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Research Article
Two new species of Sinella from Guangdong Province, China (Collembola: Entomobryidae)
expand article infoGuo-Liang Xu, Wei-Yu Chen§
‡ Guangzhou University, Guangzhou, China
§ Nanjing Plant Protection Station, Nanjing, China
Open Access

Abstract

Two new blind species of Sinella are described from Guangdong Province, China. Sinella colubra sp. n. possesses minute smooth postlabial chaetae, long mucronal spine, and 4+4(5) lateral mac on Abd. IV, and can be distinguished from two closely related species by the postlabial chaetae and the dorsal macrochaetotaxy. Sinella zhangi sp. n. is also described and can be diagnosed by having minute labial chaeta r and postlabial chaetae X and X4, 5+5 mac on Abd. I, 4+4 central mac on Abd. II, and 4+4 central and 5+5 lateral mac on Abd. IV.

Keywords

Blind species, chaetotaxy, springtail, Sinella colubra sp. n., Sinella zhangi sp. n., South China

Introduction

The genus Sinella Brook, 1882 is distributed worldwide and is very abundant in China. Deharveng (1990), Chen and Christiansen (1993) and Zhang et al. (2009, 2011) made significant contributions to the modern taxonomy of the genus. Members of the genus have 4-segmented antennae, reduced eye number (0‒6 on each side), pigment reduced or absent, polymacrochaetotic chaetotaxy, bidentate mucro, and no dental spines and scales. So far, 39 species, including 14 blind ones, have been recorded from China. Among them, only two eyed species have been recorded from Guangdong Province: Sinella curviseta Brook, 1882 and Sinella longisensilla Zhang, 2013. In this study, two new blind species are described from Guangdong.

Materials and methods

Specimens were cleared in Nesbitt’s fluid (Krantz 1978), mounted under a coverslip in Hoyer’s solution, and observed using a Nikon E80i microscope. The labial chaetae terminology follows Gisin’s system (1967). The dorsal and ventral chaetotaxy of head are described after Chen and Christiansen (1993), completed for the anterior part of head after Jordana and Baquero (2005) and Soto-Adames (2008). Dorsal body chaetae are designated following Szeptycki (1979) and Zhang et al. (2011). The number of macrochaetae is given by half-tergite in the descriptions (left side of tergites drawn in figures). Tergal S-chaetotaxic formula follows Zhang and Deharveng (2015). All descriptions are based on fully developed adults if not otherwise mentioned. Symbols representing chaetal elements used in the figures are as follows: large circle, macrochaeta; small circle, mesochaeta; cross, bothriotrichum; circle with a slash, pseudopore; dotted circle, chaetae present or absent. All materials are deposited in the collections of the Department of Entomology, College of Plant Protection, Nanjing Agricultural University (NJAU), P. R. China.

Abbreviations

Th. thoracic segment

Abd. abdominal segment

Ant. antennal segment

mac macrochaeta/ae

mic microchaeta/ae

mes mesochaeta/ae

ms S-microchaeta/ae

sens ordinary tergal S-chaeta/ae

Taxonomy

Sinella colubra sp. n.

Figs 1–12, 13–16, Table 1

Type material

Holotype: ♂ on slide, China, Guangdong Province, Huizhou City, Longmen County, Nankunshan Natural Reserve, 23°38'4.01”N, 113°51'15.25”E, altitude 497 m, 24 August 2010, Z-X Pan and Y-T Ma leg. (# S4143). Paratypes: ♂ and 3 ♀♀ on slides and 3 in alcohol, same data as holotype.

Other material

♀ on slide, China, Guangdong Province, Nanling National Natural Reserve, 24°55'42.6"N, 113°0'58.3"E, altitude 1026 m, 22 July 2010, F Zhang and Z-H Li leg. (# C9640).

Diagnosis

No eyes. Long smooth straight chaetae present on antennae. Clypeal chaetae eight and median three much smaller. Labial chaetae as mrel1l2. Postlabial chaetae X and X2‒4 minute. “Smooth” inner differentiated tibiotarsal chaetae present. Manubrium without smooth chaetae. Mucronal spine long, with tip nearly reaching apical tooth. Abd. I with 6+6 mac. Abd. II with 3+3 central mac. Abd. IV with 7+7 central and 4+4 lateral mac.

