Sensillonychiurus changchunensis, Sun, Xin & Wu, Dong-Hui, 2012

Sun, Xin & Wu, Dong-Hui, 2012, Two new species of tribe Thalassaphorurini Pomorski, 1998 (Collembola: Onychiuridae) from Northeast China, Zootaxa 3226, pp. 61-68 : 62-64

Sensillonychiurus changchunensis sp. nov.

Figs 1–9

Type material. Holotype female, 10 female paratypes. China: Jilin province: Changchun: Gaoxin: 30. IX.2011, litter and soil, Berlese extraction, Song Lihong and Sun Xin leg. All deposited in the Key laboratory of Wetland Ecology and Environment, Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences, Changchun.

Description. Body color white in alcohol. Size 0.45–0.5 mm, holotype: 0.5 mm. Body slender and elongated.

Pseudocellar formulae as 32/133/33343 dorsally, 10/000/00000 ventrally (figs 1, 5 & 8), subcoxa 1 of legs I– III with 1 pso each. Parapseudocelli invisible. Pseudopore formulae as 00/011/11110 dorsally, 00/111/00000 ventrally ( Figs 1, 5 & 8 ).

S-chaetae cylindrical, well differentiated, formulae as 10/011/ 221111 dorsally, 11/000/000110 ventrally ( Figs 1, 5 & 8 ); subcoxae 2 of legs I, II and III with 0, 0 and 1 S-chaeta respectively. Sp absent on head. Microsensilla tiny and blunt, present on Th. II and absent on Th. III ( Fig. 1 ).

Head. Antennae short and distinctly segmented, as long as head or slightly longer. Length ratio of antennal segments I: II: III: IV = 1: 2: 2: 2.2. Ant. IV with two distinct thickened S-chaetae, subapical organite with apex globular and basolateral ms just above posterior chaetae ( Fig. 2 ). Ant. III sensory organ composed of 5 papillae, 3 guard chaetae, 2 small sensory rods, 2 smooth and usually slightly bilobed sensory clubs, and a lateral ms ( Fig. 2 ). Ant. II with 13 chaetae. Ant. I with 8 chaetae. Antennal base without distinct granulation. PAO composed of 7 compound vesicles (fig. 3). Dorsal cephalic chaeta d0 absent ( Fig. 1 ). 4+4 chaetae between posterior inner pso on head. Mandible with strong molar plate and 4 apical teeth. Maxilla bearing 3 teeth and 6 lamellae. Maxillary palp simple with 1 basal chaeta and 2 sublobal hairs (fig. 4). Labral chaetae formula 2/322. Labium with 6 proximal, 4 basomedian (E, F, G and f) and 5 basolateral chaetae (b, c, d, e, e’); labial papillae of AC type, papillae A–E respectively with 1, 4, 0, 3, and 3 guard chaetae ( Fig. 4 ). Postlabial chaetae 3+3 along ventral groove ( Fig. 5 ).

Body chaetotaxy. Ordinary chaetae differentiated in meso- and macrochaetae, ratio sp: m1: p1 on Abd. V = 1: 0.3: 1.2 ( Fig. 1 ). Th. I tergum with 6+6 chaetae. Th. II–III terga with 3+3 chaetae and Abd. I–III terga with 2+2 chaetae on both side of axial line and no axial chaetae. Abd. IV tergum with m0 and p0 axial chaetae, Abd. V with p0 axial chaeta, Abd. VI with only m0 axial chaeta ( Fig. 1 ). Th. I, II and III sterna without chaetae. Abd. III sternum unclearly divided, anterior subsegment without chaetae.

Subcoxa 1 of legs I–III with 3, 4 and 4 chaetae, subcoxa 2 with 1, 4 and 4 chaetae respectively. Tibiotarsi of legs I, II and III with 17 (1, 7, 9), 17 (1, 7, 9) and 16 (1, 6, 9) chaetae ( Figs 6 & 7 ). Unguis without teeth. Unguiculus slender and pointed, 0.5 times as long as inner edge of unguis, with inner basal lamella ( Fig. 6 ). Ventral tube with 6+6 distal chaetae, without anterior or basal chaetae. Furca reduced to a small area of fine granulation situated at contact with border between Abd. III and IV sterna, with 4 small dental chaetae arranged in 2 rows posteriorly; two manubrial rows of chaetae present posteriorly to dental chaetae ( Fig. 8 & 9 ).

Female genital plate with 7–8 chaetae. Anal valves with numerous acuminate chaetae; each lateral valve with a0 and 2a1; upper valves with chaetae a0, 2b1, 2b2, c0, 2c1, 2c2 ( Fig. 8 ). Anal spines absent.

Ecology. In broadleaved litter and soil, in a recreational park in town.

Etymology. Named for the name of the city where we found them.

Remarks. S. changchunensis sp. nov. is probably parthenogenetic because we did not find males within the examined material.

Sensillonychiurus was established by Pomorski and Sveenkova (2006) and was revised by Babenko et al. (2011), nine species reported until now. The new species is very closed to S. amuricus Babenko, Chimitova & Stebaeva, 2011 , but they can be separated from the the number of guard chaetae in AIIIO (3 in changchunensis sp. nov. versus 4 in amuricus ), the position of ms on Ant. IV (low in changchunensis sp. nov. versus upper in amuricus ), the inner basal lamella of unguiculus (distinct in changchunensis sp. nov. versus indistinct in amuricus ), the presence of anal spines (absent in changchunensis sp. nov. versus present in amuricus ) and the length of body (0.45–0.5 in changchunensis sp. nov. versus 0.62–0.72 in amuricus ).

The new species is also similar to S. eisi ( Rusek, 1976) in the group of species without AS, as having the same dorsal pso formula (32/133/33343) and 9 chaetae in the distal whorl of tibiotarsi; but they are different in the dorsal S-chaetae formula (10/011/ 221111 in changchunensis sp. nov. versus 10/011/ 222111 in eisi ), the number of papillae in AIIIO (5 in changchunensis sp. nov. versus 4 in eisi ), the ratio of unguiculus/unguis (0.5 in changchunensis sp. nov. versus 0.3 in eisi ), the number of chaetae on Th. I tergum (6+ 6 in changchunensis sp. nov. versus 5+ 5 in eisi ).

Figures

FIGURES 1 – 7. Sensillonychiurus changchunensis sp. nov.: 1, dorsal chaetotaxy; 2, antenna; 3, PAO and anterior cephalic pso; 4, labium; 5, ventral side of head; 6, distal part of leg III; 7, legIII. Scales: 0.1 mm (1 & 7), 0.01 mm (2 – 6).

FIGURES 8 – 9. Sensillonychiurus changchunensis sp. nov.: 8, ventral side of Abd. II – VI; 9, central part of Abd. IV sternum. Scales: 0.1 mm (8), 0.01 mm (9).