First record of Acrocyrtus Yosii, 1959 (Collemobla, Entomobryidae) from Chinese mainland.

The genus Acrocrytus is reported from Chinese mainland for the first time, with description of two new species Acrocyrtus zhujiensis sp. n. and Acrocyrtus finis sp. n. from Zhejiang Province, East China. They can be separated from other species of this genus by colour pattern, unscaled appendages (antennae, legs and ventral tube), interocular chaetae, labial basal chaetae, bothriotrichal complex chaetae on Abd. II-IV, microchaeta a2 on Abd. II, im on Abd. III and C1p on Abd. IV. Illustrations and a table showing main differences with closest Acrocyrtus species are provided.

Introduction

was established by Yosii 1959 as a subgenus of Bourlet, 1839 for Yosii, 1959 having pointed dental tubercle. Yoshii and Suhardjono (1989) raised it to generic level and established three subgenera (, , ) based on scales distribution of ventral tube. Christiansen and Bellinger (1991) analyzed the phylogenetic relationships among Hawaiian s.l. species and questioned the reliability of dental tubercle. Later, Soto-Adames (2000) made a phylogenetic analysis of Neotropical members of the genus, disagreeing with the previous conclusion and considering that this character has phylogenetic information useful in defining Yoshii’s subgenera; he also suggested that dental tubercle should be used in combination with other characters. Considering the availability of this character in most literature descriptions and how easily it can be observed in practice, we considered that its use at generic level is relevant.

is characterized by the presence of conical pointed dental tubercles, rounded and finely striated scales on body and ventral side of furcula, 8+8 ommatidia (G and H smaller), 4-segmented antennae and apical bulb absent on Ant. IV, bidentate mucro with or without accessory spinelet. It is widely distributed in Southeast Asia, such as Singapore, Malay and Indonesia. So far, more than 26 species of the genus were described all over the world (Pan et al. 2011). Only one species Yosii, 1959 was recorded from Hong Kong (Yosii 1966) and Taiwan (Yoshii 1982), China. Recently, an unidentified species assigned to “cf. ” was also recorded from a cave in Huanjiang (Guangxi) by Deharveng et al. (2008). The two new species of that are studied here represent the first ones described from mainland of China.

Materials and methods

The specimens were cleared in lactic acid, mounted under a coverslip in Marc André II solution, observed using Leica DM2500 and Nikon 80i microscopes. The photographs were taken with Nikon SM1000 microscope using a mounted Nikon DS-Fi1 camera and enhanced with Photoshop CS2. Length data were measured with NIS-Elements Documentation (Nikon). Dorsal cephalic chaetae were designated after Gisin’s system (1967), interocular chaetae after Mari-Mutt (1979, 1986), labial palp chaetae after Fjellberg (1998), labial chaetae after Gisin (1964), dorsal body chaetae after Szeptycki (1979).

Abbreviations.Th. -thoracic segment; Abd. -abdominal segment; Ant. -antennal segment; ms -specialized S-microchaeta(e); S-chaeta(e) -specialized chaeta(e) (including ms); mac -macrochaeta(e); mic -microchaeta(e).

Taxonomy

sp. n.

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http://species-id.net/wiki/Acrocyrtus_zhujiensis

Figs 1 –27 , Table 1

Figures 1–4.

sp. n. 1 colour pattern, lateral view 2 body scale 3 labium and labrum (3A labral intrusion 3B maxillary outer lobe 3C labial basal chaetae R and E) 4 apical manubrium and basal dentes.

Figures 5–17.

sp. n. 5 head cheatotaxy 6 basal Ant. I 7 three kinds S-chaetae on Ant. II 8 Ant. III organ 9 clypeal chaetae 10 cervical chaetae 11 labial base and labial palp 12 cephalic groove 13 coxal macrochaetae (13A fore legs 13B mid legs 13C hind legs) 14 trochanteral organ 15 hind claw 16 anterior side of ventral tube 17 posterior side and lateral flap of ventral tube.

Figures 18–23.

sp. n. 18 distal manubrium and basal dens 19 distal part of ventral manubrium 20 mucro 21–23 dorsal chaetotaxy 21 Th. II 22 Th. III 23. Abd. I.

Figures 24–25.

Dorsal chaetotaxy of sp. n. 24 Abd. II 25 Abd. III (as: antero-lateral S-chaeta).

