Metacoelura articulata ( Schött, 1917 ), Schott, 1917

Ma, Yitong, Zhao, Chun & Greenslade, Penelope, 2016, A new species of Metacoelura (Collembola: Paronellidae) from Australia, and redescription of Metacoelura articulata, Zootaxa 4105 (4), pp. 381-388 : 382-385

Metacoelura articulata ( Schött, 1917)

Figs 1−4 , 10−26

Description. Body length up to 2.0 mm. Colour pattern variable, darker form with most of Ant. I with brown pigment, distal and proximal parts white; proximal part of Ant. II dark blue or brown and distal part white; most of Ant. III and IV white. Eye patches dark blue, two blue stripes between eye patches, one located on the anterior margin of head, the other medially; a pair of stripes present laterally behind eye patches. Th. II, Th. III and Abd. I almost wholly blue or brown except for some pale patches. Abd. II −IV with brownish pigment dorsally and bluish pigment laterally; tibiotarsus and distal part of trochanter with blue pigment; furcula white ( Figs 1, 2 ). In paler form, two longitudinal bluish stripes present on lateral marginal side of Th. II −Abd. II ( Fig. 3 ). Some specimens intermediate in colour between darker and paler patterns ( Fig. 4 ).

Antenna 1.4 times as long as body. Antennal segments of similar length, ratios of segments I:II:III:IV = 1:1.0:1.3:1.2. Distal part of Ant. IV with many sensory setae, normal ciliate setae and apical bulb ( Fig. 10 ). Dorsal cephalic chaetotaxy with 3 antennal (An), 2 median (M) and 7 sutural (S) macrochaetae ( Fig. 11 ). Eyes 8+8, G and H smaller, interocular area with some ciliate setae ( Fig. 12 ). Labral setae 4/5, 5, 4, all slender, prelabral setae ciliate, labral setae smooth; labral papillae not clearly seen ( Fig. 13 ). Maxillary outer lobe with 1 apical seta, 1 subapical seta and 3 hairs on sublobal plate; subapical seta slightly longer than apical one ( Fig. 14 ). Labial setae as M, R, E, L1, L2; all finely ciliate ( Fig. 15 ).

Dorsally Th. II with 20(18)−22 mac in group 1 (G1), 5 in group 2 (G2) and 7−8 in group 3 (G3) ( Fig. 16 ). Th. III with 33 (25)−39 dorsal mac and 12−15 lateral mac. Trochanteral organ with 24−28 smooth, spine-like setae ( Fig. 17 ). Tibiotarsus with inner differentiated ciliate setae, most distal seta on hind leg smooth. Unguis with 4 inner teeth, more proximal e pair located 0.37−0.45 from base of inner edge of unguis, two distal unpaired teeth at 0.67−0.75 and 0.80 −0.85 from base, respectively. Unguiculus lanceolate, and outer edge serrate. Tenent hair thick with clavate tip slightly longer than unguis ( Fig. 18 ).

Abd. IV 7.0−11.0 times as long as Abd. III along dorsal midline. Abd. I dorsally with 17−19 central mac on each side. Abd. II with 6−7 central and 4−5 lateral mac. Abd. III with 2 central and 4 lateral mac ( Fig. 19 ). Abd. IV with 20−25 anterior and 6+6 posterior mac ( Fig. 20 ). Ventral tube anteriorly with 13−18 ciliate setae of different sizes ( Fig. 21 ), posteriorly with about 60 ciliate setae of different sizes, laterally with 3 smooth and 5−7 ciliate setae ( Fig. 22 ). Tenaculum with 4 teeth and 1 large striate seta ( Fig. 23 ). Manubrial plaque with 5 ciliate setae and 2 pseudopores on each side ( Fig. 24 ). Dens without spines, crenulated in medial region ( Fig. 25 ), distal uncrenulated apical portion section of dens 3.0−6.0 times length of mucro ( Fig. 26 ). Mucro small, falcate, lacking basal spine.

Material examined. Eleven females, Australia, Northern Territory, Pungalina/Seven Emu Conservation Area, Calvert River bank, forest pitfall traps, 16o43.282'S, 137 o24.857' E, 14−22. vii. 2012, collected by P. Greenslade. All specimens deposited in South Australian Museum.

Remarks. Our specimens agree well with Schött’s (1917) and Mitra’s (1975, 1993) descriptions of colour pattern. The chaetotaxy of our specimens is almost identical with Mitra’s (1975) descriptions, especially in the chaetotaxy of Abd. I and Abd. II, which is the most useful character for species identification. The difference in the chaetotaxy of lateral areas of Th. III and Abd. II could be because Mitra (1993) did not describe these areas completely or because they are variable ( Table 1 ).

Schött (1917) described the subspecies, M. articulata semicolor , on specimens from the Kimberly Region, northern Western Australia. The only difference between it and the nominate species was colour pattern.

Colour patterns have been shown to be variable in other species, for example Salina anhuiensis Ma, 2012 . There are two colour patterns in our specimens of M. articulata . One is darker with Th. II & III and Abd. I almost wholly blue ( Figs 1, 2 ). This pattern is similar to Schött’s description of M. articulata semicolor . The second pattern is lighter with two longitudinal blue stripes laterally on the body ( Fig 3 ), consistent with Schött’s (1917) and Mitra’s (1973) descriptions of M. articulata articulata . Some of our specimens are intermediate between the darker and paler patterns ( Fig. 4 ). Because our colour-variable specimens were collected from the same locality, Pungalina, and the chaetotaxy is identical for both colour patterns, we hereby synonymise M. articulata semicolor with the nominate species, M. articulata articulata .

Figures

FIGURES 1 − 6. Metacoelura spp. 1 − 4, Metacoelura articulata (Schött, 1917) from Pungalina, Northern Territory. FIGURES 5 − 9, M. majeri sp. nov. from Barrow Island. 5 ‒ 6, habitus; 7, middle part of dens (showing crenulation); 8, distal part of dens; 9, mucro.

FIGURES 10 − 20. Metacoelura articulata (Schött, 1917). 10, apex of Ant. IV; 11, dorsal chaetotaxy of head; 12, eyes and interocular chaetotaxy; 13, labrum; 14, maxillary outer lobe; 15, labium; 16, chaetotaxy of Th. II & III; 17, trochanteral organ; 18, foot complex; 19, chaetotaxy of Abd. I − III; 20, chaetotaxy of Abd. IV.

FIGURES 21 − 26. Metacoelura articulata (Schött, 1917). 21, anterior face of ventral tube; 22, posterior face and lateral flap of ventral tube; 23, tenaculum; 24, manubrial plaque; 25, proximal part of dens (showing crenulation); 26, distal part of dens and mucro.

Tables

TABLE 1. Macrochaetal distribution on known Metacoelura spp.

	M. majeri sp. nov.	M. articulata (Pungalina, NT)1	M. articulata M. varicolor . Holotype ( Mitra, 1975)2
Th. II G 1 G2 29 − 45 7(8)	29 − 45 7(8)	20 (18) − 22 5	10 10 (G1 & G2 4 unknown),
G 3 10–18	10–18	7 (8)	5
Th. III Dorsal area	48−66	33 (25)−39	27 18
Lateral area	17−22	12−15	3?
Abd. I	29−40	17−19	18 9
Abd. II Dorsal area	10−14	6−7	6 2
Lateral area	10−13 (16)	4−5	1 2
Labial setae	M1M2REL1L2 + 1 supplementary seta	MREL1L2	? MEL1L2

1Specimens from Pungalina, 2 Holotype ( Mitra, 1975)