Table 1.

Comparison among S. colubra sp. n., S. insolens and S. sineocula. Rare character states are noted and placed in parentheses.

Characters S. colubra sp. n. S. insolens S. sineocula
Mac in Gr. II on dorsal head 3(4) usually 4‒5(6‒8) usually 5‒6(4)
Labial chaeta M1s absent present absent
Postlabial chaetae X and X2‒4 smooth, minute cliate, large ciliate, large
Mac m5i on Th. III absent present absent
Mac on Abd. I 6+6 7(6)+7(6) 7(6)+7(6)
Central mac on Abd. II 3+3 4+4 3+3
Lateral mac on Abd. IV 4(5)+4(5) 6+6 6+6

Description

Body length up to 1.50 mm. Body pale in alcohol.

Antenna 1.63‒1.93 times as long as cephalic diagonal. Antennal segments ratio as I : II : III : IV = 1 : 1.77‒2.00 : 1.64‒1.74 : 2.57‒2.91. Smooth spiny mic at base of antennae: three dorsal, three ventral on Ant. I; one internal, one external and two ventral on Ant. II. Ant. II distally with one (rarely two) rod-like sens. Ant. III organ with two slightly expanded internal sens. Ant. IV with a knobbed subapical organ. Ant. II. with 2‒4 ventral long smooth straight chaetae.

Eyes absent in all specimens. Prelabral and labral chaetae 4/ 5, 5, 4, all smooth; labral intrusion U-shaped (Fig. 1). Clypeal chaetae eight in number, including three small median chaetae (Fig. 2). Dorsal cephalic chaetotaxy with four antennal (An), three median (M) and eight sutural (S) mac; Gr. II with 3(4) mac (Fig. 3). Mandibles with 4/5 (left/right) teeth. Subapical chaeta of maxillary outer lobe slightly thicker than apical one; three smooth sublobal hairs on maxillary outer lobe. Lateral process of labial palp slightly thicker than normal chaetae, with tip extending beyond apex of labial papilla (Fig. 4). Labial chaetae as mrel1l2, all smooth, r/m=0.67‒0.79; chaetae X and X2‒4 minute; chaeta X3 rarely absent; H1-4 smooth. Cephalic groove with 9(8) chaetae, four of them smooth and others ciliate (Fig. 5).

Figures 1–12. 

Sinella colubra sp. n. 1 labrum 2 clypeal chaetae 3 dorsal cephalic chaetotaxy 4 lateral process and labial papilla E 5 chaetae on the ventral side of head 6 trochanteral organ 7 hind claw 8 anterior face of ventral tube 9 ventral face and lateral flap of ventral tube 10 distal part of anterior face of manubrium 11 manubrial plaque 12 mucro.

Trochanteral organ with 17‒19 smooth spiny chaetae; 11–12 in arms and 5‒7 internal (Fig. 6). Partial inner differentiated tibiotarsal chaetae “smooth” with ciliations closely appressed to axis (Chen and Christiansen 1993). Tibiotarsi distally with ten chaetae in a whorl. Unguis with three inner, one outer, and two lateral teeth; two paired teeth unequal, outer one large. Unguiculus with a large outer tooth. Tenent hairs of all legs pointed but clavate in one male specimen (Fig. 7). Abd. IV 3.72‒4.60 times as long as Abd. III along dorsal midline. Ventral tube anteriorly with 6‒7 ciliate chaetae on each side, two of them much larger than others (Fig. 8); posteriorly with about 13 chaetae, most of them small and weakly ciliate; each lateral flap with two ciliate and six smooth chaetae (Fig. 9). Male genital plate not clearly seen. Manubrium dorsally without smooth chaetae; ventrally with 5+5 distal ciliate chaetae (Fig. 10). Manubrial plaque with 2+2(1) pseudopores and 3+3 ciliate chaetae (Fig. 11). Distal smooth part of dens 1.08–1.57 as long as mucro. Mucro bidentate with apical tooth larger; basal spine long, with tip nearly reaching apical tooth (Fig. 12).