Figures 26–27.

Dorsal chaetotaxy of sp. n. 26 Abd. IV 27 Abd. V (ps: postero-sublateral S-chaeta).

Table 1.

Main differences between three similar species of .

	Acrocrytus zhujiensis sp. n.	Acrocrytus finis sp. n.	Acrocrytus baii
Dark patches laterally on Abd. II	absent	absent	present
Dark patches postero-laterally on Abd. IV	absent	present	present
Apical bulb of Ant. IV	absent	absent	present
Number of labral papillae	4	4	0
Chaeta M2 on labial base	ciliate	ciliate	smooth
Chaeta R on labial base	slightly ciliate	slightly ciliate	reduced
Chaetae EL1L2 on labial base	ciliate	ciliate	smooth
Inner teeth on unguis	4	4	3
Smooth chaetae on posterior ventral tube	0+0	0+0	1+1
Chaeta a2 on Abd. II	ciliate	smooth	?
Chaetae m3 and m5 on Abd. II	not expanded	expanded	?
Chaeta a2 on Abd. III	not expanded	expanded	?
Chaeta im on Abd. III	ciliate	smooth	?
Chaeta C1p on Abd. IV	ciliate	smooth	?
Distribution	China	China	Vietnam

?: character not provided in original description

Holotype.

♀ on slide, Shaoxin City, Zhuji Country, Dongbaihu, Zhejiang Province, CHINA, 29°34.18'N, 120°24.06'E, 3.X.2009, collection number S4014, collected by Zhi-Xiang Pan & Chen-Chong Si, deposited in Taizhou University.

Paratypes.

6 ♀ and 1 ♂ on slide and 10 in alcohol, same data as holotype. 4 paratypes (2 ♀ on slide and 2 in alcohol) deposited in School of Life Sciences, Nanjing University and others in School of Life Sciences, Taizhou University, China.

Etymology.

Named after the type locality.

Description.

Body length up to 0.93 mm.

Colour pattern. Ground colour pale yellow, with a pair of dark patches present on lateral Abd. III. Violet pigment distributed on antennae and gradually darker towards tip. Eye patches dark (Fig. 1). Scales hyaline, oval to circular (Fig. 2), present on head, body tergites, ventral side of furcula; antennae, ventral tube and legs unscaled.

Head. Ommatidia 8+8, G and H smaller than others. Interocular chaetae as p, r, t, q, s, v; chaeta s smooth, chaetae r and v transformed to scales, chaetae p, t and q ciliate (Fig. 5). Antennae 1.5–2.4 times as long as cephalic diagonal. Antennal segmental ratio as I:II:III:IV = 1:1.3–1.4:1.2–1.9:1.9–3.1. Ant. I with 3 dorsal and 3 ventral basal spiny mic (Fig. 6). Ant. II with 4 basal tiny spiny mic, 1 distal rod-like PageBreakand 12–15 normal S-chaetae (Fig. 7). Ant. III organ with 2 rod-like S-chaetae (Fig. 8). Ant. IV without apical bulb. Anterior part of head with many long, ciliate chaetae but not claviform (Fig. 5). Prelabral and labral chaetae as 4/5, 5, 4, prelabrals ciliate and others smooth, labral intrusion V-shaped, chaetae of c-row thicker than those in other rows; labral margin with 4 conical papillae (Fig. 3). Clypeal chaetae as 3-1-4, without scales between them (Fig. 9). Cervical chaetae as 16 spiny chaetae, lateral two slightly longer than others (Fig. 10). Subapical chaeta of maxillary outer lobe subequal to apical one, 3 smooth sublobal hairs on sublobal plate. Labial palp with 5 papillae PageBreakPageBreakPageBreakas A–E, respectively with 0, 5, 0, 4, 4 guard chaetae; lateral process (l.p.) of labial palp straight, thick and blunt with tip not reaching apex of papilla E. Chaetotaxy of labial base as M, all ciliate, chaeta R shorter than others (Fig. 11). Chaetal row along labial groove with 3 ciliate chaetae, and other postlabial chaetae ciliate (Fig. 12). Mandible with 4+5 (left+right) teeth (Fig. 3).

