Allonychiurus megasomus, Sun, Xin, Yan, Haijuan & Chen, Jian-Xiu, 2009

Sun, Xin, Yan, Haijuan & Chen, Jian-Xiu, 2009, A new species of the genus Allonychiurus from China (Collembola: Onychiuridae), Zootaxa 2194, pp. 61-68 : 62-66

Allonychiurus megasomus sp. nov.

( Figures 1–17 , Tables 1–2)

Type material. Holotype: female, China: Jiangsu Province: Nanjing: Qingliangshan Park, 11.iv.2006, collection number C9459, collected by XIE Guilin and JIANG Jigang. Paratypes: 9 females and 1 juvenile male, same data as holotype. Deposited in School of Life Science, Nanjing University, China; 2 Paratypes in the Museum National d’Histoire Naturelle, Paris, France.

Abd. V present absent present present present present seta m0 (after fig. 62,

Rusek 1971)

Ventral tube 8+8 6+6 6+6 8+8?? setae

Description. Body length: Up to 2.1 mm, holotype 1.46 mm.

Body colour: Milky white in alcohol.

Pseudocelli (pso): formula as 32/133/33343 dorsally ( Figs. 1 & 2 ), 11/000/01110 ventrally, and 1/1/1 on subcoxae ( Fig. 1 ).

Parapseudocelli (psx): 1+1, only found on sternum of Abd. I, near base of ventral tube ( Fig. 13 ).

Sensilla (s): thick and blunt, formula as 2/012/22222 dorsally ( Figs. 1 & 2 ) and 2/000/00000 ventrally ( Fig. 11 ).

Microsensilla (ms): tiny, thick and blunt, formula as 0/011/00000 dorsally ( Fig. 1 ).

Head: Antennae short and distinctly segmented, 0.6–0.7 times as long as head. Antennal base distinctly marked with granulation. Ratio of length of antennal segments I:II:III:IV=1.0:1.6–2.0:1.5–1.9:3.3–3.7. Ant. III sensory organ composed of 5 papillae, 5 guard setae, 2 small rods and 2 clubs; clubs mulberry-shaped. Lateral ms just behind sensory organ. Ant. IV subapical organite with distal part expanded to a globular shape, basolateral ms situated in posterior row of setae ( Figs. 3–6 ). Anterior cephalic dorsal pso located in finely granulated area near antennal base. PAO composed of 18–22 secondarily granulated vesicles arranged in 2 rows along axis of organ ( Fig. 7 ). Dorsal seta d0 present. 4+4 setae between two posterior inner pso, p1 slightly anterior to others ( Fig. 1 ). Labral setae 4/3, 4, 2 ( Fig. 8 ). Labium AC type ( Fjellberg 1999), papillae A, B, C, D, E respectively with 1, 4, 0, 3 and 4 guard setae ( Fig. 9 ). Labial proximal setae 6, basomedian setae 4 (E, F, G, and f), basolateral setae 5 (b, c, d, e, e’) (D’Haese 2003) ( Fig. 10 ). Postlabial setae 3+3 along ventral groove ( Fig. 11 ).

Body chaetotaxy: Body setae smooth, of different lengths and usually arranged symmetrically. Th. I–Abd. III dorsally without median setae. Th. I with 7–8+7–8 dorsal setae. Th. II–III and Abd. I–III respectively with 4+4 and 3+3 dorsal setae along median line. Abd. IV with dorsal median setae m0 and p0, Abd. V with m0, Abd. VI with a0 and p0 ( Figs. 1 & 2 ). Th. I–III with 0+0, 1+1, 1+1 (2+2) ventral setae respectively between coxae. Subcoxa 1 with 4, 5, 5, subcoxa 2 with 1, 4, 4 setae respectively on legs I–III.

Appendages: Tibiotarsal setae as 21(11, 8, 2), 20(11, 7, 2) and 19(11, 7, 1) respectively on legs I–III; Unguis without teeth. Unguiculus very slender and pointed, without inner basal lamella, 0.6–0.7 as long as inner edge of unguis ( Fig. 12 ). Ventral tube with 8+8 distal setae and no basal setae ( Fig. 13 ). Furcula reduced to a finely granulated area, with 4 small setae in two rows present posterior furcal rudiment ( Fig. 14 ).

Genital plate consisting of 13 setae in male (preadult) and 17–21 in female ( Figs. 15 & 16 ). Male ventral organ absent. Anal valves with numerous acuminate setae; each lateral valve with a0 and 2a1 setae; upper valve with a0, b0, 2b1, 2b2, c0, 2c1 and 2c2 (after Yoshii 1996) ( Fig. 18 ). Anal spines stout, set on distinct papillae, about 0.8 times length of inner edge of hind unguis ( Figs. 2 & 17 ).

Ecology. Found under moist leaf and grass litter, stones and bricks in woods of deciduous trees and bamboo.

Etymology. The name of the new species is derived from Greek megas and soma. It refers to the large size of the species.

Remarks. The new species is diagnosed by the arrangement and number of pseudocelli, ventral parapseudocelli, dorsal sensilla, the form of the PAO, the chaetotaxy of Abd. IV and V, the number of setae on the tibiotarsus, the unguiculus without basal lamella and the number of setae on the ventral tube.

It is similar to some Asian species, such as: shanghaiensis ( Rusek, 1971), kimi ( Lee, 1973), shinbugensis ( Lee, 1974), jongaksanensis ( Weiner, 1989), flavescens ( Kinoshita, 1916) in the Ant. III sensory organ, dorsal sensilla, abdominal dorsal pso, median setae on Abd. V and VI. However, it is easily separated from them by the characters listed in the Table 1.

Figures

FIGURES 1 – 6. Allonychiurus megasomus sp. nov. 1, Dorsal cephalic and thoracic chaetotaxy. 2, Dorsal abdominal chaetotaxy. 3, Right antenna. 4, Ant III sensory organ and ms, dorsal view. 5, Club of Ant III sensory organ. 6, Ant. IV subapical organite.

FIGURES 7 – 13. 7, PAO and anterior cephalic pso. 8, Labrum. 9, Labial palp. 10, Labium. 11, Ventral side of head, showing chaetotaxy, sensilla, and pseudocelli. 12, Hind tibiotarsus, lateral view. 13, Ventral tube, lateral view.

FIGURES 14 – 18. 14, Remnant of furca. 15, Male (preadult) genital plate. 16, Female genital plate. 17, Anal spine. 18, Anal valves.