Th. II with three medio-medial mac (m1, m2, m2i), three medio-lateral mac (m4, m4i, m4p), 14‒18 posterior mac, one ms and two sens; ms interior to sens al. Th. III with 29‒32 mac and two lateral sens; a6i, p5, p6, m6, m6i, m6p, m6e and m6ai2 present as mac; mac m5i absent (Fig. 13). Abd. I with six mac (a3, m2–4, m2i, m4p), one ms and one sens; sens interior to ms. Abd. II with three central mac (m3, m3e, m3ep), one lateral mac (m5) and two sens. Abd. III with one central mac (m3), three lateral mac (am6, pm6, p6) and two sens; ms absent (Fig. 14). Abd. IV with seven central mac (I, M, A5–6, B4–6), four (rarely five) lateral mac (D3, E2–4), and at least 17 sens (Fig. 15). Abd.V with three sens (Fig. 16).

Figures 13–16. 

Tergal chaetotaxy of Sinella colubra sp. n. 13 thorax 14Abd. I‒III 15Abd. IV 16Abd. V.

Etymology

Named after the snake Bungarus multicinctus Blyth found in the sampling site.

Ecology

In soil of bamboo forest, near termitarium.

Remarks

Sinella colubra sp. n. is most similar to Sinella insolens Chen & Christiansen, 1993 and Sinella sineocula Chen & Christiansen, 1993 in morphology of unguis and unguiculus, long mucronal spine, absence of smooth chaetae on manubrium, medial and posterior mac on Th. II, 1+1 central and 3+3 lateral mac on Abd. III, and 7+7 central mac on Abd. IV. It differs from them in 3+3(4) cephalic mac on Gr. II, absence of labial chaeta M1s, minute postlabial chaetae X and X2‒4, absence of mac m5i on Th. III, 6+6 (a2 as mes) mac on Abd. I, absence of mac m3ei on Abd. II, and 4+4(5) lateral mac on Abd. IV.

Sinella zhangi sp. n.

Figs 17–25, 26–27

Type material

Holotype: ♂ on slide, China, Guangdong Province, He Mountain, in soil of secondary eucalypt forest, 22 October 2012, Guoliang Xu leg. (# Xu-2012). Paratypes: 1 ♀ on slide and 1 juvenile in alcohol, same data as holotype.

Diagnosis

No eyes. Long smooth straight chaetae absent on antennae. Labial chaeta r and postlabial chaetae X and X4 minute. “Smooth” inner differentiated tibiotarsal chaetae present. Tenent hairs clavate. Manubrium without smooth chaetae. Mucronal spine short, with tip reaching subapical tooth. Chaeta p5 as mac on Th. II. Abd. I with 5+5 mac. Abd. II with 4+4 central mac. Abd. IV with 4+4 central and 5+5 lateral mac.

Description

Body length up to 1.32 mm. Body pale in alcohol.

Antenna 2.04 times as long as cephalic diagonal. Antennal segments ratio as I : II : III : IV = 1 : 1.71 : 1.86: 2.71. Smooth spiny mic at base of antennae three dorsal, three ventral on Ant. I: one internal, one external and one ventral on Ant. II. Ant. II distally with one rod-like S-chaeta. Two internal sens of Ant. III organ rod-like. Long smooth straight chaetae absent on antennae.

Eyes absent in all specimens. Prelabral and labral chaetae 4/ 5, 5, 4, all smooth; three chaetae of first row longer than lateral chaetae. Clypeal chaetae not clearly seen. Dorsal cephalic chaetotaxy with four antennal, three median (M) and eight sutural (S) mac; Gr. II with four mac (Fig. 17). Mandibles with 4/5 (left/right) teeth. Subapical chaeta of maxillary outer lobe subequal to apical chaeta; three smooth sublobal hairs on maxillary outer lobe. Lateral process of labial palp thicker than normal chaetae, with tip extending beyond apex of labial papilla (Fig. 18). Labial chaetae as mrel1l2, all smooth, r/m=0.20; chaetae X and X4 smooth, minute; chaetae X2‒3 absent; H1, H2 and H4 ciliate. Cephalic groove with eight chaetae, two smooth and others ciliate (Fig. 19).

Figures 17–25. 

