse punctures. Elytra densely covered with numerous short longitudinal strioles, posterior third of elytra with transverse shackle-like strioles, and elytral lateral margins with transverse strioles and coarse punctures. Head, pronotum, and elytra with strongly impressed microreticulation, dorsal surface matt. Metaventrite and metacoxa distinctly microreticulate. Metacoxal plates densely covered with short longitudinal strioles and in anterior part also with transverse wrinkles. Abdominal ventrites with finer microreticulation and fine sparse punctation, more evident at their middle. Ventrites 1-2 with numerous longitudinal striae, ventrites 3-5 with finer, shorter, transverse strioles, and ventrite 6 with long sublongitudinal strioles.

Structures: Pronotum with distinct lateral bead. Base of proste rnum and neck of prosternal process with distinct ridge, without anterolateral extensions. Blade of prosternal process lanceolate, relatively broad, convex, with distinct bead and very few fine setae; neck and blade of prosternal process evenly jointed. Abdominal ventrite 6 broadly rounded apically.

Male: Antennomeres simple. Pro- and mesotarsomeres 1-3 distinctly dilated. Protarsomere 4 asymmetrical, its anterior angle expanded with large, thick, strongly curved anterolateral hook-like seta. Protarsomere 5 simple, ventrally with anterior row of 17-18 and posterior row of 4 long setae; pro- and mesotarsal claws long (length of anterior claw/length of protarsus ratio 0.7), posterior protarsal claw evenly curved, with two fine denticles on ventral margin; anterior claw longer, straighter, and slightly broadened, with fine serration ventrally (Figs 2A, 3A). Abdominal ventrite 6 with 20-25 lateral striae on each side. Median lobe with continuous outline, slightly asymmetrical in ventral view; apex of median lobe swollen in lateral view and roundly pointed in ventral view, ventral sclerite with a strip of sclerotization on right side in ventral view, proximal part of median lobe striolate (Figs 5A, 6). Paramere without notch (for comparison, e.g. see Figs 1-4 in Shaverdo et al. 2012) but with a long prolongation on subdistal part of dorsal side (Fig. 4A).

Female: Dorsal microreticulation stronger, abdominal ventrite 6 without or with 1-2 very fine median striae. Metatarsi without ventral row of natatorial setae. Gonocoxosternites similar to those of Exocelina vladimiri Shaverdo, Sagata & Balke, 2005 (see Fig. 17a in Shaverdo et al. 2005). Gonocoxae with prolonged, slightly pointed apices and sparse setation, without setae on inner margin in ventral view (Fig. 7A).

Distribution and habitat.

The species is known only from the type locality (Fig. 8).

The species was collected from a small pool in a riverine relic forest close to the Baliem River, approximately 1 km from the runway of Wamena airport (Fig. 9). The beetles were found between roots, leaves, and emergent water plants in the shallow water, at the shady edge of the pond underneath a large tree. One specimen was collected from a tuft of Phragmites after the pool had dried up during the rather dry summer in the following year (1993). The new species was associated with the following dytiscids: Hydrovatus enigmaticus Biström, 1997, Hyphydrus dani Biström, Balke & Hendrich, 1993, Hydaticus okalehubyi Balke & Hendrich, 1992, and Rhantus dani Balke, 2001. We revisited the area in winter 2011 and found that most ponds were highly eutrophic (as foreseen by Balke 1993), large trees had mostly disappeared, and the species was not found again during a quick survey. We assume that the type locality has been destroyed, but other suitable habitats might exist elsewhere in the vast valley.

Etymology.

The species is named after the type locality, the Baliem River Valley. The name is a noun in the nominative singular standing in apposition.