Unixenus corticolus, Short, Megan & Huynh, Cuong, 2011

Short, Megan & Huynh, Cuong, 2011, The genus Unixenus Jones, 1944 (Diplopoda, Penicillata, Polyxenida) in Australia, ZooKeys 156, pp. 105-122 : 117-120

Unixenus corticolus sp. n. Figs 1D67

Holotype.

Male, Deep Lead Flora and Fauna Park, near Stawell, Vic, 37°00'38"S, 142°44'19"E, 17 June 2005, M. Short and C. Huynh, in Eucalyptus bark, mounted on slide, MV K-11507.

Paratypes.

One male, five females, same data as holotype, mounted on slides, male: MV K-11508, females 1-5: MV K-11509-13; one male and one female from Tidal River, Wilson's Promontory, Vic, 39°01'54"S, 146°18'49"E, 1 November 2005, C. Huynh, in Melaleuca bark, mounted on slides, male: MV K-11514, female: MV K-11515.

Other material examined.

All collected by M. Short and C. Huynh: Ararat Hills Park, Vic, 37°14'30"S, 142°54'30"E, 17 June 2006, in Eucalyptus bark; Flinders, Vic, 38°28'54"S, 145°01'22"E, 25 August 2011, in Melaleuca bark; Pt. Addis, Vic, 38°22'27"S, 144°14'42"E, 21 August 2011, in Eucalyptus bark; Tathra, NSW, 36°43'35"S, 149°59'8"E, 30 December 2007, in Melaleuca bark; Lakes Entrance, Vic, 37°52'45"S, 146°10'49"E, 28 December 2007, in Melaleuca bark; Sunnyside Beach, Mornington, Vic, 38°12'06"S, 145°03'41"E, 17 May 2008, in Melaleuca bark; Launceston, Tas, 41°27'S, 147°09'E, 1 February 2008, in private garden, bark mulch; Holey Plains State Park, Vic, 38°13'S, 146°53'E, 20 April 2008, exuviae, in Eucalyptus bark; Narawntapu National Park, Tas, 42°55'07"S, 147°49'23"E, 31 January 2008, in Eucalyptus bark; Cataract Gorge, Launceston, Tas, 41°27'S, 147°09'E, 1 February 2008, in Eucalyptus bark.

Etymology.

Adjective; this species is almost always found under bark, rarely in litter, in contrast to other species in the genus.

Diagnosis.

4 basiconic sensilla on antennal article VI, basiconic sensillum 4 posterior to coeloconic sensillum, short lateral palps on gnathochilarium (1.5 X diameter of medial palp), 1 seta on femur and no setae on tibia, 5 ornamental trichomes c each side, caudal hooked trichomes with 3-6 hooks. Setae of coxa, prefemur and femur similar to that of Unixenus mjoebergi but with slightly curving and fewer ridges on funicle.

Description.

Length of both sexes 2.4-3.4 mm, caudal bundle 0.45 mm.

Colourdark grey with broad unpigmented band dorsally along midline. Trichomes unpigmented, appearing translucent white in live specimen, long ornamental trichomes c darkly pigmented in contrast to trichomes of caudal bundle that appear white in live specimens.

Head (Fig. 6A) with 8 ocelli each side: 4 dorsal, 4 lateral (1 anterior, 2 medial and 1 posterior). Vertex with 2 posterior groups of trichomes arranged in 2 oblique rows, separated medially by a broad space. Number of trichomes varies, holotype with 10L+10R (anterior rows) and 7L+6R (posterior rows), total each side 17L and 16R. Number of trichomes per side varies 14-18, with no differences between sexes, asymmetrical pattern common with maximum difference 2 trichomes. Trichobothria equal in size, arranged in triangle with angle at b>120o, distance a–b slightly shorter than distance b–c.

Antennae with proportions of 8 articles and 4 sensory cones typical of other species in genus Unixenus (Fig. 6B). Antennal article VI with 4 thick basiconic sensilla of equal length, coeloconic sensillum between basiconic sensilla 3 and 4, setiform sensillum between basiconic sensilla 1 and 2. Antennal segment VII typical of genus with 1 coeloconic sensillum to the posterior followed anteriorly by 2 thick basiconic sensilla of similar height; 1 setiform sensillum between the basiconic sensilla (Figs 6C and 7B). Clypeo-labrum covered in small spherical papillae typical of genus Unixenus , anterior edge with median cleft, no lamella teeth, posterior margin 8-10 setae (Fig. 6E). Gnathochilarium with length lateral palp 1.5 X diameter of medial palp. Lateral palp with 13 cylindrical sensilla, medial palp 21 sensilla (Fig. 6D).

Collum with almost symmetrical arrangement of trichomes, 2 main rows of trichomes each side of medial gap with small number of trichomes between rows, rows linked laterally with small cluster of trichomes (Fig. 6F). Trichomes 24L+23R in holotype, varying between 23-28 per side in paratypes. Small lateral protuberances each with row of 5 forward facing trichomes in holotype, 3-7 in paratypes. In tergites 2-10, trichomes arranged on posterior half of tergite in 2 loose rows with small clusters laterally (Fig. 6F). Trichomes in anterior row directed towards head, those of posterior row directed posteriorly. Trichome number on tergite 2 variable: 26L+26R in holotype, 24-34 each side in paratypes. Conical pleural projections along each side associated with tergites 2-10. Tergal trichomes, all short, barbate and thicker than those of Unixenus mjoebergi and Unixenus karajinensis with three internal longitudinal rows of projections (Figs 6M and 7C), pleural trichomes slightly longer.

Legs 1 and 2 without trochanter, leg 1 also lacks tarsus 1. Trochanter, postfemur, tibia and tarsus 1 lack setae. Chaetotaxy as follows: coxa 1, one seta, coxa 2-3, 2-3 setae, coxa 3-10, 2-4 setae, coxa 13, 0-2 setae (males 2 setae, females 0 setae); prefemur, femur, and tarsus 2 with single seta (Fig. 6G). Structure of setae of coxa, prefemur, femur similar to that of Unixenus mjoebergi and Unixenus karajinensis but with less ridging on funicle and fewer projections, ridging slightly curved around funicle (Figs 6H and 7A); seta of tarsus 2 setiform (Fig. 6I). Telotarsus bearing anterior very thin spinous projection longer than claw. Claw bears anterior and posterior slender processes, large lamella process (Figs 6J and 7D). Males with 2 pairs coxal glands on leg pairs 8-9.

Ornamental trichomes of telson with 4-6 trichomes a, 1b, and 5c (comprising 2 long, 1 medium and 2 shorter dark brown barbate trichomes) each side of midline (Fig. 6K). Caudal bundle trichomes with 3-6 hooks, distal-facing barbs along the stem (Fig. 6L).

Distribution.

Specimens of this species have been found at a number of locations some distance from each other in southern Australia (Fig. 8). Specimens were collected from under bark of Eucalyptus , Melaleuca and Leptospermum . The species was found once only on the ground, in litter formed from mulched bark. Males and females were collected at each location. No specimens were found in museum collections.

Remarks.

Although this species is similar in many ways to Unixenus mjoebergi , it appears to have different habitat requirements as it is rarely found in litter, and then only in bark mulch. This would explain the absence of the species from museum collections that are mainly the result of pitfall trapping or extraction from litter.