Leg. Coxae: I, with 7 ciliate mac and 2 pseudopores; II, with 7–8 ciliate mac in the anterior row, 8–11 ciliate mac in the posterior row and 3 pseudopores; III, with 9–11 ciliate mac and 2 pseudopores (Fig. 13). Trochanteral organ with 12–17 smooth spines (1–2 inner) (Fig. 14). Unguis with 4 inner teeth (paired ones at 1/3, middle one at 2/3 and apical one at 3/4 distance from base), 2 lateral teeth (at 1/4 distance from base) and 1 outer tooth (at 1/5 distance from base). Unguiculus slender and truncate with outer edge serrate. Tenent hair clavate, subequal to inner edge of unguis in length, and slightly longer than unguiculus. A distal smooth chaeta on tibiotarsus III subequal to unguiculus in length (Fig. 15).

Ventral tube. Anterior face with 14+14 ciliate chaetae; posterior face without smooth chaeta (Fig. 16); lateral flap with 6–8 smooth and 2–4 ciliate chaetae (Fig. 17).

PageBreakFurcula. Manubrial plaque with 2–3 inner, 4–6 outer ciliate chaetae and 2 pseudopores. Dental tubercles conically pointed (Figs 4, 18). Ventral terminal manubrium with 2+2 ciliate chaetae (Fig. 19). Distal smooth part of dentes 2.1–2.5 times as long as mucro. Mucro bidentate, mucronal basal spine reaching subapical tooth with an accessory spinelet (Fig. 20).

PageBreakChaetotaxy. Dorsal cephalic mac as R; R1s absent. Body mac as 00/0100+3, S-chaetae as 21/11253, ms as 10/10100. Th. II slightly protruded over head, with 1–2 rows of ciliate “collar” mac, 2 antero-lateral S-chaetae (ms external to another S-chaeta), 6 (p1–6) smooth mic and 5 anterior unclear homology smooth mic (Fig. 21). Th. III with 1 S-chaeta external to m7; 15 (a1–4, a6, m2, m4–6 and p1–6) smooth mic, 3 (a7, m7 and m7e) ciliate mac and a lateral unclear homology ciliate chaeta (Fig. 22). Abd. I with 1 ms, 12 (a1–3, a5–6, m2–6 and p5–6) smooth mic and 2 lateral unclear homology ciliate chaetae (Fig. 23). Abd. II with 1 central S-chaeta (as), 1 (a2) ciliate mic, 13 (a3, a6–7, m3e, m4, m6–7, p4–7, p5p and el) smooth mic, 1 ciliate and slightly modified mic (mi), 2 (Lm and Li) ciliate, modified and fan-shaped mic, 2 (m3 and m5) ciliate mac; chaetae a2p and ml absent (Fig. 24). Abd. III with 1 central S-chaeta (as) and 1 lateral ms, 5 (mi, ml, a2, im, em and am6; ml sometimes present on one side) ciliate and slightly modified mic, 4 (Li, Lm, Ll and a6) strongly modified and fan-shaped mic, 8 (a3, a7, m3, m7, p3–5 and p7) smooth and subequal mic, 3 (pm6, m7a and p6) ciliate mac (Fig. 25). Abd. IV with 1 anterior (as) and 1 posterior (ps) short S-chaetae and 3 median elongate S-chaetae, 22 (A2–6, B2–3, Be2, C1–4, T1, T3, T5–6, Te3, D2–3, D1p, E1 and Fe1) smooth mic, 2 (C1p and T7) ciliate mic, 6 (m, a, s, D1, pi and pe) ciliate, strongly modified and fan-shaped mic, 13 (B4–6, De1, De3, D3p, E2–4, F2–3, F3p2, Fe4 and Fe6) ciliate mac, 4(E4p, E4p2, F2p and F3p2) mic (Fig. 26). Abd. V with 3 S-chaetae (Fig. 27).

Ecology.

In the leaf litter of , along a lake.

Remarks.

This new species is characterized by colour pattern, clavate tenent hair, unscaled appendages (antennae, legs and ventral tube), 4 conical labral papillae, ventral tube with ciliate chaetae present on lateral flap and without smooth chaeta on posterior side, and ciliate mic a2 on Abd. II.