Sinella zhangi sp. n. 17 dorsal cephalic chaetotaxy 18 lateral process and labial papilla E 19 chaetae on the ventral side of head 20 hind claw 21 lateral flap of ventral tube 22 manubrial plaque 23 mucro 24 thoracic chaetotaxy 25 chaetotaxy of Abd. I‒III.

Trochanteral organ with nine smooth spiny chaetae; five in arms and four internal. Some inner differentiated tibiotarsal chaetae “smooth” with ciliations closely appressed to axis. Tibiotarsi distally with ten chaetae in a whorl. Unguis with three inner teeth; two paired teeth unequal, outer one larger. Unguiculus with a large outer tooth. Tenent hairs clavate (Fig. 20). Abd. IV 3.42 times as long as Abd. III along dorsal midline. Ventral tube anteriorly with seven ciliate chaetae; two of them much larger than others; posteriorly not clearly seen; each lateral flap with seven smooth and one ciliate chaetae (Fig. 21). Manubrium without smooth chaetae. Manubrial plaque with 2+2 pseudopores and 3+3 ciliate chaetae (Fig. 22). Distal smooth part of dens 1.72 times as long as mucro. Mucro bidentate with apical tooth longer than subapical tooth; basal spine short, reaching tip of subapical tooth (Fig. 23).

Th. II with three medio-medial mac (m1, m2, m2i), three medio-lateral mac (m4, m4i, m4p), 19 posterior mac, one ms and two sens; ms interior to sens al. Th. III with 30 mac and two lateral sens (Fig. 24). Abd. I with five mac (m2–4, m2i, m4p), one ms and one sens; sens interior to ms. Abd. II with four central mac (a2, m3, m3e, m3ep), one lateral mac (m5) and two sens. Abd. III with one central mac (m3), three lateral mac (am6, pm6, p6) and two sens; ms absent (Fig. 25). Abd. IV with four central mac (I, M, B5, A6), five lateral mac (E2–4, E2p, F1), and at least 11 sens; as and ps shorter than others (Fig. 26). Abd.V with three sens; chaetae m2, m3, m5, a6, p1, p3–5 and ap6 present as mac (Fig. 27).

Figures 26–27. 

Tergal chaetotaxy of Sinella zhangi sp. n. 26Abd. IV 27Abd. V.

Etymology

Named after the Chinese collembologist Dr. Feng ZHANG, who has made great contributions to the taxonomy of Sinella.

Ecology

In decomposing leaves along the roads.

Remarks

Sinella zhangi sp. n. is most similar to Sinella quadriseta Zhang, Bedos & Deharveng, 2014 in absence of eyes, tip of lateral process of labial palp beyond apex of labial papilla, morphology of unguis and unguiculus, and mucronal spine, but differs from it in smooth, minute labial and postlabial chaetae r, X and X4, clavate tenent hairs, “smooth” inner differentiated tibiotarsal chaetae, 4+4 mac in Gr. II on dorsal head, absence of mac m2, m2i, m4i and m4p on Th. II, 5+5 mac on Abd. I (m4p present), and 4+4 central mac on Abd. II (m3ep present). It is also similar to Chinese species Sinella affluens Chen & Christiansen, 1993 in 4+4 mac on dorsal head, “smooth” inner differentiated tibiotarsal chaetae, clavate tenent hairs, number of teeth on unguis and unguiculus, minute postlabial chaetae X and X4, 2+2 pseudopores and 3+3 ciliate chaetae on manubrial plaque, medial mac on Th. II, 1+1 central mac on Abd. III, and 4+4 central mac on Abd. IV, but differs from the latter in absence of eyes, short mucronal spine, minute labial chaeta r, p5 present as mac on Th. II, m5i present as mac on Th. III, 5+5 mac on Abd. I (a3) as mes, 4+4 central mac on Abd. II (a2 as mac), 5+5 lateral mac on Abd. IV (F1 as mac).

Acknowledgments

Thanks are given to Dr. Feng Zhang (NJAU), who provided the material and facilities when we visited his lab in August, 2015.Thanks should be given to Mr. Morgan A. McClure, who helped to check the English text. The present study was supported by the National Natural Sciences Foundation of China (41571247) and High Level University Construction Project of Guangdong Province (Regional Water Environment Safety and Water Ecological Protection).

References

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