Exocelina saltusholmesensis, Watts, Chris H. S., Hendrich, Lars & Balke, Michael, 2016

Watts, Chris H. S., Hendrich, Lars & Balke, Michael, 2016, A new interstitial species of diving beetle from tropical northern Australia provides a scenario for the transition of epigean to stygobitic life (Coleoptera, Dytiscidae, Copelatinae), Subterranean Biology 19, pp. 23-29 : 24-26

Taxon classification Animalia Coleoptera Dytiscidae

Exocelina saltusholmesensis sp. n. Figs 1, 3

Type locality.

Small seasonal creek [-12.400714° 130.931297°], Holmes Jungle Reserve, Darwin, Northern Territory, Australia.

Type material.

Holotype, female (South Australian Museum Adelaide, SAMA): "Australia, Northern Territory, Darwin, Holmes Jungle Reserve, -12.400714° 130.931297°, 25. March 2004, C.H.S. Watts (SAMA database no. 25-012926)". The beetle was originally labelled as " Copelatus sp.nov." by C.H.S. Watts and has now a red, printed holotype label attached in addition.

European nucleotide archive (genbank) accession number for the 3' end of the mitochondrial cytochrome c oxidase 1 gene: www.ebi.ac.uk/ena/data/view/LN994839

Description.

Size and shape: Beetle small (length of beetle 3.7 mm, greatest width 1.8 mm, length of pronotum 0.6 mm, width of pronotum at base 1.7 mm), comparably parallel-sided (Fig. 1C).

Coloration. Mainly testaceous and slightly translucent with lighter band on elytral base and darker area in middle basal area of pronotum (Fig. 1C).

Surface sculpture. Head (frons), pronotum and elytra striolate; with distinct mircoreticulation and coarser punctation. Metacoxal plates and ventrites 1-4 with few strioles, otherwise with fine mircoreticulation and few punctures. The sixth (apical) ventrite broadly rounded.

Structures. Eyes small in comparison to epigean Exocelina , length of eye c. 0.16 mm, distance between eyes c. 0.86 mm (Figs 1C, 3B). Pronotum with faint lateral bead that does not reach anterior corner. Prosternal process lanceolate, gently rounded ventrally; lateral wings of metaventrite narrow. Flight wings vestigial.

Male. Unknown.

Etymology.

The name is an adjective is the nominative singular derived from the locality name - Holmes Jungle. Latin: saltus = woodland.

Differential diagnosis.

The species is sister to a clade containing Exocelina punctipennis (Lea, 1899) and Exocelina ferruginea (Sharp, 1882) established based on DNA sequence data ( Toussaint et al. 2015), but both these species are larger (> 5mm), and have larger eyes (Figs 1 A–C, 3A, B). Both are epigean species, distributed along the eastcoast of Queensland ( Exocelina punctipennis ) and the Adelaide Hills in South Australia ( Exocelina ferruginea ) (Hendrich et al. in prep.). They are also fully winged.

Habitat.

A small pool in the bed of a small ephemeral creek through eucalypt woodland. A small eyed, wingless Hydraenidae ( Hydraena wattsi Perkins, 2007) was collected at the same time ( Perkins 2007). During the dry season ( June–September) this creek dries out. However, we assume that subsurface water remains in the watercourse during this season providing an interstitial habitat for these flightless, low vagility species.