It is similar to Vietnamese Nguyen, 2005 in clavate tenent hair, claw, unscaled appendages (antennae and ventral tube). However, it can be easily distinguished from it by pigment absent on Th. II–III and Abd. II (versus present), ciliate labial chaetae EL (versus smooth), M subequal to M on labial base (versus M smaller than M), absence of smooth chaetae on posterior face of ventral tube (versus 1+1 smooth chaetae) and unscaled legs (versus scaled).

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Figs 28 –37 , Table 1

Figures 28–30.

sp. n. 28 colour pattern, lateral view 29 body scale 30 labium and labrum (30A labral intrusion 30B labial papillae D, E and l.p. 30C labial base).

Figures 31–33.

Dorsal chaetotaxyof sp. n. 31 Th. II 32 Th. III 33 Abd. I.

Figures 34–35.

Dorsal chaetotaxyof sp. n. 34 Abd. II 35 Abd. III.

Figures 36–37.

Dorsal chaetotaxyof sp. n. 36 Abd. IV 37 Abd. V.

1 ♀ on slide, Taizhou City, Dalei Mountain, Zhejiang Province, CHINA, 29°02.25'N, 120°53.03'E, 25.X.2009, collection number S4023, collected by Zhi-Xiang Pan, deposited in Taizhou University.

11 ♀ on slide and 15 in alcohol, same data as holotype. 4 paratypes (2 ♀ on slide and 2 in alcohol) deposited in School of Life Sciences, Nanjing University and others in School of Life Sciences, Taizhou University, China.

Named after the type locality, which is the border (latin word “finis”) of the three adjacent cities.

Body length up to 1.2 mm.

Colour pattern. Ground colour from yellow to slightly brown, a pair of dark lateral patches of Abd. III and a pair of dark postero-lateral patches of Abd. IV, slightly violet pigment distributed on antennae and gradually darker towards tip, eye patches dark (Fig. 28). Scales hyaline, oval to circular (Fig. 29), present on head, body tergites and ventral side of furcula, and absent on antennae, legs and ventral tube.

Head. Ommatidia 8+8, G and H smaller than others, interocular chaetae as p, r, t, q, s, v; chaeta s smooth, chaetae p, t, q ciliate, chaetae r and v transformed to scales. Antennae 1.4–2.0 times as long as cephalic diagonal. Antennal segmental ratio as I:II:III:IV = 1:1.3–1.9:1.5–2.5:2.5–5.0. Ant. I with 3 dorsal and 3 ventral basal PageBreakspiny chaetae. Ant. II with 4 basal tiny spines, 11–14 short and 1 distal rod-like S-chaetae. Ant. III organ with 2 rod-like S-chaetae. Ant. IV without apical bulb. Anterior part of head with many ciliate and long, but not claviform chaetae. Cervical with 16 PageBreakspiny chaetae, all subequal in length. Prelabral and labral chaetae as 4/5, 5, 4, prelabrals ciliate and others smooth, chaetae of c-row thicker than other row chaetae; labral intrusion V-shape; labral margin with 4 papillae. Clypeus without scales. Subapical chaeta of the maxillary outer lobe subequal to apical chaeta, 3 smooth sublobal hairs on sublobular plate. Labial palp with five papillae as A–E, respectively with 0, 5, 0, 4, 4 guard chaetae; lateral process of labial palp straight, thick with tip not reaching apex of papilla E. Chaetotaxy of labial base as M, all ciliate, chaeta r shorter than others. Chaetal row along labial groove with 3 ciliate chaetae, and other postlabial chaetae ciliate. Mandible with 4+5 (left+right) teeth (Fig. 30).

Leg. Coxae: I, with 5–7 ciliate mac and 2 pseudopores; II, with 6–7 ciliate mac in the anterior row, 7–9 ciliate mac in the posterior row and 3 pseudopores; III, with 6–7+3 ciliate mac and 2 pseudopores. Trochanteral organ with 10–14 smooth spiny chaetae. Unguis with 1 outer (at 1/5 distance from base), 2 lateral (at 1/4 distance from PageBreakPageBreakbase) and 4 inner teeth (paired ones at 1/3, middle one at 2/3 and apical one at 3/4 distance from base to apical inner unguis), all tiny. Unguiculus slender and truncate with outer edge slightly serrate. Tenent hair clavate, subequal to inner margin of unguis, and slightly longer than unguiculus. Supraempodial chaeta subequal to unguiculus.

