Neobidessodes darwiniensis, Hendrich, Lars & Balke, Michael, 2011

Hendrich, Lars & Balke, Michael, 2011, A simultaneous journal / wiki publication and dissemination of a new species description: Neobidessodes darwiniensis sp. n. from northern Australia (Coleoptera, Dytiscidae, Bidessini), ZooKeys 79, pp. 11-20 : 14-15

Neobidessodes darwiniensis sp. n. Figs 15, 6, 7

Type locality.

Rest pool, Harriet Creek at Kakadu Highway, 11 km NE Pine Creek, Northern Territory, Australia [13°45'04.63"S, 131°53.5531"E].

Type material.

Holotype: Female, "Australia: NT, Kakadu Hwy, Harriet Creek at Hwy Cross., 156m, 24.VIII.2006, 13.744816S, 131.897483E, L. & E. Hendrich leg. (NT 14)"; "DNA M. Balke 3821" [green printed label]; "HOLOTYPE Neobidessodes darwiniensis sp. n. Hendrich & Balke 2010" [red printed label] (SAMA).

Description.

Measurements. TL = 1.95 mm, TL-H = 1.8 mm; MW = 1.0 mm.

Colour.

Antennae, palpi, head and most parts of pronotum reddish-brown, posterior angles of head, near eyes and base of pronotum in middle broadly dark brown. Elytron dark brown with some small vague yellow spots subbasally and subapically (Fig. 1). Ventral side, including legs and epipleura, reddish-brown, prosternal process and metacoxal plates somewhat darkened.

Sculpture and structure.

Elongate oval, sides well rounded. Maximum width at apical third of body. Segments of antennae short and stout. Head with relatively coarse punctures and strong microreticulation. Pronotum and elytron with rather dense, medium-sized punctures and weak to moderate microreticulation, finely pubescent. Pronotal striae deep and well marked, length almost 1/2 of that of pronotum, strongly incurved converging anteriad (Fig. 1). Elytra lacking basal and sutural striae. Underside with a few moderately large weak punctures at sides, midline of metaventrite with moderately dense smaller punctures. Metacoxal lines raised, well separated, weakly diverging anteriorly.

Male.

Unknown.

Female.

Pro- and mesotarsi simple. Inner edge of mesotibia nearly straight.

Affinities - DNA Sequence Data.

The 3' cox1 sequence available at http://www.ncbi.nlm.nih.gov/nuccore/FR733592. 1 indicates that the new species is rather distinctive, the closest uncorrected p-distances in our database were other Neobidessodes species (c. 10.37%) and Limbodessus jundeensis (10.15%).

Morphology.

The smallest species of the genus. On first view, the new species resembles in size and colour the common Hydroglyphus godeffroyi (Fig. 4) distributed all over northern Australia and New Caledonia, and can be easily overlooked in the field. When recognized as a Neobidessodes the new species is similar to Neobidessodes mjobergi (Fig. 3) in coloration and to Neobidessodes bilita (Watts, 1978) (Fig. 2) in size. From Neobidessodes mjobergi it can be separated by its more broadly oval body, the much smaller size ( Neobidessodes mjobergi 2.55-2.65 mm) and unicolourus head, and from Neobidessodes bilita by the darker dorsal surface, the short and stout segments of antennae, the rounded, broadly oval body, and the unflanged subapical part of the elytra (Figs 1, 2). Furthermore, Neobidessodes bilita is a strictly south-eastern species with a disjunct distribution from southern Queensland to Victoria ( Hendrich et al. 2009).

Etymology.

Named after the Darwin area in the Northern Territory; the specific epithet is an adjective in the nominative singular.

Distribution.

Only known from the type locality at Harriet Creek, 11 km NE Pine Creek but probably more widespread in the Northern Territory (Fig. 5).

Habitat.

The single specimen was collected in one of the rest pools of a rocky creek, with gloomy water and at least partly shaded by smaller gum trees. The bottom consisted of coarse sand with a thick layer of unrotten leaves and twigs, no submerged or emergent vegetation visible (Figs 6, 7).

Neobidessodes darwiniensis sp. n. was associated with the dytiscids Clypeodytes larsoni Hendrich & Wang, 2006, Hydroglyphus daemeli (Sharp, 1882), Hydroglyphus godeffroyi , Hydroglyphus grammopterus (Zimmermann, 1928), Hyphydrus contiguus Wehncke, 1877, Hydroglyphus lyratus Swartz, 1808, Laccophilus cingulatus Sharp, 1882, Laccophilus sharpi Régimbart, 1889, Laccophilus walkeri J. Balfour-Browne, 1939, Limbodessus compactus (Clark, 1862), Neobidessodes grossus (Zimmermann, 1922), Neobidessodes mjobergi , Neobidessodes thoracicus Hendrich & Balke, 2009, Sternopriscus alligatorensis Hendrich & Watts, 2004, Sternopriscus aquilonaris Hendrich & Watts, 2004, Tiporus centralis (Watts, 1978), Tiporus guiliani (Watts, 1978) and Tiporus undecimmaculatus (Clark, 1862).

Remarks.

Despite the fact that thousands of Neobidessodes were collected on three field trips to the Northern Territory and the Kimberley region, surprisingly only one specimen of Neobidessodes darwiniensis sp. n. appeared. Most of the expeditions took place during the dry period, between June and October, when most of the other species of the genus dominate the remaining rest pools and swamps. We assume the new species is more common in or just after the rainy season, from November to April, as was observed for Neobidessodes grossus ( Hendrich et al. 2009).