Ventral tube. Anterior face with 9–15 larger ciliate chaetae; posterior face without smooth chaetae; lateral flap with 6–7 smooth and 2–3 ciliate chaetae.

Furcula. Manubrial plaque with 2–3 inner, 4–6 outer ciliate chaetae and 2 pseudopores, ventral manubrium with 2+2 ciliate terminal chaetae. Dental tubercles conically pointed. Distal smooth part of dentes 1.5–2.0 times as long as mucro. Mucro bidentate, mucronal basal spine reaching subapical tooth with two accessory spinelets.

Chaetotaxy. Dorsal cephalic mac as R, P sometime absent. Body mac as 00/0100+3, S-chaetae as 21/11253, ms as 10/10100. Th. II slightly protruded over head, with 2 antero-lateral S-chaetae (ms postero-external to another one), 6 (p1–6) smooth and subequal mic and 5 anterior smooth mic of unclear homology (Fig. 31). Th. III with 1 S-chaetae external to m7, 15 (a1–4, a6, m2, m4–6 and p1–6) smooth mic, 3 (a7, m7 and m7e) mac and one other mac of unclear homology (Fig. 32). Abd. I with 1 ms external to a6, 12 (a1–3, a5–6, m2–6 and p5–6) smooth mic and 2 lateral ciliate mac of unclear homology (Fig. 33). Abd. II with 1 central S-chaetae (as), 1 (mi) ciliate and blunt mic, 14 (a2–3, a6–7, m3e, m4, m6–7, p4–5, p5p, p6–7 and el) smooth and subequal mic, 2 (Lm and Li) ciliate and slightly expanded mic, 2 (m3 and m5) ciliate mac with tip expanded, chaetae a2p and ml absent (Fig. 34). Abd. III with 1 central S-chaeta (as) and 1 lateral ms, 5 (a2, mi, ml, em and am6) ciliate mic with tip expanded, 4 (Li, Lm, Ll and a6) ciliate modified and fan-shaped mic, 9 (im, a3, a7, m3, m7, p3–5 and p7) smooth mic, 3 (pm6, m7a and p6) ciliate mac (Fig. 35). Abd. IV with 1 anterior (as) and 1 posterior (ps) short S-chaetae and 3 elongate median S-chaetae, 22 (A2–6, B2, B3, Be2, C1–4, C1p, T1, T3, T5–6, D1p, D2–3 and Fe1) smooth mic, 15 (B4–6, T7, D3p, De1, De3, E1–4, F1–3, Fe4 and Fe6) ciliate and mac, 5 (Te3, E4p, E4p2, F3p and F3p2) as mic, 4 (m, a, s and D1) ciliate and strongly fan-shaped mic, 2 (pi and pe) ciliate mic with tip expanded (Fig. 36). Abd. V with 3 S-chaetae (Fig. 37). Abd. IV:Abd. III = 2.6–4.1:1.

In leaf litter of , and , in bryophyta and on farmland.

The new species is easily distinguished from other by 4 abdominal lateral patches, morphology of interocular chaetae v, r and s, cephalic mac as R, 4 papillae and thicken c-row chaetae on labrum, smooth mic a2, im and C1p on Abd. II, Abd. III and Abd. IV, respectively, unscaled appendages (antennae, ventral tube and legs).

The species is most similar to sp. n. in cephalic chaetotaxy, labral papillae, claw, furcula, macrochaetotaxy and S-chaetotaxy. However, the two species are different in colour pattern, morphology of chaetae a2, m3 and m5 on Abd. II, a2 and im on Abd. III, C1p on Abd. IV. Main differences between two new species are listed in Table 1.

Discussion

Dental tubercles are pointed in and rounded in . However, it is sometimes uneasy to recognize the shape of dental tubercles. Their shape maybe wrongly observed in different visual angles, pointed in lateral view but “rounded” in facial view. They need to be observed under various angles. Another interesting point is that some species of Yoshii (1982, 1989) with colour patterns similar to our species (pigment on Abd. III) were assigned to rather than . Our new species would be placed in due to habitus compared with those Southeast Asia taxa (Deharveng, personal communication). Actually, more Chinese species with similar patterns in our collection have pointed and relatively long dental tubercles. Since the works of Yosii, no significant advance has been made for the classification of s. l. Molecular tools are expected to help discriminate Lepidocyrtinae genera in the future.